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65 lines
3.2 KiB
Markdown
65 lines
3.2 KiB
Markdown
# About udev
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udev is a device manager for the Linux kernel that gives the system access to various running hardware via device `.rules` files also known as `udev rules`.
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udev rules are used to allow and manage the access to a specific devices, so without a proper udev rule some devices such as custom controller could not be used by RetroDECK nor by Steam or any other part of the system.
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Read more on:
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- [Debian Wiki](https://wiki.debian.org/udev)
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- [Arch Wiki](https://wiki.archlinux.org/title/udev)
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- [Wikipedia](https://en.wikipedia.org/wiki/Udev)
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## Important directories
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`/lib/udev/rules.d/`<br>
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This directory contains the default `.rules file` shipped by your system. They should generally not be edited.
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`/etc/udev/rules.d/` or `/run/udev/rules.d` (depending on the system) <br>
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This directory contains custom `.rules file` additions to those shipped in `/lib/udev/rules.d/` and the administrator can add more rules into this directory.
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If a `.rules file` exist for the same device under `/lib/udev/rules.d/` and `/etc/udev/rules.d/` the `/etc` version will always take preset over the `lib` version.
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## Example of a .rules file
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The content of a Merlin UTMS modem .rules file.
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```
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ATTRS{prod_id2}=="Merlin UMTS Modem", ATTRS{prod_id1}=="Novatel Wireless", SYMLINK+="MerlinUMTS"
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```
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A .rules file can also contain more the one devices example multiple 8Bitdo controllers:
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```
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# 8Bitdo F30 P1
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SUBSYSTEM=="input", ATTRS{name}=="8Bitdo FC30 GamePad", ENV{ID_INPUT_JOYSTICK}="1", TAG+="uaccess"
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# 8Bitdo F30 P2
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SUBSYSTEM=="input", ATTRS{name}=="8Bitdo FC30 II", ENV{ID_INPUT_JOYSTICK}="1", TAG+="uaccess"
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```
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## Controller udev projects
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**Valve's - Steam Devices**
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The Steam Devices package is usually installed when you install Steam on your system, it contains rules for the most common controllers. <br>
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[steam-devices github](https://github.com/ValveSoftware/steam-devices)
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**Game Devices udev**
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The following project is an effort to combine all game devices into one package but it is still early and several are missing.<br>
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[game-devices-udev codeberg](https://codeberg.org/fabiscafe/game-devices-udev)
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**Batocera udev**
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The Batocera project has also combined a list of other controllers that might be missing from the two projects above.
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[Batocera - Controllers github])https://github.com/batocera-linux/batocera.linux/tree/master/package/batocera/controllers)
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## Quick tips on udev installation
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- Installing a udev rule needs administrator root access with sudo and the rules should be put in either the `/etc/udev/rules.d/` or `/run/udev/rules.d` example from above.
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- You can copy the `.rules` from terminal into the directory either from terminal or with sudo access file browser.
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- The rules should be in the `.rules` file format and should be extracted from any `.zip` `.7z` `.tar` or any other compressed format.
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- The udev rule should be added when the RetroDECK or any other software that you want access to the device is not running.
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- After a rule is added you will need to either reload the `udevadm` from terminal by issuing the following command: `sudo udevadm control --reload-rules` or just reboot the system.
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- For SteamOS or other immutable systems udev rules might or might not persistent persist over SteamOS updates (we can't say for certain).
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