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| -rw-r--r-- | Documentation/ABI/testing/sysfs-uevent | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-uevent b/Documentation/ABI/testing/sysfs-uevent new file mode 100644 index 0000000000..0b6227706b --- /dev/null +++ b/Documentation/ABI/testing/sysfs-uevent @@ -0,0 +1,51 @@ +What: /sys/.../uevent +Date: May 2017 +KernelVersion: 4.13 +Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> +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 |