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