48 lines
2.2 KiB
Plaintext
48 lines
2.2 KiB
Plaintext
|
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
|