media: debugfs-cec-error-inj: document CEC error inj debugfs ABI

What:		/sys/kernel/debug/cec/*/error-inj

Date:		March 2018

Contact:	Hans Verkuil <hans.verkuil@cisco.com>

Description:

The CEC Framework allows for CEC error injection commands through

debugfs. Drivers that support this will create an error-inj file

through which the error injection commands can be given.

The basic syntax is as follows:

Leading spaces/tabs are ignored. If the next character is a '#' or the

end of the line was reached, then the whole line is ignored. Otherwise

a command is expected.

It is up to the driver to decide what commands to implement. The only

exception is that the command 'clear' without any arguments must be

implemented and that it will remove all current error injection

commands.

This ensures that you can always do 'echo clear >error-inj' to clear any

error injections without having to know the details of the driver-specific

commands.

Note that the output of 'error-inj' shall be valid as input to 'error-inj'.

So this must work:

	$ cat error-inj >einj.txt

	$ cat einj.txt >error-inj

Other than these basic rules described above this ABI is not considered

stable and may change in the future.

Drivers that implement this functionality must document the commands as

part of the CEC documentation and must keep that documentation up to date

when changes are made.

The following CEC error injection implementations exist:

- Documentation/media/uapi/cec/cec-pin-error-inj.rst

F:	include/uapi/linux/cec.h

F:	include/uapi/linux/cec-funcs.h

F:	Documentation/devicetree/bindings/media/cec.txt

F:	Documentation/ABI/testing/debugfs-cec-error-inj

CEC GPIO DRIVER

M:	Hans Verkuil <hans.verkuil@cisco.com>