21 May 2002
| Revision History | ||
|---|---|---|
| Revision v1.02 | 2002-05-21 | Revised by: bjh |
| Correct explanation of symbol versioning. Correct author of Linux Device Drivers. Add info about memory allocation penalty of LKM vs bound-in. Add LKM-to-LKM symbol matching requirement. Add open source licensing issue in LKM symbol resolution. Add SMP symbol versioning info. | ||
| Revision v1.01 | 2001-08-18 | Revised by: bjh |
| Add material on various features created in the last few years: kernel module loader, ksymoops symbols, kernel-version-dependent LKM file location. | ||
| Revision v1.00 | 2001-06-14 | Revised by: bjh |
| Initial release. | ||
Copyright and license information, as well as credits, are at the end of this document.
This HOWTO is maintained by Bryan Henderson, bryanh@giraffe-data.com. It was released May 31, 2001. You can get the current version of this HOWTO from the Linux Documentation Project.
If you want to add code to a Linux kernel, the most basic way to do that is to add some source files to the kernel source tree and recompile the kernel. In fact, the kernel configuration process consists mainly of choosing which files to include in the kernel to be compiled.
But you can also add code to the Linux kernel while it is running. A chunk of code that you add in this way is called a loadable kernel module. These modules can do lots of things, but they typically are one of three things: 1) device drivers; 2) filesystem drivers; 3) system calls. The kernel isolates certain functions, including these, especially well so they don't have to be intricately wired into the rest of the kernel.
Loadable kernel modules are often called just kernel modules or just modules, but those are rather misleading terms because there are lots of kinds of modules in the world and various pieces built into the base kernel can easily be called modules. We use the term loadable kernel module or LKM for the particular kinds of modules this HOWTO is about.
Some people think of LKMs as outside of the kernel. They speak of LKMs communicating with the kernel. This is a mistake; LKMs (when loaded) are very much part of the kernel. The correct term for the part of the kernel that is bound into the image that you boot, i.e. all of the kernel except the LKMs, is "base kernel." LKMs communicate with the base kernel.
In some other operating systems, the equivalent of a Linux LKM is called a "kernel extension."
Now what is "Linux"? Well, first of all, the name is used for two entirely different things, and only one of them is really relevant here:
The kernel and related items distributed as a package by Linus Torvalds.
A class of operating systems that traditionally are based on the Linux kernel.
Only the first of these is really useful in discussing LKMs. But even choosing this definition, people are often confused when it comes to LKMs. Is an LKM part of Linux or not? Though an LKM is always part of the kernel, it is part of Linux if it is distributed in the Linux kernel package, and not otherwise. Thus, if you have loaded into your kenel a device driver LKM that came with your device, you can't, strictly speaking, say that your kernel is Linux. Rather, it's a slight extension of Linux. As you might expect, it is commonplace to use the name "Linux" approximately -- Lots of variations on Linux are in use and are widely distributed, and referred to as "Linux." In this document, though, we will stick to the strictest definition in the interest of clarity.
LKMs did not exist in Linux in the beginning. Anything we use an LKM for today was built into the base kernel at kernel build time instead. LKMs have been around at least since Linux 1.2 (1995).
Device drivers and such were always quite modular, though. When LKMs were invented, only a small amount of work was needed on these modules to make them buildable as LKMs. However, it had to be done on each and every one, so it took some time. Since about 2000, virtually everything that makes sense as an LKM has at least had the option of being an LKM.
You often have a choice between putting a module into the kernel by loading it as an LKM or binding it into the base kernel. LKMs have a lot of advantages over binding into the base kernel and I recommend them wherever possible.
One advantage is that you don't have to rebuild your kernel as often. This saves you time and spares you the possibility of introducing an error in rebuilding and reinstalling the base kernel. Once you have a working base kernel, it is good to leave it untouched as long as possible.
Another advantage is that LKMs help you diagnose system problems. A bug in a device driver which is bound into the kernel can stop your system from booting at all. And it can be really hard to tell which part of the base kernel caused the trouble. If the same device driver is an LKM, though, the base kernel is up and running before the device driver even gets loaded. If your system dies after the base kernel is up and running, it's an easy matter to track the problem down to the trouble-making device driver and just not load that device driver until you fix the problem.
LKMs can save you memory, because you have to have them loaded only when you're actually using them. All parts of the base kernel stay loaded all the time. And in real storage, not just virtual storage.
LKMs are much faster to maintain and debug. What would require a full reboot to do with a filesystem driver built into the kernel, you can do with a few quick commands with LKMs. You can try out different parameters or even change the code repeatedly in rapid succession, without waiting for a boot.
LKMs are not slower, by the way, than base kernel modules. Calling either one is simply a branch to the memory location where it resides. [1]
Sometimes you have to build something into the base kernel instead of making it an LKM. Anything that is necessary to get the system up far enough to load LKMs must obviously be built into the base kernel. For example, the driver for the disk drive that contains the root filesystem must be built into the base kernel.
There is a tendency to think of LKMs like user space programs. They do share a lot of their properties, but LKMs are definitely not user space programs. They are part of the kernel. As such, they have free run of the system and can easily crash it.
There are six main things LKMs are used for:
Device drivers. A device driver is designed for a specific piece of hardware. The kernel uses it to communicate with that piece of hardware without having to know any details of how the hardware works. For example, there is a device driver for ATA disk drives. There is one for NE2000 compatible Ethernet cards. To use any device, the kernel must contain a device driver for it.
Filesystem drivers. A filesystem driver interprets the contents of a filesystem (which is typically the contents of a disk drive) as files and directories and such. There are lots of different ways of storing files and directories and such on disk drives, on network servers, and in other ways. For each way, you need a filesystem driver. For example, there's a filesystem driver for the ext2 filesystem type used almost universally on Linux disk drives. There is one for the MS-DOS filesystem too, and one for NFS.
System calls. User space programs use system calls to get services from the kernel. For example, there are system calls to read a file, to create a new process, and to shut down the system. Most system calls are integral to the system and very standard, so are always built into the base kernel (no LKM option). But you can invent a system call of your own and install it as an LKM. Or you can decide you don't like the way Linux does something and override an existing system call with an LKM of your own.
Network drivers. A network driver interprets a network protocol. It feeds and consumes data streams at various layers of the kernel's networking function. For example, if you want an IPX link in your network, you would use the IPX driver.
TTY line disciplines. These are essentially augmentations of device drivers for terminal devices.
Executable interpreters. An executable interpreter loads and runs an executable. Linux is designed to be able to run executables in various formats, and each must have its own executable interpreter.
An LKM lives in a single ELF object file (normally named like "serial.o"). You typically keep all your LKM object files in a particular directory (near your base kernel image makes sense). When you use the insmod program to insert an LKM into the kernel, you give the name of that object file.
For the LKMs that are part of Linux, you build them as part of the same kernel build process that generates the base kernel image. See the README file in the Linux source tree. In short, after you make the base kernel image with a command such as make zImage, you will make all the LKMs with the command
make modules |
This results in a bunch of LKM object files (*.o) throughout the Linux source tree. (In older versions of Linux, there would be symbolic links in the modules directory of the Linux source tree pointing to all those LKM object files). These LKMs are ready to load, but you probably want to install them in some appropriate directory. The conventional place is described in Section 5.5. The command make modules_install will copy them all over to the conventional locations.
Part of configuring the Linux kernel (at build time) is choosing which parts of the kernel to bind into the base kernel and which parts to generate as separate LKMs. In the basic question-and-answer configuration (make config), you are asked, for each optional part of the kernel, whether you want it bound into the kernel (a "Y" response), created as an LKM (an "M" response), or just skipped completely (an "N" response). Other configuration methods are similar.
As explained in Section 2.3, you should have only the bare minimum bound into the base kernel. And only skip completely the parts that you're sure you'll never want. There is very little to lose by building an LKM that you won't use. Some compile time, some disk space, some chance of a problem in the code killing the kernel build. That's it.
As part of the configuration dialog you also must choose whether to use symbol versioning or not. This choice affects building both the base kernel and the LKMs and it is crucial you get it right. See Section 6.
LKMs that are not part of Linux (i.e. not distributed with the Linux kernel) have their own build procedures which I will not cover. The goal of any such procedure, though, is always to end up with an ELF object file.
You don't necessarily have to rebuild all your LKMs and your base kernel image at the same time (e.g. you could build just the base kernel and use LKMs you built earlier with it) but it is always a good idea. See Section 6.
The programs you need to load and unload and otherwise work with LKMs are in the package modutils. You can find this package in this directory.
This package contains the following programs to help you use LKMs:
Insert an LKM into the kernel.
Remove an LKM from the kernel.
Determine interdependencies between LKMs.
Kerneld daemon program
Display symbols that are exported by the kernel for use by new LKMs.
List currently loaded LKMs.
Display contents of .modinfo section in an LKM object file.
Insert or remove an LKM or set of LKMs intelligently. For example, if you must load A before loading B, Modprobe will automatically load A when you tell it to load B.
Changes to the kernel often require changes to modutils, so be sure you're using a current version of modutils whenever you upgrade your kernel. modutils is always backward compatible (it works with older kernels), so there's no such thing as having too new a modutils.
Warning: modprobe invokes insmod and has its location hardcoded as /sbin/insmod. There may be other instances in modutils of the PATH not being used to find programs. So either modify the source code of modutils before you build it, or make sure you install the programs in their conventional directories.
The basic programs for inserting and removing LKMs are insmod and rmmod. See their man pages for details.
Inserting an LKM is conceptually easy: Just type, as superuser, a command like
insmod serial.o |
However, I would be misleading you if I said the command just works. It is very common, and rather maddening, for the command to fail either with a message about a module/kernel version mismatch or a pile of unresolved symbols.
If it does work, though, the way to prove to yourself that you know what you're doing is to look at /proc/modules as described in Section 5.4.
Now lets look at a more difficult insertion. If you try
insmod msdos.o |
msdos.o: unresolved symbol fat_date_unix2dos msdos.o: unresolved symbol fat_add_cluster1 msdos.o: unresolved symbol fat_put_super ... |
This is because msdos.o contains external symbol references to the symbols mentioned and there are no such symbols exported by the kernel. To prove this, do a
cat /proc/ksyms |
How do you get it into the list? By loading another LKM, one which defines those symbols and exports them. In this case, it is the LKM in the file fat.o. So do
insmod fat.o |
insmod msdos.o |
msdos 5632 0 (unused) fat 30400 0 [msdos] |
How did I know fat.o was the module I was missing? Just a little ingenuity. A more robust way to address this problem is to use depmod and modprobe instead of insmod, as discussed below.
When your symbols look like "fat_date_unix2dos_R83fb36a1", the problem may be more complex than just getting prerequisite LKMs loaded. See Section 6.
When the error message is "kernel/module version mismatch," see Section 6.
Often, you need to pass parameters to the LKM when you insert it. For example, a device driver wants to know the address and IRQ of the device it is supposed to drive. Or the network driver wants to know how much diagnostic tracing you want it to do. Here is an example of that:
insmod ne.o io=0x300 irq=11 |
Here, I am loading the device driver for my NE2000-like Ethernet adapter and telling it to drive the Ethernet adapter at IO address 0x300, which generates interrupts on IRQ 11.
There are no standard parameters for LKMs and very few conventions. Each LKM author decides what parameters insmod will take for his LKM. Hence, you will find them documented in the documentation of the LKM. This HOWTO also compiles a lot of LKM parameter information in Section 13. For general information about LKM parameters, see Section 8.
To remove an LKM from the kernel, the command is like
rmmod ne |
There is a command lsmod to list the currently loaded LKMs, but all it does is dump the contents of /proc/modules, with column headings, so you may just want to go to the horse's mouth and forget about lsmod.
A common error is to try to insert an object file which is not an LKM. For example, you configure your kernel to have the USB core module bound into the base kernel instead of generated as an LKM. In that case, you end up with a file usbcore.o, which looks pretty much the same as the usbcore.o you would get if you built it as an LKM. But you can't insmod that file.
So do you get an error message telling you that you should have configured the kernel to make USB core function an LKM? Of course not. This is Unix, and explanatory error messages are seen as a sign of weakness. The error message is
$ insmod usbcore.o usbcore.o: couldn't find the kernel version this module was compiled for |
What insmod is telling you is that it looked in usbcore.o for a piece of information any legitimate LKM would have -- the kernel version with which the LKM was intended to be used -- and it didn't find it. We know now that the reason it didn't find it is that the file isn't an LKM. See Section 10.2.
Once you have module loading and unloading figured out using insmod and rmmod, you can let the system do more of the work for you by using the higher level program modprobe. See the modprobe man page for details.
The main thing that modprobe does is automatically load the prerequisites of an LKM you request. It does this with the help of a file that you create with depmod and keep on your system.
Example:
modprobe msdos |
This performs an insmod of msdos.o, but before that does an insmod of fat.o, since you have to have fat.o loaded before you can load msdos.o.
The other major thing modprobe does for you is to find the object module containing the LKM given just the name of the LKM. For example, modprobe msdos might load /lib/2.4.2-2/fs/msdos.o. Check out the man pages for modprobe and the configuration file modules.conf (usually /etc/modules.conf) for details on the search rules modprobe uses.
depmod scans your LKM object files (typically all the .o files in the appropriate /lib/modules subdirectory) and figures out which LKMs prerequire (refer to symbols in) other LKMs. It generates a dependency file (typically named modules.dep), which you normally keep in /lib/modules for use by modprobe.
You can use modprobe to remove stacks of LKMs as well.
Via the LKM configuration file (typically /etc/modules.conf), you can fine tune the dependencies and do other fancy things to control LKM selections. And you can specify programs to run when you insert and remove LKMs, for example to initialize a device driver.
If you are maintaining one system and memory is not in short supply, it is probably easier to avoid modprobe and the various files and directories it needs, and just do raw insmods in a startup script.
You can cause an LKM to be loaded automatically when the kernel first needs it. You do this with either a kerneld daemon or with the more recent invention, the kernel module loader, which is part of Linux.
As an example, let's say you run a program that executes an open system call for a file in an MS-DOS filesystem. But you don't have a filesystem driver for the MS-DOS filesystem either bound into your base kernel or loaded as an LKM. So the kernel does not know how to access the file you're opening on the disk.
The kernel recognizes that it has no filesystem driver for MS-DOS, but that one of the two automatic module loading facilities are available and uses it to cause the LKM to be loaded. The kernel then proceeds with the open.
Both kerneld and the kernel module loader use modprobe, ergo insmod, to insert LKMs.
kerneld is explained at length in the Kerneld mini-HOWTO, available from the Linux Documentation Project.
kerneld is a user process, which runs the kerneld program from the modutils package. kerneld sets up an IPC message channel with the kernel. When the kernel needs an LKM, it sends a message on that channel to kerneld and kerneld runs modprobe to load the LKM, then sends a message back to the kernel to say that it is done.
There is some documentation of the kernel module loader in the file Documentation/kmod.txt in the Linux source tree. As of this writing, this section is more complete and accurate than that file. You can also look at its source code in kernel/kmod.c.
The kernel module loader is an optional part of the Linux kernel. You get it if you select the CONFIG_KMOD feature when you configure the kernel at build time.
When a kernel that has the kernel module loader needs an LKM, it creates a user process (owned by the superuser, though) that executes modprobe to load the LKM, then exits. By default, it finds modprobe as /sbin/modprobe, but you can set up any program you like as modprobe by writing its file name to /proc/sys/kernel/modprobe. For example:
$ echo "sbin/mymodprobe" >/proc/sys/kernel/modprobe |
The kernel module loader passes the following arguments to modprobe: Argument Zero is the full file name of modprobe. The regular arguments are -s, -k, and the name of the LKM that the kernel wants. -s is the user-hostile form of --syslog; -k is the cryptic way to say --autoclean. I.e. messages from modprobe will go to syslog and the loaded LKM will have the "autoclean" flag set.
The kernel module loader runs modprobe with the following environment variables (only): HOME=/; TERM=linux; PATH=/sbin:/usr/sbin:/bin:/usr/bin.
The kernel module loader was new in Linux 2.2 and was designed to take the place of kerneld. It does not, however, have all the features of kerneld.
In Linux 2.2, the kernel module loader creates the above mentioned process directly. In Linux 2.4, the kernel module loader submits the module loading work to Keventd and it runs as a child process of Keventd.
The kernel module loader is a pretty strange beast. It violates layering as Unix programmers generally understand it and consequently is inflexible, hard to understand, and not robust. Many system designers would bristle just at the fact that it has the PATH hardcoded. You may prefer to use kerneld instead, or not bother with automatic loading of LKMs at all.
Each loaded LKM has an autoclean flag which can be set or unset. You control this flag with parameters to the init_module system call. Assuming you do that via insmod, you use the --autoclean option.
You can see the state of the autoclean flag in /proc/modules. Any LKM that has the flag set has the legend autoclean next to it.
The purpose of the autoclean flag is to be let you automatically remove LKMs that haven't been used in a while (typically 1 minute). So by using automatic module loading and unloading, you can keep only parts of the kernel that are presently needed loaded, and save memory.
This is less important than it once was, with memory being much cheaper. If you don't need to save memory, you shouldn't bother with the complexity of module loader processes. Just load everything you might need via an initialization script and keep it loaded.
There is a form of the delete_module system call that says, "remove all LKMs that have the autoclean flag set and haven't been used in a while." Kerneld typically calls this once per minute. You can call it explicitly with an rmmod --all command.
As the kernel module loader does not do any removing of LKMs, if you use that you might want to have a cron job that does a rmmod --all periodically.
To see the presently loaded LKMs, do
cat /proc/modules |
You see a line like
serial 24484 0 |
The left column is the name of the LKM, which is normally the name of the object file from which you loaded it, minus the ".o" suffix. You can, however, choose any name you like with an option on insmod.
The "24484" is the size in bytes of the LKM in memory.
The "0" is the use count. It tells how many things presently depend on the LKM being loaded. Typical "things" are open devices or mounted fileystems. It is important because you cannot remove an LKM unless the use count is zero. The LKM itself maintains this count, but the module manager uses it to decide whether to permit an unload.
There is an exception to the above description of the use count. You may see -1 in the use count column. What that means is that this LKM does not use use counts to determine when it is OK to unload. Instead, the LKM has registered a subroutine that the module manager can call that will return an indication of whether or not it is OK to unload the LKM. In this case, the LKM ought to provide you with some custom interface, and some documentation, to determine when the LKM is free to be unloaded.
The LKM world is flexible enough that the files you need to load could live just about anywhere on your system, but there is a convention that most systems follow: The LKM .o files are in the directory /lib/modules, divided into subdirectories. There is one subdirectory for each version of the kernel, since LKMs are specific to a kernel (see Section 6). Each subdirectory contains a complete set of LKMs.
The subdirectory name is the value you get from the uname --release command, for example 2.2.19. Section 6.3 tells how you control that value.
When you build Linux, a standard make modules and make modules_install should install all the LKMs that are part of Linux in the proper release subdirectory.
If you build a lot of kernels, another organization may be more helpful: keep the LKMs together with the base kernel and other kernel-related files in a subdirectory of /boot. The only drawback of this is that you cannot have /boot reside on a tiny disk partition. In some systems, /boot is on a special tiny "boot partition" and contains only enough files to get the system up to the point that it can mount other filesystems.
msdos.o: unresolved symbol fat_date_unix2dos msdos.o: unresolved symbol fat_add_cluster1 msdos.o: unresolved symbol fat_put_super ... |
The designers of loadable kernel modules realized there would be a problem with having the kernel in multiple files, possibly distributed independently of one another. What if the LKM mydriver.o was written and compiled to work with the Linux 1.2.1 base kernel, and then someone tried to load it into a Linux 1.2.2 kernel? What if there was a change between 1.2.1 and 1.2.2 in the way a kernel subroutine that mydriver.o calls works? These are internal kernel subroutines, so what's to stop them from changing from one release to the next? You could end up with a broken kernel.
To address this problem, the creators of LKMs endowed them with a kernel version number. The special .modinfo section of the mydriver.o object file in this example has "1.2.1" in it because it was compiled using header files from Linux 1.2.1. Try to load it into a 1.2.2 kernel and insmod notices the mismatch and fails, telling you you have a kernel version mismatch.
But wait. What's the chance that there really is an incompatibility between Linux 1.2.1 and 1.2.2 that will affect mydriver.o? mydriver.o only calls a few subroutines and accesses a few data structures. Surely they don't change with every minor release. Must we recompile every LKM against the header files for the particular kernel into which we want to insert it?
To ease this burden, insmod has a -f option that "forces" insmod to ignore the kernel version mismatch and insert the module anyway. Because it is so unusual for there to be a significant difference between any two kernel versions, I recommend you always use -f. You will, however, still get a warning message about the mismatch. There's no way to shut that off.
But LKM designers still wanted to address the problem of incompatible changes that do occasionally happen. So they invented a very clever way to allow the LKM insertion process to be sensitive to the actual content of each kernel subroutine the LKM uses. It's called symbol versioning (or sometimes less clearly, "module versioning."). It's optional, and you select it when you configure the kernel via the "CONFIG_MODVERSIONS" kernel configuration option.
When you build a base kernel or LKM with symbol versioning, the various symbols exported for use by LKMs get defined as macros. The definition of the macro is the same symbol name plus a hexadecimal hash value of the parameter and return value types for the subroutine named by the symbol (based on an analysis by the program genksyms of the source code for the subroutine). So let's look at the register_chrdev subroutine. register_chrdev is a subroutine in the base kernel that device driver LKMs often call. With symbol versioning, there is a C macro definition like
#define register_chrdev register_chrdev_Rc8dc8350 |
This macro definition is in effect both in the C source file that defines register_chrdev and in any C source file that refers to register_chrdev, so while your eyes see register_chrdev as you read the code, the C preprocessor knows that the function is really called register_chrdev_Rc8dc8350.
What is the meaning of that garbage suffix? It is a hash of the data types of the parameters and return value of register_chrdev. No two combinations of parameter and return value types have the same hash value.
So let's say someone adds a paramater to register_chrdev between Linux 1.2.1 and Linux 1.2.2. In 1.2.1, register_chrdev is a macro for register_chrdev_Rc8dc8350, but in 1.2.2, it is a macro for register_chrdev_R12f8dc01. In mydriver.o, compiled with Linux 1.2.1 header files, there is an external reference to register_chrdev_Rc8dc8350, but there is no such symbol exported by the 1.2.2 base kernel. Instead, the 1.2.2 base kernel exports a symbol register_chrdev_R12f8dc01.
So if you try to insmod this 1.2.1 mydriver.o into this 1.2.2 base kernel, you will fail. And the error message isn't one about mismatched kernel versions, but simply "unresolved symbol reference."
As clever as this is, it actually works against you sometimes. The way genksyms works, it often generates different hash values for parameter lists that are essentially the same.
And symbol versioning doesn't even guarantee compatibility. It catches only a small subset of the kinds of changes in the definition of a function that can make it not backward compatible. If the way register_chrdev interprets one of its parameters changes in a non-backward-compatible way, its version suffix won't change -- the parameter still has the same C type.
And there's no way an option like -f on insmod can get around this.
So it is generally not wise to use symbol versioning.
Of course, if you have a base kernel that was compiled with symbol versioning, then you must have all your LKMs compiled likewise, and vice versa. Otherwise, you're guaranteed to get those "unresolved symbol reference" errors.
Now that we've seen how you often have different versions of an LKM for different base kernels, the question arises as to what to do about a system that has multiple kernel versions (i.e. you can choose a kernel at boot time). You want to make sure that the LKMs built for Kernel A get inserted when you boot Kernel A, but the LKMs built for Kernel B get inserted when you boot Kernel B.
In particular, whenever you upgrade your kernel, if you're smart, you keep both the new kernel and the old kernel on the system until you're sure the new one works.
The most common way to do this is with the LKM-hunting feature of modprobe. modprobe understands the conventional LKM file organization described in Section 5.5 and loads LKMs from the appropriate subdirectory depending on the kernel that is running.
You set the uname --release value, which is the name of the subdirectory in which modprobe looks, by editing the main kernel makefile when you build the kernel and setting the VERSION, PATCHLEVEL, SUBLEVEL, and EXTRAVERSION variables at the top.
The same ways an LKM must be compatible with the base kernel, it must be compatible with any LKMs which it accesses (e.g. the first LKM calls a subroutine in the second). The preceding sections limit their discussions to the base kernel just to keep it simple.
For most systems, the ATA disk device driver must be bound into the base kernel because the root filesystem is on an ATA disk [2] and the kernel cannot mount the root filesystem, much less read any LKMs from it, without the ATA disk driver. But if you really want the device driver for your root filesystem to be an LKM, here's how to do it with Initrd:
"Initrd" is the name of the "initial ramdisk" feature of Linux. With this, you have your loader (probably LILO) load a filesystem into memory (as a ramdisk) before starting the kernel. When it starts the kernel, it tells it to mount the ramdisk as the root filesystem. You put the disk device driver for your real root filesystem and all the software you need to load it in that ramdisk filesystem. Your startup programs (which live in the ramdisk) eventually mount the real (disk) filesystem as the root filesystem. Note that a ramdisk doesn't require any device driver.
This does not free you, however, from having to bind into the base kernel 1) the filesystem driver for the filesystem in your ramdisk, and 2) the executable interpreter for the programs in the ramdisk.
It is useful to compare parameters that get passed to LKMs and parameters that get passed to modules that are bound into the base kernel, especially since modules often can be run either way.
We've seen above that you pass parameters to an LKM by specifying something like io=0x300 on the insmod command. For a module that is bound into the base kernel, you pass parameters to it via the kernel boot parameters. One common way to specify kernel boot parameters is at a lilo boot prompt. Another is with an append statement in the lilo configuration file.
The kernel initializes an LKM at the time you load it. It initializes a bound-in module at boot time.
Since there is only one string of kernel boot parameters, you need some way within that string to identify which parameters go to which modules. The rule for this is that if there is a module named xyz, then a kernel boot parameter named xyz is for that module. The value of a kernel boot parameter is an arbitrary string that makes sense only to the module.
This is why you sometimes see an LKM whose only parameter is its own name. E.g. you load the Mitsumi CDROM driver with a command like
insmod mcd mcd=0x340 |
Some LKMs are set up to retain information from one load to the next. This is called persistent data. When you remove one of these LKMs with rmmod, rmmod extracts certain values from the LKM's working storage and stores them in a file. When you next insert the LKM with insmod, insmod reads the persistent data from the file and inserts it into the LKM.
See the --persist option on insmod and rmmod.
Persistent data was introduced in November 2000.
insmod makes an init_module system call to load the LKM into kernel memory. Loading it is the easy part, though. How does the kernel know to use it? The answer is that the init_module system call invokes the LKM's initialization routine right after it loads the LKM. insmod passes to init_module the address of the subroutine in the LKM named init_module as its initialization routine.
(This is confusing -- every LKM has a subroutine named init_module, and the base kernel has a system call by that same name, which is accessible via a subroutine in the standard C library also named init_module).
The LKM author set up init_module to call a kernel function that registers the subroutines that the LKM contains. For example, a character device driver's init_module subroutine might call the kernel's register_chrdev subroutine, passing the major and minor number of the device it intends to drive and the address of its own "open" routine among the arguments. register_chrdev records in base kernel tables that when the kernel wants to open that particular device, it should call the open routine in our LKM.
But the astute reader will now ask how the LKM's init_module subroutine knew the address of the base kernel's register_chrdev subroutine. This is not a system call, but an ordinary subroutine bound into the base kernel. Calling it means branching to its address. So how does our LKM, which was not compiled anywhere near the base kernel, know that address? The answer to this is insmod relocation. insmod functions as a relocating linker/loader. The LKM object file contains an external reference to the symbol register_chrdev. insmod does a query_module system call to find out the addresses of various symbols that the existing kernel exports. register_chrdev is among these. query_module returns the address for which register_chrdev stands and insmod patches that into the LKM where the LKM refers to register_chrdev.
If you want to see the kind of information insmod can get from a query_module system call, look at the contents of /proc/ksyms.
Note that some LKMs call subroutines in other LKMs. They can do this because of the __ksymtab and .kstrtab sections in the LKM object files. These sections together list the external symbols within the LKM object file that are supposed to be accessible by other LKMs inserted in the future. insmod looks at __ksymtab and .kstrtab and tells the kernel to add those symbols to its exported kernel symbols table.
To see this for yourself, insert the LKM msdos.o and then notice in /proc/ksyms the symbol fat_add_cluster (which is the name of a subroutine in the fat.o LKM). Any subsequently inserted LKM can branch to fat_add_cluster, and in fact msdos.o does just that.
An ELF object file consists of various named sections. Some of them are basic parts of an object file, for example the .text section contains executable code that a loader loads. But you can make up any section you want and have it used by special programs. For the purposes of Linux LKMs, there is the .modinfo section. An LKM doesn't have to have a section named .modinfo to work, but the macros you're supposed to use to code an LKM cause one to be generated, so they generally do.
To see the sections of an object file, including the .modinfo section if it exists, use the objdump program. For example:
To see all the sections in the object file for the msdos LKM:
objdump msdos.o --section-headers |
objdump msdos.o --full-contents --section=.modinfo |
You can use the modinfo program to interpret the contents of the .modinfo section.
So what is in the .modinfo section and who uses it? insmod uses the .modinfo section for the following:
It contains the kernel release number for which the module was built. I.e. of the kernel source tree whose header files were used in compiling the module.
insmod uses that information as explained in Section 6.
It describes the form of the LKM's parameters. insmod uses this information to format the parameters you supply on the insmod command line into data structure initial values, which insmod inserts into the LKM as it loads it.
Two other sections you often find in an LKM object file are named __ksymtab and .kstrtab. Together, they list symbols in the LKM that should be accessible (exported) to other parts of the kernel. A symbol is just a text name for an address in the LKM. LKM A's object file can refer to an address in LKM B by name (say, getBinfo"). When you insert LKM A, after having inserted LKM B, insmod can insert into LKM A the actual address within LKM B where the data/subroutine named getBinfo is loaded.
See Section 10.1 for more mind-numbing details of symbol binding.
insmod adds a bunch of exported symbols to the LKM as it loads it. These symbols are all intended to help ksymoops do its job. ksymoops is a program that interprets and "oops" display. And "oops" display is stuff that the Linux kernel displays when it detects an internal kernel error (and consequently terminates a process). This information contains a bunch of addresses in the kernel, in hexadecimal.
ksymoops looks at the hexadecimal addresses, looks them up in the kernel symbol table (which you see in /proc/ksyms, and translates the addresses in the oops message to symbolic addresses, which you might be able to look up in an assembler listing.
So lets say you have an LKM crash on you. The oops message contains the address of the instruction that choked, and what you want ksymoops to tell you is 1) in what LKM is that instruction, and 2) where is the instruction relative to an assembler listing of that LKM? Similar questions arise for the data addresses in the oops message.
To answer those questions, ksymoops must be able to get the loadpoints and lengths of the various sections of the LKM from the kernel symbol table.
Well, insmod knows those addresses, so it just creates symbols for them and includes them in the symbols it loads with the LKM.
In particular, those symbols are named (and you can see this for yourself by looking at /proc/ksyms):
__insmod_name_Ssectionname_Llength
name is the LKM name (as you would see in /proc/modules.
sectionname is the section name, e.g. .text (don't forget the leading period).
length is the length of the section, in decimal.
The value of the symbol is, of course, the address of the section.
Insmod also adds a pretty useful symbol that tells from what file the LKM was loaded. That symbol's name is
__insmod_name_Ofilespec_Mmtime_Vversion
name is the LKM name, as above.
filespec is the file specification that was used to identify the file containing the LKM when it was loaded. Note that it isn't necessarily still under that name, and there are multiple file specifications that might have been used to refer to the same file. For example, ../dir1/mylkm.o and /lib/dir1/mylkm.o.
mtime is the modification time of that file, in the standard Unix representation (seconds since 1969), in hexadecimal.
version tells the kernel version level for which the LKM was built (same as in the .modinfo section). It is the value of the macro LINUX_VERSION_CODE in Linux's linux/version.h file. For example, 132101.
The value of this symbol is meaningless.
insmod adds another symbol, similar to the ksymoops symbols. This one tells where the persistent data lives in the LKM, which rmmod needs to know in order to save the persistent data.
__insmod_name_Plength
This section is about how Linux allocates memory in which to load an LKM. It is not about how an LKM dynamically allocates memory, which is the same as for any other part of the kernel.
The memory where an LKM resides is a little different from that where the base kernel resides. The base kernel is always loaded into one big contiguous area of real memory, whose real addresses are equal to is virtual addresses. That's possible because the base kernel is the first thing ever to get loaded (besides the loader) -- it has a wide open empty space in which to load. And since the Linux kernel is not pageable, it stays in it's homestead forever.
By the time you load an LKM, real memory is all fragmented -- you can't simply add the LKM to the end of the base kernel. But the LKM needs to be in contiguous virtual memory, so Linux uses vmalloc to allocate a contiguous area of virtual memory (in the kernel address space), which is probably not contiguous in real memory. But the memory is still not pageable. The LKM gets loaded into real page frames from the start, and stays in those real page frames until it gets unloaded.
Some CPUs can take advantage of the properties of the base kernel to effect faster access to base kernel memory. For example, on one machine, the entire base kernel is covered by one page table entry and consequently one entry in the translation lookaside buffer (TLB). Naturally, that TLB entry is virtually always present. For LKMs on this machine, there is a page table entry for each memory page into which the LKM is loaded. Much more often, the entry for a page is not in the TLB when the CPU goes to access it, which means a slower access.
This effect is probably trivial.
It is also said that PowerPC Linux does something with its address translation so that transferring between accessing base kernel memory to accessing LKM memory is costly. I don't know anything solid about that.
The base kernel contains within its prized contiguous domain a large expanse of reusable memory -- the kmalloc pool. In Linux 2.4, at the end of 2001, there was a proposal to make the module loader try first to get contiguous memory from that pool into which to load an LKM and only if a large enough space was not available, go to the vmalloc space. That function may be in some versions of Linux.
If you're interested in the internal workings of the Linux kernel with respect to LKMs, this section can get you started. You should not need to know any of this in order to develop, build, and use LKMs.
The code to handle LKMs is in the source files kernel/module.c in the Linux source tree.
The kernel module loader (see Section 5.3) lives in kernel/kmod.c.
(Ok, that wasn't much of a start, but at least I have a framework here for adding this information in the future).
The Linux Kernel Module Programming Guide by Ori Pomerantz is a complete explanation of writing your own LKM. This book is also available in print.
It is, however, a little out of date and contains an error or two. Here are a few things about writing an LKM that aren't in there.
The simple hello.c program has a small bug that causes it to generate a warning about an implicit declaration of printk(). The warning is innocuous.
The program is also more complicated than it needs to be with current Linux and depends on your having kernel messaging set up a certain way on your system to see it work. Finally, the program requires you to include -D options on your compile command to work, because it does not define some macros in the source code, where the definitions belong.
Here is an improved version of hello.c. Compile this with the simple command
$ gcc -c -Wall hello.c |
/* hello.c
*
* "Hello, world" - the loadable kernel module version.
*
* Compile this with
*
* gcc -c hello.c -Wall
*/
/* Declare what kind of code we want from the header files */
#define __KERNEL__ /* We're part of the kernel */
#define MODULE /* Not a permanent part, though. */
/* Standard headers for LKMs */
#include <linux/modversions.h>
#include <linux/module.h>
#define _LOOSE_KERNEL_NAMES
/* With some combinations of Linux and gcc, tty.h will not compile if
you don't define _LOOSE_KERNEL_NAMES. It's a bug somewhere.
*/
#include <linux/tty.h> /* console_print() interface */
/* Initialize the LKM */
int init_module()
{
console_print("Hello, world - this is the kernel speaking\n");
/* More normal is printk(), but there's less that can go wrong with
console_print(), so let's start simple.
*/
/* If we return a non zero value, it means that
* init_module failed and the LKM can't be loaded
*/
return 0;
}
/* Cleanup - undo whatever init_module did */
void cleanup_module()
{
console_print("Short is the life of an LKM\n");
} |
The most popular book on writing device drivers is O'Reilly's Linux Device Drivers by Alessandro Rubini and Jonathan Corbet.
Even if you're writing an LKM that isn't a device driver, you can learn a lot from this book that will help you.
The first edition of this book covers Linux 2.0, with notes about differences in 2.2. The second edition (June 2001) covers Linux 2.4.
This book is available under the FDL. You can read it at http://www.xml.com/ldd/chapter/book/.
In the original design, the LKM increments and decrements its use count to tell the module manager whether it is OK to unload it. For example, if it's a filesystem driver, it would increment the use count when someone mounts a filesystem of the type it drives, and decrement it at unmount time.
Now, there is a more flexible alternative. Your LKM can register a function that the module manager will call whenever it wants to know if it is OK to unload the module. If the function returns a true value, that means the LKM is busy and cannot be unloaded. If it returns a false value, the LKM is idle and can be unloaded. The module manager holds the big kernel lock from before calling the module-busy function until after its cleanup subroutine returns or sleeps, and unless you've done something odd, that should mean that your LKM cannot become busy between the time that you report "not busy" and the time you clean up.
So how do you register the module-busy function? By putting its address in the unfortunately named can_unload field in the module descriptor ("struct module"). The name is truly unfortunate because the boolean value it returns is the exact opposite of what "can unload" means: true if the module manager cannot unload the LKM.
The module manager ensures that it does not attempt to unload the module before its initialization subroutine has returned or sleeps, so you are safe in setting the can_unload field anywhere in the initialization subroutine except after a sleep.
For modules that are part of Linux (i.e. distributed with the base kernel), you can sometimes find documentation in the Documentation subdirectory of the Linux source code.
Many LKMs can be alternatively bound into the base kernel. If you do that, you will pass parameters to them via the kernel "command line," which in its most basic form means via a prompt at boot time. The BootPrompt HOWTO by Paul Gortmaker <Paul.Gortmaker@anu.edu.au> will help you with that. It is available from the Linux Documentation Project.
Don't forget that the source code of Linux and any LKM is always the documentation of last resort, and the most trustworthy.
In this chapter, I document individual LKMs. Where possible, I do this by reference to more authoritative documentation for the particular LKM (probably maintained by the same person who maintains the LKM code).
You must have at least one executable interpreter bound into the base kernel, because in order to load an executable interpreter LKM, you have to run an executable and something has to interpret that executable.
That one bound-in executable interpreter is almost certainly the ELF interpreter, since virtually all executables in a Linux system are ELF.
Historical note: Before ELF existed on Linux (c. 1995), the normal executable format was a.out. For a while, part ELF/part a.out systems were common. Some still exist.
a.out is the venerable executable format that was common in Unix's early history and originally Linux's only executable format. To this day, the default name of the executable output file of the GNU compiler is a.out (regardless of what it's format is).
If you try to run an a.out executable without this, your exec system call fails with a "cannot execute binary file" error.
There are no LKM parameters.
Example:
modprobe binfmt_aout |
ELF is the normal executable format on Linux systems.
It's almost inconceivable that you wouldn't have this executable interpreter bound into the base kernel (if for no other reason that your insmod is probably an ELF executable). However, it is conceptually possible to leave it out of the base kernel and insert it as an LKM.
There are no LKM parameters.
Example:
modprobe binfmt_elf |
Java is a relatively modern object oriented programming language. Java programs are traditionally compiled into "Java bytecode" which is meant to be interpreted by a Java bytecode interpreter. The point of this new object language is that the bytecode object files are portable: Although different systems require different object formats, as long as each system has a bytecode interpreter, it can run bytecode object files. (This only works for a while, of course. If portability were that easy, all systems today would use the same object format anyway).
While the intent was that the bytecode interpreter would run as a user space program, with this LKM you can make the Linux kernel interpret Java bytecode like any other executable format. So you can run a program compiled from Java the same as you would run a program compiled from C (e.g. type its name at a command shell prompt).
In practice, the advantages of the intermediate bytecode language have not been proven and it is quite common to compile Java directly to a more traditional executable format, such as ELF. If you do that, you don't need binfmt_java.
There are no LKM parameters.
Example:
modprobe binfmt_java |
This is the device driver for floppy disks. You need this in order to access a floppy disk in any way.
This LKM is documented in the file README.fd in the linux/drivers/block directory of the Linux source tree. For detailed up to date information refer directly to this file.
Note that if you boot (or might boot) from a floppy disk or with a root filesystem on a floppy disk, you must have this driver bound into the base kernel, because your system will need it before it has a chance to insert the LKM.
Example:
modprobe floppy 'floppy="daring two_fdc 0,thinkpad 0x8,fifo_depth"' |
There is only one LKM parameter: floppy. But it contains many subparameters. The reason for this unusual parameter format is to be consistent with the way you would specify the same things in the kernel boot parameters if the driver were bound into the base kernel.
The value of floppy is a sequence of blank-delimited words. Each of those words is one of the following sequences of comma-delimited words:
Sets the bit mask of allowed drives to allow only units 0 and 1. Obsolete, as this is the default setting anyways
Tells the floppy driver that you have a well behaved floppy controller. This allows more efficient and smoother operation, but may fail on certain controllers. This may speed up certain operations.
Tells the floppy driver that your floppy controller should be used with caution.
Tells the floppy driver that you have only floppy controller (default).
Tells the floppy driver that you have two floppy controllers. The second floppy controller is assumed to be at address. This option is not needed if the second controller is at address 0x370, and if you use the 'cmos' option
Like above, but with default address
Tells the floppy driver that you have an IBM Thinkpad model notebook computer. Thinkpads use an inverted convention for the disk change line.
Tells the floppy driver that you don't have a Thinkpad.
Tells the floppy driver not to use DMA for data transfers. This is needed on HP Omnibooks, which don't have a workable DMA channel for the floppy driver. This option is also useful if you frequently get "Unable to allocate DMA memory" messages. Indeed, DMA memory needs to be continuous in physical memory, and is thus harder to find, whereas non-DMA buffers may be allocated in virtual memory. However, I advise against this if you have an FDC without a FIFO (8272A or 82072). 82072A and later are OK). You also need at least a 486 to use nodma. If you use nodma mode, I suggest you also set the FIFO threshold to 10 or lower, in order to limit the number of data transfer interrupts.
If you have a FIFO-able FDC, the floppy driver automatically falls back on non DMA mode if it can't find any DMA-able memory. If you want to avoid this, explicitly specify "yesdma".
Same as nodma.
Tells the floppy driver that a workable DMA channel is available (the default).
Disables the FIFO entirely. This is needed if you get "Bus master arbitration error" messages from your Ethernet card (or from other devices) while accessing the floppy.
Enables the FIFO (default)
Sets the FIFO threshold. This is mostly relevant in DMA mode. If this is higher, the floppy driver tolerates more interrupt latency, but it triggers more interrupts (i.e. it imposes more load on the rest of the system). If this is lower, the interrupt latency should be lower too (faster processor). The benefit of a lower threshold is fewer interrupts.
To tune the fifo threshold, switch on over/underrun messages using 'floppycontrol --messages'. Then access a floppy disk. If you get a huge amount of "Over/Underrun - retrying" messages, then the fifo threshold is too low. Try with a higher value, until you only get an occasional Over/Underrun.
The value must be between 0 and 0xf, inclusive.
As you insert and remove the LKM to try different values, remember to redo the 'floppycontrol --messages' every time you insert the LKM. You shouldn't normally have to tune the fifo, because the default (0xa) is reasonable.
Sets the CMOS type of drive to type. This is mandatory if you have more than two floppy drives (only two can be described in the physical CMOS), or if your BIOS uses non-standard CMOS types. The CMOS types are:
Use the value of the physical CMOS
5 1/4 DD
5 1/4 HD
3 1/2 DD
3 1/2 HD
3 1/2 ED
3 1/2 ED
unknown or not installed
(Note: there are two valid types for ED drives. This is because 5 was initially chosen to represent floppy tapes, and 6 for ED drives. AMI ignored this, and used 5 for ED drives. That's why the floppy driver handles both)
Print a warning message when an unexpected interrupt is received. (default behavior)
Don't print a message when an unexpected interrupt is received. This is needed on IBM L40SX laptops in certain video modes. (There seems to be an interaction between video and floppy. The unexpected interrupts only affect performance, and can safely be ignored.)
Same as no_unexpected_interrupts.
Don't use the disk change line, but assume that the disk was changed whenever the device node is reopened. Needed on some boxes where the disk change line is broken or unsupported. This should be regarded as a stopgap measure, indeed it makes floppy operation less efficient due to unneeded cache flushings, and slightly more unreliable. Please verify your cable, connection and jumper settings if you have any DCL problems. However, some older drives, and also some laptops are known not to have a DCL.
Print debugging messages
Print informational messages for some operations (disk change notifications, warnings about over and underruns, and about autodetection)
Uses a less noisy way to clear the disk change line (which doesn't involve seeks). Implied by daring.
Tells the driver to expect interrupts on IRQ nr instead of the conventional IRQ 6.
Tells the driver to use DMA channel nr instead of the conventional DMA channel 2.
Use PS/2 stepping rate: PS/2 floppies have much slower step rates than regular floppies. It's been recommended that take about 1/4 of the default speed in some more extreme cases.
Sets the bitmask of allowed drives to mask. By default, only units 0 and 1 of each floppy controller are allowed. This is done because certain non-standard hardware (ASUS PCI motherboards) mess up the keyboard when accessing units 2 or 3. This option is somewhat obsoleted by the 'cmos' option.
Sets the bitmask of allowed drives to all drives. Use this if you have more than two drives connected to a floppy controller.
This module lets you mount a filesystem that is stored in a regular file (in another filesystem). One use of this is to test an ISO 9660 filesystem before irreversibly burning it onto a CD. You build the filesystem in a 650 MB regular file. That file will be the input to the CD burning program. But you can define that file as a loopback device and then mount the filesystem right from the file. It can also give you a handy way to transmit collections of files over a network. It's like a tar file, only you don't have to pack and unpack it -- you just mount the original file.
You can also encrypt or compress the file. To do that, you need a recent version of mount and other patches for DES and IDEA. They can
Do not confuse these loop devices with the "loopback device" used for network connections from the machine to itself. That isn't actually a device at all - it's a network interface.
Example:
modprobe loop |
The module has no parameters.
This driver lets you combine several disk partitions into one logical block device.
If you use this, then your multiple devices driver will be able to use the so-called linear mode, i.e. it will combine the disk partitions by simply appending one to the other.
See Software-RAID-HOWTO.
Example:
modprobe linear |
There are no module parameters.
This driver lets you combine several disk partitions into one logical block device.
If you use this, then your multiple devices driver will be able to use the so-called raid0 mode, i.e. it will combine the disk partitions into one logical device in such a fashion as to fill them up evenly, one chunk here and one chunk there. This will increase the throughput rate if the partitions reside on distinct disks.
See Software-RAID-HOWTO.
Example:
modprobe raid0 |
There are no module parameters.
A ramdisk is a block device whose storage is composed of system memory (real memory; not virtual). You can use it like a very fast disk device and also in circumstances where you need a device, but don't have traditional hardware devices to play with.
A common example of the latter is for a rescue system -- a system you use to diagnose and repair your real system. Since you don't want to mess with your real disks, you run off ramdisks. You might load data into these ramdisks from external media such as floppy disks.
Sometimes, you have your boot loader (e.g. lilo) create a ramdisk and load it with data (perhaps from a floppy disk). Of course, if you do this, you cannot use the LKM version of the ramdisk driver because the driver will have to be in the kernel at boot time.
A ramdisk is actually conceptually simple in Linux. Disk devices operate through memory because of the buffer cache. The only difference with a ramdisk is that you never actually get past the buffer cache to a real device. This is because with a ramdisk, 1) when you first access a particular block, Linux just assumes it is all zeroes; and 2) the device's buffer cache blocks are never written to the device, ergo never stolen for use with other devices. This means reads and writes are always to the buffer cache and never reach the device.
There is additional information about ramdisks in the file Documentation/ramdisk.txt in the Linux source tree.
Example:
modprobe rd |
There are no module parameters that you can supply to the LKM, but if you bind the module into the base kernel, there are kernel parameters you can pass to it. See BootPrompt-HOWTO.
Very old 8 bit hard disk controllers used in the IBM XT computer. No, the existence of XT disk support does NOT mean that you can run Linux on an IBM XT :).
Example:
modprobe xd |
There are no module parameters.
Detailed information about SCSI drivers is in SCSI-2.4-HOWTO.
Linux's SCSI function is implemented in three layers, and there are LKMs for all of them.
In the middle is the mid-level driver or SCSI core. This consists of the scsi_mod LKM. It does all those things that are common among SCSI devices regardless of what SCSI adapter you use and what class of device (disk, scanner, CD-ROM drive, etc.) it is.
There is a low-level driver for each kind of SCSI adapter -- typically, a different driver for each brand. For example, the low-level driver for Advansys adapters (made by the company which is now Connect.com) is named advansys. (If you are comparing ATA (aka IDE) and SCSI disk devices, this is a major difference -- ATA is simple and standard enough that one driver works with all adapters from all companies. SCSI is less standard and as a result you should have less confidence in any particular adapter being perfectly compatible with your system).
High-level drivers present to the rest of the kernel an interface appropriate to a certain class of devices. The SCSI high-level driver for tape devices, st, for example, has ioctls to rewind. The high-level SCSI driver for CD-ROM drives, sr, does not.
Note that you rarely need a high-level driver specific to a certain brand of device. At this level, there is little room for one brand to be distinguishable from another.
One SCSI high-level driver that deserves special mention is sg. This driver, called the "SCSI generic" driver, is a fairly thin layer that presents a rather raw representation of the SCSI mid-level driver to the rest of the kernel. User space programs that operate through the SCSI generic driver (because they access device special files whose major number is the one registered by sg (to wit, 21)) have a detailed understanding of SCSI protocols, whereas user space programs that operate through other SCSI high-level drivers typically don't even know what SCSI is. SCSI-Programming-HOWTO has complete documentation of the SCSI generic driver.
The layering order of the SCSI modules belies the way the LKMs depend upon each other and the order in which they must be loaded. You always load the mid-level driver first and unload it last. The low-level and high-level drivers can be loaded and unloaded in any order after that, and they hook themselves into and establish dependency on the mid-level driver at both ends. If you don't have a complete set, you will get a "device not found" error when you try to access a device.
Most SCSI low-level (adapter) drivers don't have LKM parameters; they do generally autoprobe for card settings. If your card responds to some unconventional port address you must bind the driver into the base kernel and use kernel "command line" options. See BootPrompt-HOWTO. Or you can twiddle The Source and recompile.
Many SCSI low-level drivers have documentation in the drivers/scsi directory in the Linux source tree, in files called README.*.
Example:
modprobe sd_mod |
There are no module parameters.
Example:
modprobe st |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
Example:
modprobe sr_mod |
There are no module parameters.
See the explanation of this special high-level driver above.
Example:
modprobe sg |
There are no module parameters.
Example:
modprobe wd7000 |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver atoprobes the card and requires installed BIOS.
Example:
modprobe aha154x |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver atoprobes the card and requires installed BIOS.
Example:
modprobe aha1542 |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver autoprobes the card at 0x330 and 0x334 only.
Example:
modprobe aha1740 |
There are no module parameters.
This driver autoprobes the card.
Example:
modprobe aic7xxx |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver autoprobes the card and BIOS must be enabled.
Example:
modprobe advansys asc_iopflag=1 asc_ioport=0x110,0x330 asc_dbglvl=1 |
Module Parameters:
enable port scanning
disable port scanning
I/O port addresses to scan for Advansys SCSI adapters
debugging level:
Errors only
High level tracing
Verbose tracing
If you bind this driver into the base kernel, you can pass parameters to it via the kernel boot parameters. See BootPrompt-HOWTO.
Example:
modprobe in2000 |
There are no module parameters.
This driver autoprobes the card. No BIOS is required.
The list of BusLogic cards this driver can drive is long. Read file drivers/scsi/README.BusLogic in the Linux source tree to get the total picture.
Example:
modprobe BusLogic |
There are no module parameters.
If you bind this driver into the base kernel, you can pass parameters to it via the kernel boot parameters. See BootPrompt-HOWTO.
Example:
modprobe dtc |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver autoprobes the card.
This driver handles DPT PM2011/021/012/022/122/322.
Example:
modprobe eata |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver handles DPT, NEC, AT&T, SNI, AST, Olivetti, and Alphatronix.
This driver handles DPT Smartcache, Smartcache III and SmartRAID.
Example:
modprobe eata_dma |
There are no module parameters.
Autoprobe works in all configurations.
This driver handles old DPT PM2001, PM2012A.
Example:
modprobe eata_pio |
There are no module parameters.
Example:
modprobe fdomain |
There are no module parameters.
This driver autoprobes the card and requires installed BIOS.
Example:
modprobe NCR5380 ncr_irq=xx ncr_addr=xx ncr_dma=xx ncr_5380=1 \
ncr_53c400=1 |
modprobe g_NCR5380 ncr_irq=5 ncr_addr=0x350 ncr_5380=1 |
modprobe g_NCR5380 ncr_irq=255 ncr_addr=0xc8000 ncr_53c400=1 |
Parameters:
the irq the driver is to service. 255 means no or DMA interrupt. 254 to autoprobe for an IRQ line if overridden on the command line.
the I/O port address or memory mapped I/O address, whichever is appropriate, that the driver is to drive
the DMA channel the driver is to use
1 = set up for a NCR5380 board
1 = set up for a NCR53C400 board
If you bind this driver into the base kernel, you can pass parameters to it via the kernel boot parameters. See BootPrompt-HOWTO.
Example:
modprobe NCR53c406a |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
Example:
modprobe 53c7,8xx |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver autoprobes the card and requires installed BIOS.
Example:
modprobe ncr53c8xx |
There are no module parameters.
See the file drivers/scsi/README.ppa in the Linux source tree for details.
Example:
modprobe ppa ppa_base=0x378 ppa_nybble=1 |
Parameters:
Base address of the PPA's I/O port. Default 0x378.
Delay used in data transfers, in microseconds. Default is 1.
Delay used in other operations, in microseconds. Default is 6.
1 = Use 4-bit mode. 0 = don't. Default is 0.
Example:
modprobe pas16 |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver autoprobes the card. No BIOS is required.
Example:
modprobe qlogicfas |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
Example:
modprobe qlogicisp |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
Requires firmware.
This driver is for Seagate ST-02 and Future Domain TMC-8xx.
Example:
modprobe seagate |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver autoprobes for address only. The IRQ is fixed at 5. The driver requires installed BIOS.
Example:
modprobe t128 |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver autoprobes the card. The driver requires installed BIOS.
Example:
modprobe u14-34f |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
This driver autoprobes the card, but not the 0x310 port. No BIOS is required.
Example:
modprobe ultrastor |
There are no module parameters for the LKM, but if you bind this module into the base kernel, you can pass some parameters via the Linux boot parameters. See BootPrompt-HOWTO.
Example:
modprobe bsd_comp |
There are no module parameters.
This module depends on module ppp.
This module contains routines to compress and uncompress tcp packets (for transmission over low speed serial lines).
These routines are required by PPP (also ISDN-PP) and SLIP protocols, and are used by the LKMs that implement those protocols.
Example:
modprobe slhc |
There are no module parameters.
This is said to be a bit-bucket device (i.e. traffic you send to this device is consigned into oblivion) with a configurable IP address. It is most commonly used in order to make your currently inactive SLIP address seem like a real address for local programs.
However, it also functions as a sort of loopback device. You configure it for a particular IP address and any packet you send to that IP address via this interface comes back and appears as a packet received by that interface for that IP address. This is especially handy for an IP address that would normally be reflected by another interface (a PPP interface, perhaps), but that interface is down right now.
You can have multiple dummy interfaces. They are named dummy0, dummy1, etc.
Example:
modprobe dummy |
There are no module parameters.
If you have two serial connections to some other computer (this usually requires two modems and two telephone lines) and you use PPP (a protocol for sending internet traffic over telephone lines) or SLIP (an older alternative to PPP) on them, you can make them behave like one double speed connection using this driver.
Example:
modprobe eql |
There are no module parameters.
This implements the frame relay protocol; frame relay is a fast low-cost way to connect to a remote internet access provider or to form a private wide area network. The one physical line from your box to the local "switch" (i.e. the entry point to the frame relay network) can carry several logical point-to-point connections to other computers connected to the frame relay network. To use frame relay, you need supporting hardware (FRAD) and certain programs from the net- tools package as explained in Documentation/networking/framerelay.txt in the Linux source tree.
Example:
modprobe dlci |
There are no module parameters.
This is a driver for the Sangoma S502A, S502E and S508 Frame Relay Access Devices. These are multi-protocol cards, but this driver can drive only frame relay right now. Please read Documentation/networking/framerelay.txt in the Linux source tree.
Example:
modprobe sdla |
There are no module parameters.
This module depends on module dlci.
PLIP (Parallel Line Internet Protocol) is used to create a mini network consisting of two (or, rarely, more) local machines. The parallel ports (the connectors virtually all ISA-descendant computers have that are normally used to attach printers) are connected using "null printer" or "Turbo Laplink" cables which can transmit 4 bits at a time or using special PLIP cables, to be used on bidirectional parallel ports only, which can transmit 8 bits at a time. The cables can be up to 15 meters long. This works also if one of the machines runs DOS/Windows and has some PLIP software installed, e.g. the Crynwr PLIP packet driver and winsock or NCSA's telnet.
See PLIP-Install-HOWTO.
Example:
modprobe plip io=0x378 irq=7 |
Parameters:
Port address of parallel port driver is to drive.
IRQ number of IRQ driver is to service. Default is IRQ 5 for port at 0x3bc, IRQ 7 for port at 0x378, and IRQ 9 for port at 0x278.
PPP (Point to Point Protocol) is the most common protocol to use over a serial port (with or without a modem attached) to create an IP network link between two computers.
Along with this kernel driver, you need the user space program pppd running.
See PPP-HOWTO.
Example:
modprobe ppp |
There are no module parameters.
This module depends on module slhc.
The module also accesses serial devices, which are driven by the serial module, so it depends on that module too. This dependency is not detected by depmod, so you either have to declare it manually or load serial explicitly.
SLIP (Serial Line Internet Protocol) is like PPP, only older and simpler.
Example:
modprobe slip slip_maxdev=1 |
Parameters:
Maximum number of devices the driver may use at one time. Default is 256.
This module depends on module slhc.
The module also accesses serial devices, which are driven by the serial module, so it depends on that module too. This dependency is not detected by depmod, so you either have to declare it manually or load serial explicitly.
This is a driver for Baycom style simple amateur radio modems that connect to either a serial interface or a parallel interface. The driver works with the ser12 and par96 designs.
For more information, see http://www.baycom.org/~tom.
Example:
modprobe baycom modem=1 iobase=0x3f8 irq=4 options=1 |
Parameters:
major number the driver should use; default 60
modem type of the first channel (minor 0):
ser12
par96/par97
base address of the port the driver is to drive. Common values are for ser12 0x3f8, 0x2f8, 0x3e8, 0x2e8 and for par96/par97 0x378, 0x278, 0x3bc.
IRQ the driver is to service. Common values are 3 and 4 for ser12 and 7 for for par96/par97.
use hardware DCD
use software DCD
STRIP is a radio protocol developed for the MosquitoNet project to send Internet traffic using Metricom radios. Metricom radios are small, battery powered, 100kbit/sec packet radio transceivers, about the size and weight of a wireless telephone. (You may also have heard them called "Metricom modems" but we avoid the term "modem" because it misleads many people into thinking that you can plug a Metricom modem into a phone line and use it as a modem.) You can use STRIP on any Linux machine with a serial port, although it is obviously most useful for people with laptop computers.
Example:
modprobe strip |
There are no module parameters.
WaveLAN card are for wireless ethernet-like networking. This driver drives AT&T GIS and NCR WaveLAN cards.
Example:
modprobe wavelan io=0x390 irq=0 |
Parameters:
Address of I/O port on the card. Default is 0x390. You can set a different address on the card, but it is not recommended.
IRQ the driver is to service. Default is 0. Any other value is ignored and the card still services IRQ 0.
This is a driver for the WIC parallel port radio bridge.
Example:
modprobe wic |
It appears that devices wic0, wic1 and wic2 are directly related to corresponding lpN ports.
These cards are used to connect your Linux box to an amateur radio in order to communicate with other computers. If you want to use this, read Documentation/networking/z8530drv.txt in the Linux kernel source tree and HAM-HOWTO.
Example:
modprobe scc |
There are no module parameters.
This is driver code for the 8390 Ethernet chip on which many Ethernet adapters are based. This is not a complete interface driver; the routines in this module are used by drivers for particular Ethernet adapters, such as ne and 3c503.
Example:
modprobe 8390 |
There are no module parameters.
This is a driver for the venerable NE2000 Ethernet adapter, its NE1000 forerunner, and all the generic Ethernet adapters that emulate this de facto standard card. This is an ISA bus card. For the PCI version, see the ne2k-pci module.
Example:
modprobe ne io=0x300 irq=11 |
Parameters:
Address of I/O port on the card. This parameter is mandatory, but you may specify 0x000 to have the driver autoprobe 0x300, 0x280, 0x320, 0x340, and 0x360.
IRQ the driver is to service. If you don't specify this, the driver determines it by autoIRQ probing.
The value 0xBAD means to assume the card is poorly designed in that it does not acknowledge a reset or does not have a valid 0x57,0x57 signature. If you have such a card and do not specify this option, the driver will not recognize it.
With any other value, the option has no effect.
You can repeat the options to specify additional cards. The nth occurence of an option applies to the nth card.
This module depends on module 8390.
This is a driver for the PCI version of the venerable NE2000 Ethernet adapter, and all the generic Ethernet adapters that emulate this de facto standard card.
Example:
modprobe ne io=0x300 irq=11 |
Parameters:
Level of debug messages. 0 means no messages. 1 is the default. Higher numbers mean more debugging messages.
The value of this option determines what options are set in the network adapter. Each bit of the value, expressed as a binary number, controls one option. The only option defined is full duplex, which is the 6th least significant bit. It is much easier to use the full_duplex option instead.
A "1" value sets the adapter in full duplex mode. A "0" value sets it in half duplex mode. If you include the full duplex flag in the flags you specify with the options parameter, the full_duplex has no effect.
You may repeat the options and full_duplex
parameters once per network adapter, for up to 8 network adapter.This driver can drive the following chipsets:
RealTek RTL-8029
Winbond 89C940
Winbond W89C940F
KTI ET32P2
NetVin NV5000SC
Via 86C926
SureCom NE34
Holtek HT80232
Holtek HT80229
Compex RL2000
This module depends on module 8390.
This is a driver for 3COM's 3c501 Ethernet adapter.
Example: modprobe 3c501 io=0x280 irq=5
Parameters:
Address of I/O port on the card.
IRQ the driver is to service. Default is 5.
This is a driver for 3COM's 3c503 Ethernet adapter.
Example:
modprobe 3c503 io=0x300 irq=5 xcvr=0 |
Parameters:
Address of I/O port on the card.
IRQ the driver is to service.
Determines whether to use external tranceiver.
no
yes
This module depends on module 8390.
This is a driver for 3COM's 3c505 Ethernet adapter.
Example:
modprobe 3c503 io=0x300 irq=5 xcvr=0 |
Parameters:
Address of I/O port on the card.
IRQ the driver is to service.
This module depends on module 8390.
This is a driver for 3COM's 3c507 Ethernet adapter.
Example:
modprobe 3c503 io=0x300 irq=5 xcvr=0 |
Parameters:
Address of I/O port on the card.
IRQ the driver is to service.
This module depends on module 8390.
This is a driver for 3COM's 3c507 and 3c579 Ethernet adapters.
Example:
modprobe 3c503 io=0x300 irq=5 xcvr=0 |
Parameters:
Address of I/O port on the card.
IRQ the driver is to service.
Module load-time probing Works reliably only on EISA, ISA ID-PROBE IS NOT RELIABLE! Bind this driver into the base kernel for now, if you need it auto-probing on an ISA-bus machine.
This is a driver for the following 3COM Ethernet adapters:
3c590 Vortex 10Mbps.
3c595 Vortex 100baseTX.
3c595 Vortex 100baseT4.
3c595 Vortex 100base-MII.
EISA Vortex 3c597.
Example:
modprobe 3c59x debug=1 options=0,,12 |
Parameters:
A number selecting the level of debug messages.
This is a string of options numbers separated by commas. There is one option number for each adapter that the driver drives (for the case that you have multiple Ethernet adapters in the system of types driven by this driver). The order of the option numbers is the order of the cards assigned by the PCI BIOS.
Each number represents a binary value. In that value, the lower 3 bits is the media type:
10baseT
10Mbs AUI
undefined
10base2 (BNC)
100base-TX
100base-FX
MII (not yet available)
Use default setting
The next bit (the "8" bit) is on for full duplex, off for half.
The next bit (the "16" bit) is on to enable bus-master, which is for experimental use only.
Details of the device driver implementation are at the top of the source file.
This is a driver for the Western Digital WD80*3 Ethernet adapters.
Example:
modprobe wd io=0x300 irq=5 mem=0x0D0000 mem_end=0x0D8000 |
Parameters:
Address of I/O port on the card.
IRQ the driver is to service.
Shared memory address
End of shared memory (address of next byte after it).
If you don't specify an I/O port, the driver probes 0x300, 0x280, 0x380, and 0x240.
If you don't specify an IRQ, the driver reads it from the adapter's EEPROM and with ancient cards that don't have it, the driver uses autoIRQ.
The driver depends on module 8390.
This is a driver for the Western Digital WD80*3 Ethernet adapters.
Example:
modprobe smc-ultra io=0x200 irq=5 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes 0x200, 0x220, 0x240, 0x280, 0x300, 0x340, and 0x380.
IRQ the driver is to service. Default is the value read from the adapter's EEPROM.
This driver depends on module 8390.
This is a driver for SMC's 9000 series of Ethernet cards.
Example:
modprobe smc9194 io=0x200 irq=5 ifport=0 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes 0x200, 0x220, etc. up through 0x3E0.
IRQ the driver is to service.
Type of Ethernet.
autodetect
TP
AUI (or 10base2)
The debug level is settable in the source code.
This is a driver for the AT1700 Ethernet adapter.
Example:
modprobe at1700 io=0x260 irq=5 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes 0x260, 0x280, 0x2A0, 0x240, 0x340, 0x320, 0x380, and 0x300.
IRQ the driver is to service.
Example:
modprobe e2100 io=0x300 irq=5 mem=0xd0000 xcvr=0 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes 0x300, 0x280, 0x380, and 0x220.
IRQ the card is to generate and the driver is to service. (The driver sets this value in the card).
shared memory address. Default is 0xd0000.
Don't select external transceiver
Select external transceiver
This module depends on module 8390.
This is a driver for the DEPCA, DE10x, DE200, DE201, DE202, and DE422 Ethernet adapters.
Example:
modprobe depca io=0x200 irq=7 |
Address of I/O port on the card. If you don't specify this, the adapter probes 0x300, and 0x200 on an ISA machine or 0x0c00 on an EISA machine.
IRQ the driver is to service. Default is 7.
This is a driver for the EtherWORKS 3 (DE203, D3204, and DE205) Ethernet adapters.
Example:
modprobe ewrk3 io=0x300 irq=5 |
Address of I/O port on the card. Default is 0x300.
IRQ the driver is to service. Default is 5.
On an EISA bus, this driver does EISA probing.
On an ISA bus, this driver does no autoprobing when loaded as an LKM. However, if you bind it into the base kernel, it probes addresses 0x100, 0x120, etc. up through 0x3C0 except 0x1E0 and 0x320.
This is a driver for the EtherExpress 16 Ethernet adapter.
Example:
modprobe eexpress io=0x300 irq=5 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes 0x300, 0x270, 0x320, and 0x340. 1
IRQ the driver is to service. The default is the value read from the adapter's EEPROM.
This is a driver for the EtherExpressPro Ethernet adapter.
Example:
modprobe eepro io=0x200 irq=5 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes 0x200, 0x240, 0x280, 0x2C0, 0x300, 0x320, 0x340, and 0x360.
IRQ the driver is to service.
This is a driver for the Fujitsu FMV-181, FMV-182, FMV-183, FMV-183, and FMV-184 Ethernet adapters.
Example:
modprobe fmv18x io=0x220 irq=5 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes 0x220, 0x240, 0x260, 0x280, 0x2a0, 0x2c0, 0x300, and 0x340.
IRQ the driver is to service.
This is a driver for HP's PCLAN+ (27247B and 27252A) Ethernet adapters.
Example:
modprobe hp-plus io=0x200 irq=5 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes 0x200, 0x240, 0x280, 0x2C0, 0x300, 0x320, and 0x340.
IRQ the driver is to service. The default is the value the driver reads from the adapter's configuration register.
This module depends on module 8390.
This is a driver for HP's PCLAN (27245 and other 27xxx series) Ethernet adapters.
Example:
modprobe hp io=0x300 irq=5 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes 0x300, 0x320, 0x340, 0x280, 0x2C0, 0x200, and 0x240.
IRQ the driver is to service. If you don't specify this, the driver determines it by autoIRQ probing.
This module depends on module 8390.
This is a driver for HP's 10/100VG PCLAN Ethernet adapters. It works with the ISA, EISA, and PCI versions.
Example:
modprobe hp100 hp100_port=0x100 |
Parameters:
Base address of I/O ports on the card. If you don't specify this, the driver autoprobes 0x100, 0x120, etc. up through 0x3E0 on an ISA bus. It does EISA probing on an EISA bus.
This is a driver for ICL's EtherTeam 16i (eth16i) and 32i (eth32i) Ethernet adapters.
Example:
modprobe eth16i io=0x2a0 irq=5 |
Parameters:
Address of I/O port on the card. If you don't specify this, the adapter probes the following adddresses. For the eth16i adapter: 0x260, 0x280, 0x2A0, 0x340, 0x320, 0x380, and 0x300. For the eth32i: 0x1000, 0x2000, 0x3000, 0x4000, 0x5000, 0x6000, 0x7000, 0x8000, 0x9000, 0xA000, 0xB000, 0xC000, 0xD000, 0xE000, and 0xF000.
IRQ the driver is to service. If you don't specify this, the driver determines it by autoIRQ probing.
This is a driver for the NI5210 Ethernet adapter.
Example:
modprobe ni52 io=0x360 irq=9 memstart=0xd0000 memend=0xd4000 |
This is a driver for the Ansel Communications EISA 3200 Ethernet adapter.
Example:
modprobe ac3200 |
This module depends on module 8390.
Example:
modprobe apricot io=0x300 irq=10 |
Parameters:
address of base I/O port on card.
IRQ that driver is to service.
This is a driver for the DE425, DE434, DE435, DE450, and DE500 Ethernet adapters.
Example:
modprobe de4x5 io=0x000b irq=10 is_not_dec=0 |
Parameters:
address of base I/O port.
IRQ the driver is to service.
For a non-DEC card using the DEC 21040, 21041, or 21140 chip, set this to 1.
Example:
modprobe tulip |
Read Documentation/networking/tulip.txt in the Linux source tree.
This is a driver for the Digi International RightSwitch SE-X EISA and PCI boards. These boards have a 4 (EISA) or 6 (PCI) port Ethernet switch and a NIC combined into a single board.
There is a tool for setting up input and output packet filters on each port, called dgrsfilt.
The management tool lets you watch the performance graphically, as well as set the SNMP agent IP and IPX addresses, IEEE Spanning Tree, and Aging time. These can also be set from the command line when the driver is loaded.
There is also a companion management tool, called xrightswitch.
Examples:
modprobe dgrs debug=1 dma=0 spantree=0 hashexpire=300 ipaddr=199,86,8,221 modprobe ipxnet=111 |
Parameters:
Level of debugging messages to print
Disable DMA on PCI card
Enable DMA on PCI card
Disable IEEE spanning tree
Enable IEEE spanning tree
Change address aging time, in seconds. Defaults is 300.
SNMP agent IP address. Value is IP address in dotted decimal notation, except with commas instead of periods.
SNMP agent IPX network number
This is a driver for the D-Link DE600 pocket Ethernet adapter.
Example:
modprobe de600 de600_debug=0 |
Parameters:
The driver expects the adapter to be at port 0x378 and generate IRQ 7. This is the same as the DOS lpt1 device. These are compile time options.
This is a driver for the D-Link DE620 pocket Ethernet adapter.
Example:
modprobe de620 bnc=0 utp=0 io=0x378 irq=7 |
Parameters:
Network is 10Base2
Network is not 10Base2
Network is 10BaseT
Network is not 10BaseT
I/O port address of port driver is to drive. Default is 0x378.
IRQ driver is to service. Default is 7.
You can't specify both bnc=1 and utp=1.
Example:
modprobe ibmtr io=0xa20 irq=5 |
Parameters:
I/O port address of port driver is to drive. Default is 0xa20.
IRQ driver is to service. By default, the driver determines the IRQ by autoIRQ probing.
Read The Fine Information in Documentation/networking/arcnet.txt in the Linux source tree. Also Arcnet hardware information arcnet-hardware.txt is found in same place.
Example:
modprobe arcnet io=0x300 irq=2 shmem=0xd0000 device=arc1 |
Parameters:
I/O port address of port driver is to drive. If you don't specify this, the driver probes addresses 0x300, 0x2E0, 0x2F0, 0x2D0, 0x200, 0x210, 0x220, 0x230, 0x240, 0x250, 0x260, 0x270, 0x280, 0x290, 0x2A0, 0x2B0, 0x2C0, 0x310, 0x320, 0x330, 0x340, 0x350, 0x360, 0x370, 0x380, 0x390, 0x3A0, 0x3E0, and 0x3F0.
IRQ driver is to service. By default, the driver determines the IRQ by autoIRQ probing.
device name.
This module provides ISDN functions used by ISDN adapter drivers.
Setting up ISDN networking is a complicated task. Read documentation found in Documentation/isdn in the Linux source tree.
Example:
modprobe isdn |
There are no module parameters.
This module depends on module slhc.
This is a driver for the ICN 2B and ICN 4B ISDN adapters.
Example:
modprobe icn portbase=0x320 membase=0xd0000 icn_id=idstring icn_id2=idstring2 |
Parameters:
Address of the base I/O port on the adapter. Defaults is 0x320.
Address of shared memory. Default is 0xd0000.
idstring for the first adapter. Must start with a character! This parameter is required.
idstring for the second adapter. Must start with a character! This parameter is required with the double card.
This module depends on module isdn.
This is a driver for the PCBIT-D ISDN adapter driver.
Example:
modprobe pcbit mem=0xd0000 irq=5 |
Parameters:
Shared memory address. Default is 0xd0000
IRQ the driver is to service. Default is 5.
This module depend on module isdn.
This is a driver for the Teles/NICCY1016PC/Creatix ISDN adapter. It can drive up to 16 cards.
Example:
modprobe teles io=0xd0000,15,0xd80,2 teles_id=idstring |
Parameters:
This is a whole collection of parameters in one. It's syntax is io=card1options [,card2options ,...] where card1options is a set of options for the first card, etc.
The syntax of card1options, etc. is sharedmem, irq, portbase, dprotocol
Address of shared memory. Default 0xd0000
IRQ driver is to service.
Address of base I/O port.
D-channel protocol of the card
1TR6
EDSS1. This is the default.
Driver ID for accessing with utilities and identification when using a line monitor. Value must start with a character! Default: none.
The driver determines the type of card from the port, irq and shared memory address:
port == 0, shared memory != 0 -> Teles S0-8
port != 0, shared memory != 0 -> Teles S0-16.0
port != 0, shared memory == 0 -> Teles S0-16.3
This module depends on module isdn.
This is a driver for the Aztech, Orchid, Okano, Wearnes, TXC, and CDROM devices (which have special non-SCSI non-ATA interfaces).
Example:
modprobe aztcd aztcd=0x340 |
Parameters:
address of base I/O port
Read Documentation/cdrom/aztcd in the Linux source tree for full information.
This is a driver for the Goldstar R420 CDROM drive, which does not use either an ATA or SCSI interface.
Example:
modprobe gscd gscd=0x340 |
Parameters:
address of base I/O port. Default is 0x340, which will work for most applications. You select the address of the drive with the PN801-1 through PN801-4 jumpers on the Goldstar Interface Card. Appropriate settings are: 0x300, 0x310, 0x320, 0x330, 0x340, 0x350, 0x360, 0x370, 0x380, 0x390, 0x3A0, 0x3B0, 0x3C0, 0x3D0, 0x3E0, and 0x3F0.
This is a driver for the Matsushita, Panasonic, Creative, Longshine, and TEAC CDROM drives that don't attach via ATA or SCSI.
Example:
modprobe sbpcd sbpcd=0x340 |
Parameters:
address of base I/O port
An additional parameter is an SBPRO setting, as described in Documentation/cdrom/sbpcd in the Linux source tree.
This is a driver for Mitsumi CDROM drives that don't attach via ATA or SCSI. It does not handle XA or multisession.
Example:
modprobe mcd mcd=0x300,11,0x304,5 |
Parameters:
This is a comma separated list of i/o base addresses and IRQs, in pairs.
This driver is like mcd, only it has XA and multisession functions.
Example:
modprobe mcdx mcdx=0x300,11,0x304,5 |
This is the driver for the so-called "dolphin" CDROM drive form Optics Storage, with the 34-pin Sony-compatible interface. For the ATA-compatible Optics Storage 8001 drive, you will want the ATAPI CDROM driver. The driver also seems to work with the Lasermate CR328A.
Example:
modprobe optcd optcd=0x340 |
Parameters:
address of base I/O port
This is the driver for the Philips/LMS cm206 CDROM drive in combination with the cm260 host adapter card.
Example:
modprobe cm206 cm206=0x300,11 |
Parameters:
The address of the base I/O port the driver is to drive and the IRQ the driver is to service, separated by a comma. It doesn't matter what order you put them in, and you may specify just one, in which case the other defaults.
Example:
modprobe sjcd sjcd_base=0x340 |
Parameters:
address of the base I/O port the driver is to drive. Default is 0x340.
The driver uses no IRQ and no DMA channel.
This is a driver for the ISP16 or MAD16 or Mozart soft configurable cdrom interface.
Example:
modprobe isp16 isp16_cdrom_base=0x340 isp16_cdrom_irq=3
isp16_cdrom_dma=0 isp16_cdrom_type=Sanyo |
Parameters:
address of base I/O port the driver is to drive. Valid values are 0x340, 0x320, 0x330, and 0x360.
IRQ the driver is to service. Valid values are 0, 3, 5, 7, 9, 10, and 11.
DMA channel the driver is to use with the device. Valid values are 0, 3, 5, 6, and 7.
Type of device being driven. Valid values are noisp16, Sanyo, Panasonic, Sony and Mitsumi. Note that these values are case sensitive.
Example:
modprobe cdu31a cdu31a_port=0x340 cdu31a_irq=5 |
Parameters:
address of base I/O port the driver is to drive. This parameter is mandatory.
IRQ the driver is to service. If you don't specify this, the driver does not use interrupts.
Example:
modprobe sonycd535 sonycd535=0x340 |
Parameters:
address of the base I/O port the driver is to drive.
Example:
modprobe ext2 |
There are no module parameters.
This module provides services for use by the MSDOS and VFAT filesystem drivers.
Example:
modprobe fat |
There are no module parameters.
Example:
modprobe msdos |
There are no module parameters.
This module depends on the module fat.
Example:
modprobe vfat |
There are no module parameters.
This module depends on module fat.
This is a driver for the UMSDOS filesystem type, which is a unix style filesystem built on top of an MSDOS FAT filesystem.
Example:
modprobe vfat |
There are no module parameters.
This module depends on the fat and msdos modules.
SMBFS is a filesystem type which has an SMB protocol interface. This is the protocol Windows for Workgroups, Windows NT or Lan Manager use to talk to each other. SMBFS was inspired by Samba, the program written by Andrew Tridgell that turns any unix host into a file server for DOS or Windows clients. See ftp://nimbus.anu.edu.au/pub/tridge/samba/ for this interesting program suite and lots of more information on SMB and NetBIOS over TCP/IP. There you also find explanation for concepts like netbios name or share.
To use SMBFS, you need a special mount program, which can be found in the ksmbfs package, found on ftp://ibiblio.org/pub/Linux/system/Filesystems/smbfs.
Example:
modprobe smbfs |
There are no module parameters
NCPFS is a filesystem type which has an NCP protocol interface, designed by the Novell Corporation for their NetWare product. NCP is functionally similar to the NFS used in the TCP/IP community. To mount a Netware filesystem, you need a special mount program, which can be found in the ncpfs package. Homesite for ncpfs is ftp.gwdg.de/pub/linux/misc/ncpfs, but Ibiblio and its many mirrors will have it as well.
Related products are Linware and Mars_nwe, which will give Linux partial NetWare Server functionality.
Mars_nwe can be found on ftp.gwdg.de/pub/linux/misc/ncpfs.
Example:
modprobe ncpfs |
There are no module parameters.
This module depends on module ipx.
Example:
modprobe isofs |
There are no module parameters.
This filesystem driver for OS/2's HPFS filesystem provides only read-only access.
Example:
modprobe hpfs |
There are no module parameters.
This is the implementation of the SystemV/Coherent filesystem type for Linux.
It implements all of
Xenix FS
SystemV/386 FS
Coherent FS
Example:
modprobe sysv |
There are no module parameters.
Apparently for mounting disks with FreeBSD and/or Sun partitions. No documentation exists, apart from The Source.
This filesystem driver provides only read-only access.
Example:
modprobe ufs |
There are no module parameters.
A whole bunch of device types that don't appear in large enough numbers on a system to deserve major numbers of their own share Major Number 10 and are collectively called "miscellaneous" character devices. This module provides the common interface to serve that major number, but there are individual drivers for the specific device types. Those drivers register themselves with this driver.
Example:
modprobe misc |
There are no module parameters.
This driver drives conventional serial ports (UARTs), but not some of the specialized high performance multi-port devices.
NOTE: serial is required by other modules, such as ppp and slip. Also it is required by serial mice and accordingly by gpm. However this isn't the regular kind of dependency that is detected by module handling tools, so you must load serial manually.
Example:
modprobe serial |
There are no module parameters.
Example:
modprobe cyclades |
There are no module parameters.
The intelligent boards also need to have their firmware code downloaded to them. This is done via a user level application supplied in the driver package called stlload. Compile this program where ever you dropped the package files, by typing make. In its simplest form you can then type stlload in this directory and that will download firmware into board 0 (assuming board 0 is an EasyConnection 8/64 board). To download to an ONboard, Brumby or Stallion do:
Read the information in the file Documentation/stallion.txt in the Linux source tree.
The intelligent boards also need to have their firmware code downloaded to them. This is done via a user level application supplied in the driver package called stlload.
Read the information in the file Documentation/stallion.txt in the Linux source tree.
Example:
modprobe stallion |
There are no module parameters.
The intelligent boards also need to have their firmware code downloaded to them. This is done via a user level application supplied in the driver package called stlload.
Read the information at /usr/src/linux/drivers/char/README.stallion.
Example:
modprobe istallion |
There are no module parameters.
Example:
modprobe riscom8 iobase=0xXXX iobase1=0xXXX iobase2=... |
This driver can drive up to 4 boards at time.
Example:
modprobe lp.o io=0x378 irq=0 |
This driver probes ports 0x278, 0x378, and 0x3bc.
Note: loading lp without any parameters will grab all parallel ports.
Example:
modprobe atixlmouse |
There are no parameters.
This module depends on module misc.
Example:
modprobe busmouse |
There are no module parameters.
This module depends on module misc.
Example:
modprobe msbusmouse |
There are no module parameters.
This module depends on module misc.
Example:
modprobe psaux |
There are no module parameters.
This module depends on module misc.
For SCSI tape device drivers, see Section 13.3. There are no LKMs for QIC-02 tape devices, but there is a device driver you can bind into the base kernel.
Example:
modprobe ftape tracing=3 |
Optional parameter tracing can take following values
bugs
+ errors
+ warnings
+ information
+ more information
+ program flow
+ fdc/dma info
+ data flow
+ everything else
The default is 3.
Example:
modprobe wdt |
There are no module parameters.
The device address is hardcoded as 0x240. The IRQ is hardcoded as 14.
This module depends on module misc.
Example:
modprobe softdog |
There are no module parameters.
This module depends on module misc.
Example:
modprobe pcwd |
There are no module parameters.
This module depends on module misc.
Configuring sound is a complex task. Read the files in directory Documention/sound in the Linux source tree.
Example:
modprobe sound |
Option: dma_buffsize=32768
This HOWTO is enthusiastically maintained by Bryan Henderson <bryanh@giraffe-data.com>. If you find something incorrect or incomplete or can't understand something, Bryan wants to know so maybe the next reader can be saved the trouble you had.
The source for this document is DocBook SGML, and is available from the Linux Documentation Project.
I have derived this (in 2001) from the HOWTO of the same name by Laurie Tischler, dated 1997. While I have kept all of the information from that original document (where it is still useful), I have rewritten the presentation entirely and have added a lot of other information. The original HOWTO's primary purpose was to document LKM parameters.
The original HOWTO was first released (Release 1.0) June 20, 1996, with a second release (1.1) October 20, 1996.
The first release of Bryan's rewrite was in June 2001.
Here is Lauri Tischler's copyright notice from the original document from which this is derived:
This document is Copyright 1996© by Lauri Tischler. Permisson is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this document under the conditions for verbatim copying, provided that this copyright notice is included exactly as in the original, and that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this document into another language, under the above conditions for modified versions.
Bryan Henderson, the current maintainer and contributing author of this document, licenses it under the same terms as above. His work is Copyright 2001©.
| [1] | For the pedantic, see Section 10.6. |
| [2] | You probably know this type of disk as "IDE". Strictly speaking, IDE is an incorrect appelation. IDE refers to the "Integrated Drive Electronics" which all modern disk drives, notably all SCSI disk drives, use. The first IDE drives in common usage were ATA, and the names kind of got confused. ATA, like SCSI, is a precise specification of electrical signals, commands, etc. |