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<!DOCTYPE html><html><head><meta name="viewport" content="width=device-width"/><meta charSet="utf-8"/><title>Linux drivers</title><script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script><script id="MathJax-script" async="" src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script><script type="text/x-mathjax-config">
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</script><meta name="next-head-count" content="6"/><link rel="preload" href="/wiki/_next/static/css/52fc2ba29703df73922c.css" as="style"/><link rel="stylesheet" href="/wiki/_next/static/css/52fc2ba29703df73922c.css" data-n-g=""/><noscript data-n-css=""></noscript><link rel="preload" href="/wiki/_next/static/chunks/main-ae4733327bd95c4ac325.js" as="script"/><link rel="preload" href="/wiki/_next/static/chunks/webpack-50bee04d1dc61f8adf5b.js" as="script"/><link rel="preload" href="/wiki/_next/static/chunks/framework.9d524150d48315f49e80.js" as="script"/><link rel="preload" href="/wiki/_next/static/chunks/commons.0e1c3f9aa780c2dfe9f0.js" as="script"/><link rel="preload" href="/wiki/_next/static/chunks/pages/_app-8e3d0c58a60ec788aa69.js" as="script"/><link rel="preload" href="/wiki/_next/static/chunks/940643274e605e7596ecea1f2ff8d83317a3fb76.4841a16762f602a59f00.js" as="script"/><link rel="preload" href="/wiki/_next/static/chunks/pages/%5B%5B...slug%5D%5D-1aa198f87ede1cd0e1dc.js" as="script"/></head><body><div id="__next"><main><h1>Linux drivers</h1><section class="post-metadata"><span>Date: <!-- -->2020-09-09 05:27:17 +08:00</span><span>Date modified: <!-- -->2021-05-04 20:51:26 +08:00</span></section><nav class="toc"><ol class="toc-level toc-level-1"></ol></nav><p>Linux drivers (also called as kernel modules) are software executed in the kernel.
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Usually, they are used to communicate between hardware and create an inteface with it, making them usable.
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Examples include <a href="http://linuxwacom.sourceforge.net/">the Linux Wacom project</a> to make Wacom graphics tablet usable in Linux, those sort of stuff.
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</p><p><a href="https://www.youtube.com/watch?v=juGNPLdjLH4">Liveoverflow's video summary</a>:
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</p><ul><li><p>A driver is just a compiled module (e.g., <code class="inline-code">driver.o</code>) that makes use of the code in the Linux header and does the communication from the associated device.
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</p></li><li><p>Each driver may have functions attached to an event (e.g., opening in <code class="inline-code">module_open</code>, closing in <code class="inline-code">module_exit</code>).
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</p></li><li><p>You can insert a driver with the <code class="inline-code">insmod</code> program and remove it with the <code class="inline-code">rmmod</code> program.
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</p></li><li><p>Each driver will appear on a special filesystem in <code class="inline-code">/dev</code> as a special type of file which you can view what type of file it is with <code class="inline-code">ls -l</code>.
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</p></li><li><p>You can print out events (i.e., <code class="inline-code">printk</code>) and view it in the system log (e.g., <code class="inline-code">/var/log/syslog</code>).
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</p></li><li><p>Essentially, a driver is basically a handler that does its magic whenever an associated system call (syscall) has been invoked by the kernel.
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The kernel provides an abstraction for the events associated with the syscall.
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For example, whenever the kernel invokes a syscall for writing in the device file, the associated code defined in <code class="inline-code">module_write</code> (or something equivalent) event will run.
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</p></li><li><p>NEEDS INVESTIGATION: Another interesting of note here is how the kernel does not immediately writes the bytes in the device file until closing it.
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</p></li><li><p><a href="https://everything-is-sheep.herokuapp.com/posts/on-developing-a-linux-driver=-">An overview from a student without prior experience</a></p></li><li><p><a href="https://unix.stackexchange.com/questions/507687/graphic-tablet-veikk-pressure-sensitivity-on-linux">Creating a driver for a graphics tablet</a> on Unix StackExchange
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</p></li><li><p><a href="https://lwn.net/Kernel/LDD3/">The de-facto reference on creating Linux drivers</a></p></li><li><p><a href="https://www.youtube.com/watch?v=juGNPLdjLH4">How do Linux kernel drivers work?</a> from LiveOverflow
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</p></li><li><p><a href="https://www.youtube.com/watch?v=RyY01fRyGhM">Writing Linux kernel modules in safe Rust</a> from the Linux Foundation
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</p></li><li><p><a href="https://lwn.net/Kernel/LDD3/">Linux device drivers, 3rd edition</a>, the de-facto reference for kernel modules
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</p></li></ul><section><h2>Backlinks</h2><ul><li><a href="/wiki/linux.network-configuration">Network configuration in Linux</a></li></ul></section></main></div><script id="__NEXT_DATA__" type="application/json">{"props":{"pageProps":{"metadata":{"date":"\"2020-09-09 05:27:17 +08:00\"","date_modified":"\"2021-05-04 20:51:26 +08:00\"","language":"en","source":""},"title":"Linux drivers","hast":{"type":"root","children":[{"type":"element","tagName":"nav","properties":{"className":"toc"},"children":[{"type":"element","tagName":"ol","properties":{"className":"toc-level toc-level-1"},"children":[]}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Linux drivers (also called as kernel modules) are software executed in the kernel.\nUsually, they are used to communicate between hardware and create an inteface with it, making them usable.\nExamples include "},{"type":"element","tagName":"a","properties":{"href":"http://linuxwacom.sourceforge.net/"},"children":[{"type":"text","value":"the Linux Wacom project"}]},{"type":"text","value":" to make Wacom graphics tablet usable in Linux, those sort of stuff.\n"}]},{"type":"element","tagName":"p","properties":{},"children":[{"type":"element","tagName":"a","properties":{"href":"https://www.youtube.com/watch?v=juGNPLdjLH4"},"children":[{"type":"text","value":"Liveoverflow's video summary"}]},{"type":"text","value":":\n"}]},{"type":"element","tagName":"ul","properties":{},"children":[{"type":"element","tagName":"li","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"A driver is just a compiled module (e.g., "},{"type":"element","tagName":"code","properties":{"className":["inline-code"]},"children":[{"type":"text","value":"driver.o"}]},{"type":"text","value":") that makes use of the code in the Linux header and does the communication from the associated device.\n"}]}]},{"type":"element","tagName":"li","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Each driver may have functions attached to an event (e.g., opening in "},{"type":"element","tagName":"code","properties":{"className":["inline-code"]},"children":[{"type":"text","value":"module_open"}]},{"type":"text","value":", closing in "},{"type":"element","tagName":"code","properties":{"className":["inline-code"]},"children":[{"type":"text","value":"module_exit"}]},{"type":"text","value":").\n"}]}]},{"type":"element","tagName":"li","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"You can insert a driver with the "},{"type":"element","tagName":"code","properties":{"className":["inline-code"]},"children":[{"type":"text","value":"insmod"}]},{"type":"text","value":" program and remove it with the "},{"type":"element","tagName":"code","properties":{"className":["inline-code"]},"children":[{"type":"text","value":"rmmod"}]},{"type":"text","value":" program.\n"}]}]},{"type":"element","tagName":"li","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"Each driver will appear on a special filesystem in "},{"type":"element","tagName":"code","properties":{"className":["inline-code"]},"children":[{"type":"text","value":"/dev"}]},{"type":"text","value":" as a special type of file which you can view what type of file it is with "},{"type":"element","tagName":"code","properties":{"className":["inline-code"]},"children":[{"type":"text","value":"ls -l"}]},{"type":"text","value":".\n"}]}]},{"type":"element","tagName":"li","properties":{},"children":[{"type":"element","tagName":"p","properties":{},"children":[{"type":"text","value":"You can print out events (i.e., "},{"type":"element","tagName":"code","properties":{"className":["inline-code"]},"children":[{"type":"text","value":"printk"}]},{"type":"text","value":") and view it in the system log (e.g., "},{"type":"element","tagName":"code","properties":{"className":["inline-code"]},"children":[{"type":"text","value":"/var/log/syslog"}
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