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linux-imx/Documentation/ABI/testing/sysfs-uevent
Mauro Carvalho Chehab 906e4af935 docs: ABI: sysfs-uevent: make it compatible with ReST output 
- Replace " by ``, in order to use monospaced fonts;
- mark literal blocks as such.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/63904cc9b6a8581c5fc2ea1dca5d925874c67372.1604042072.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-10-30 13:07:02 +01:00

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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