Which modules linux

You didnt find this module. When you are looking for linux drivers. You should know which linux modules are loaded or modulars or during compiling kernel didnt enable i2c-dev module. Add a comment. Active Oldest Votes. Improve this answer. Redhat 7 modules files are compressed in. Pozinux Discovered the same thing here on Arch linux at 4. GAD3R Martin Hansen Martin Hansen 2 2 silver badges 3 3 bronze badges.

Requires necessary completion scripts in order to work — smac Where it's important to highlight that lsmod only shows already loaded modules. The Author of this thread had the problem to load a module that wasn't in the map of the loadable kernel modules. Besides, this solution only applies to archlinux.

Which might be not the distribution of the Author and might not solve the problem for others. Functions so marked are generally a low-level component of the interface and should be used with caution. Kernel code cannot do floating point arithmetic. Given that there really is no need for floating point in kernel code, the extra overhead is not worthwhile.

There is, of course, a lot more to that whole process than we have seen so far. This section provides more detail on how a module author turns source code into an executing subsystem within the kernel. As the first step, we need to look a bit at how modules must be built. The build process for modules differs significantly from that used for user-space applications; the kernel is a large, standalone program with detailed and explicit requirements on how its pieces are put together.

The build process also differs from how things were done with previous versions of the kernel; the new build system is simpler to use and produces more correct results, but it looks very different from what came before. The kernel build system is a complex beast, and we just look at a tiny piece of it. There are some prerequisites that you must get out of the way before you can build kernel modules. The first is to ensure that you have sufficiently current versions of the compiler, module utilities, and other necessary tools.

Trying to build a kernel and its modules with the wrong tool versions can lead to no end of subtle, difficult problems. Note that, occasionally, a version of the compiler that is too new can be just as problematic as one that is too old; the kernel source makes a great many assumptions about the compiler, and new releases can sometimes break things for a while.

If you still do not have a kernel tree handy, or have not yet configured and built that kernel, now is the time to go do it. You cannot build loadable modules for a 2. It is also helpful though not required to be actually running the kernel that you are building for. Once you have everything set up, creating a makefile for your module is straightforward. Readers who are familiar with make , but not with the 2. The above line is not how a traditional makefile looks, after all.

The answer, of course, is that the kernel build system handles the rest. The assignment above which takes advantage of the extended syntax provided by GNU make states that there is one module to be built from the object file hello.

The resulting module is named hello. If, instead, you have a module called module. For a makefile like those shown above to work, it must be invoked within the context of the larger kernel build system. This command starts by changing its directory to the one provided with the -C option that is, your kernel source directory.

Typing the previous make command can get tiresome after a while, so the kernel developers have developed a sort of makefile idiom, which makes life easier for those building modules outside of the kernel tree. The trick is to write your makefile as follows:.

Once again, we are seeing the extended GNU make syntax in action. This makefile is read twice on a typical build. It locates the kernel source directory by taking advantage of the fact that the symbolic link build in the installed modules directory points back at the kernel build tree. On the second reading, the makefile sets obj-m , and the kernel makefiles take care of actually building the module. This mechanism for building modules may strike you as a bit unwieldy and obscure.

Once you get used to it, however, you will likely appreciate the capabilities that have been programmed into the kernel build system. Do note that the above is not a complete makefile; a real makefile includes the usual sort of targets for cleaning up unneeded files, installing modules, etc.

See the makefiles in the example source directory for a complete example. After the module is built, the next step is loading it into the kernel. The program loads the module code and data into the kernel, which, in turn, performs a function similar to that of ld , in that it links any unresolved symbol in the module to the symbol table of the kernel.

Thus, if a module is correctly designed, it can be configured at load time; load-time configuration gives the user more flexibility than compile-time configuration, which is still used sometimes. Load-time configuration is explained in Section 2.

The modprobe utility is worth a quick mention. It differs in that it will look at the module to be loaded to see whether it references any symbols that are not currently defined in the kernel. If any such references are found, modprobe looks for other modules in the current module search path that define the relevant symbols. When modprobe finds those modules which are needed by the module being loaded , it loads them into the kernel as well.

As mentioned before, modules may be removed from the kernel with the rmmod utility. Note that module removal fails if the kernel believes that the module is still in use e. If you reach a point where you are considering using this option, however, things are likely to have gone wrong badly enough that a reboot may well be the better course of action. The lsmod program produces a list of the modules currently loaded in the kernel.

Some other information, such as any other modules making use of a specific module, is also provided. Modules are strongly tied to the data structures and function prototypes defined in a particular kernel version; the interface seen by a module can change significantly from one kernel version to the next.

This is especially true of development kernels, of course. The kernel does not just assume that a given module has been built against the proper kernel version. One of the steps in the build process is to link your module against a file called vermagic. When an attempt is made to load a module, this information can be tested for compatibility with the running kernel. If you need to compile a module for a specific kernel version, you will need to use the build system and source tree for that particular version.

Kernel interfaces often change between releases. If you are writing a module that is intended to work with multiple versions of the kernel especially if it must work across major releases , you likely have to make use of macros and ifdef constructs to make your code build properly. This edition of this book only concerns itself with one major version of the kernel, so you do not often see version tests in our example code. But the need for them does occasionally arise.

This macro expands to a string describing the version of this kernel tree. For example, " 2. This macro expands to the binary representation of the kernel version, one byte for each part of the version release number. For example, the code for 2. This is the macro used to build an integer version code from the individual numbers that build up a version number. This macro is very useful when you need to compare the current version and a known checkpoint. Version dependency should, however, not clutter driver code with hairy ifdef conditionals; the best way to deal with incompatibilities is by confining them to a specific header file.

As a general rule, code which is explicitly version or platform dependent should be hidden behind a low-level macro or function. High-level code can then just call those functions without concern for the low-level details. Code written in this way tends to be easier to read and more robust. Each computer platform has its peculiarities, and kernel designers are free to exploit all the peculiarities to achieve better performance in the target object file. Unlike application developers, who must link their code with precompiled libraries and stick to conventions on parameter passing, kernel developers can dedicate some processor registers to specific roles, and they have done so.

Moreover, kernel code can be optimized for a specific processor in a CPU family to get the best from the target platform: unlike applications that are often distributed in binary format, a custom compilation of the kernel can be optimized for a specific computer set. For example, the IA32 x86 architecture has been subdivided into several different processor types. The old processor is still supported for now , even though its instruction set is, by modern standards, quite limited.

The more modern processors in this architecture have introduced a number of new capabilities, including faster instructions for entering the kernel, interprocessor locking, copying data, etc. Newer processors can also, when operated in the correct mode, employ bit or larger physical addresses, allowing them to address more than 4 GB of physical memory. Other processor families have seen similar improvements.

The kernel, depending on various configuration options, can be built to make use of these additional features. Clearly, if a module is to work with a given kernel, it must be built with the same understanding of the target processor as that kernel was.

Once again, the vermagic. When a module is loaded, the kernel checks the processor-specific configuration options for the module and makes sure they match the running kernel. If the module was compiled with different options, it is not loaded. If you are planning to write a driver for general distribution, you may well be wondering just how you can possibly support all these different variations. The best answer, of course, is to release your driver under a GPL-compatible license and contribute it to the mainline kernel.

Some vendors have released tools to make this task easier. If you must distribute your driver in binary form, you need to look at the different kernels provided by your target distributions, and provide a version of the module for each.

Be sure to take into account any errata kernels that may have been released since the distribution was produced. Then, there are licensing issues to be considered, as we discussed in Section 1. As a general rule, distributing things in source form is an easier way to make your way in the world. Use Them. Sometimes, the Module file name will imply about the type of Hardware it supports. At the command-line, you can use pydoc modules. How would you display a list of all loaded modules in the current kernel?

At Stanford, we have a system that uses the module command to load different programs as you are describing. Basically, the module command modifies your environment so that the path and other variables are set so that you can use a program such as gcc, matlab, or mathematica. This could be useful if, for example, the associated hardware is not needed, or if loading that module causes problems: for instance there may be two kernel modules that try to control the same piece of hardware, and loading them together would result in a conflict.

Some modules are loaded as part of the initramfs. Running mkinitcpio -v will list all modules pulled in by the various hooks e. Remember to add that.

Create a. If for example you want to prevent the pcspkr module from loading:. However, there is a workaround for this behaviour; the install command instructs modprobe to run a custom command instead of inserting the module in the kernel as normal, so you can force the module to always fail loading with:.

A module will not be loaded if the "vermagic" string contained within the kernel module does not match the value of the currently running kernel. If it is known that the module is compatible with the current running kernel the "vermagic" check can be ignored with modprobe --force-vermagic. Related articles Boot debugging Kernels Kernel parameters Compile kernel module. Check manually if this path exists when modprobe failed to determine if this is the case.

Note: If any of the affected modules is loaded from the initramfs, then you will need to add the appropriate.