[igt-dev] [PATCH i-g-t] xe_live_ktest: Use xe_live_test kernel module

[Lucas De Marchi]

On Mon, Jan 15, 2024 at 08:52:07PM +0100, Mauro Carvalho Chehab wrote:
>On Mon, 15 Jan 2024 09:21:35 +0200
>Jani Nikula <jani.nikula at linux.intel.com> wrote:
>
>> On Mon, 15 Jan 2024, Mauro Carvalho Chehab <mauro.chehab at linux.intel.com> wrote:
>> > On 1/12/24 15:29, Lucas De Marchi wrote:
>> >>> On such case, you should document kunit_debugfs at Documentation/ABI.
>> >>
>> >> debugfs is not part of ABI.
>> >
>> > That's arguable. Check Documentation/ABI and you'll see several debugfs
>> > nodes documented there.
>>
>> I guess you could argue documenting your debugfs under Documentation/ABI
>> makes it ABI, but I'd avoid doing that. Usually we use debugfs precisely
>> to avoid the burden of ABI and all the baggage that brings.
>
>Placing things at debugfs "precisely to avoid the burden of ABI and all
>the baggage that brings" sounds a bad practice to me, but you can ask
>others at LKML and see if this is a acceptable.
>
>My understanding is that, if userspace tools rely on what's there at
>debugfs, and a change break such tools, there is a high chance that
>such change will end being reverted - at best, it will surely provide
>some flame wars.
>
>I remember we had some troubles related to trace logic in the past,
>due to something similar: even not originally meant to provide a stable
>ABI, and being under debugfs, there were some changes breaking userspace
>which caused lots of discussions. Can't remember anymore if the changes
>were reverted or not, but at the end ftrace ABI was considered as stable.

ftrace provides a way for you to read the format of the tracepoint and
use it (API). If you did it otherwise and hardcoded the format (ABI),
you are on your own as tracepoints in the kernel keep changing.
Try grepping "tracepoint" in the last pull requests.

>I have an userspace program which depends on it (rasdaemon).

if there's a real tool that needs the info, then it should _not_ be in
debugfs.  I'm not sure what how kunit handles that, maybe ask them as
this is getting very off topic here.

Lucas De Marchi