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51 lines
2.3 KiB
51 lines
2.3 KiB
What: /sys/.../uevent |
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Date: May 2017 |
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KernelVersion: 4.13 |
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Contact: Linux kernel mailing list <[email protected]> |
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Description: |
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Enable passing additional variables for synthetic uevents that |
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are generated by writing /sys/.../uevent file. |
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Recognized extended format is:: |
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ACTION [UUID [KEY=VALUE ...] |
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The ACTION is compulsory - it is the name of the uevent |
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action (``add``, ``change``, ``remove``). There is no change |
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compared to previous functionality here. The rest of the |
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extended format is optional. |
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You need to pass UUID first before any KEY=VALUE pairs. |
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The UUID must be in ``xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx`` |
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format where 'x' is a hex digit. The UUID is considered to be |
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a transaction identifier so it's possible to use the same UUID |
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value for one or more synthetic uevents in which case we |
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logically group these uevents together for any userspace |
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listeners. The UUID value appears in uevent as |
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``SYNTH_UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx`` environment |
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variable. |
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If UUID is not passed in, the generated synthetic uevent gains |
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``SYNTH_UUID=0`` environment variable automatically. |
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The KEY=VALUE pairs can contain alphanumeric characters only. |
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It's possible to define zero or more pairs - each pair is then |
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delimited by a space character ' '. Each pair appears in |
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synthetic uevent as ``SYNTH_ARG_KEY=VALUE``. That means the KEY |
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name gains ``SYNTH_ARG_`` prefix to avoid possible collisions |
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with existing variables. |
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Example of valid sequence written to the uevent file:: |
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add fe4d7c9d-b8c6-4a70-9ef1-3d8a58d18eed A=1 B=abc |
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This generates synthetic uevent including these variables:: |
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ACTION=add |
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SYNTH_ARG_A=1 |
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SYNTH_ARG_B=abc |
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SYNTH_UUID=fe4d7c9d-b8c6-4a70-9ef1-3d8a58d18eed |
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Users: |
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udev, userspace tools generating synthetic uevents
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