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44 lines
2 KiB
Markdown
44 lines
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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## 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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## Adding Controllers
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For these controllers to being recognized but the system and so by RetroDECK is needed to set their own udev rule on SteamOS.
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Udev rules are used to allow and manage the access to a specific third party usb device, so without a proper udev rule some devices such as the following ones could not be used by RetroDECK nor by the system.
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Some notes on the udev rules:
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- Setting an udev rule needs root access.
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- The udev rule must be added when the emulator is not running, if it's running it must be restarted to acknowledge the change.
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- The udev rules seems to be persistent even after a SteamOS update.
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> **NOTE:** If running other Linux distributions the procedure might have some difference, please refer to a proper documentation or a web search.
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