Re: [PATCH v9 09/10] drm/doc: document some tracepoints as uAPI

[Pierre-Eric Pelloux-Prayer <pierre-eric@damsy.net>]

Hi,

Le 14/05/2025 à 14:53, Philipp Stanner a écrit :
> On Thu, 2025-04-24 at 10:38 +0200, Pierre-Eric Pelloux-Prayer wrote:
>> This commit adds a document section in drm-uapi.rst about
>> tracepoints,
>> and mark the events gpu_scheduler_trace.h as stable uAPI.
>>
>> The goal is to explicitly state that tools can rely on the fields,
>> formats and semantics of these events.
>>
>> Acked-by: Lucas Stach <l.stach@pengutronix.de>
>> Acked-by: Maíra Canal <mcanal@igalia.com>
>> Reviewed-by: Christian König <christian.koenig@amd.com>
>> Signed-off-by: Pierre-Eric Pelloux-Prayer
>> <pierre-eric.pelloux-prayer@amd.com>
>> ---
>>   Documentation/gpu/drm-uapi.rst                | 19
>> +++++++++++++++++++
>>   .../gpu/drm/scheduler/gpu_scheduler_trace.h   | 19
>> +++++++++++++++++++
>>   2 files changed, 38 insertions(+)
>>
>> diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-
>> uapi.rst
>> index 69f72e71a96e..4863a4deb0ee 100644
>> --- a/Documentation/gpu/drm-uapi.rst
>> +++ b/Documentation/gpu/drm-uapi.rst
>> @@ -693,3 +693,22 @@ dma-buf interoperability
>>   
>>   Please see Documentation/userspace-api/dma-buf-alloc-exchange.rst
>> for
>>   information on how dma-buf is integrated and exposed within DRM.
>> +
>> +
>> +Trace events
>> +============
>> +
>> +See Documentation/trace/tracepoints.rst for information about using
>> +Linux Kernel Tracepoints.
>> +In the DRM subsystem, some events are considered stable uAPI to
>> avoid
>> +breaking tools (e.g.: GPUVis, umr) relying on them. Stable means
>> that fields
>> +cannot be removed, nor their formatting updated. Adding new fields
>> is
>> +possible, under the normal uAPI requirements.
>> +
>> +Stable uAPI events
>> +------------------
>> +
>> +From ``drivers/gpu/drm/scheduler/gpu_scheduler_trace.h``
>> +
>> +.. kernel-doc::  drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
>> +   :doc: uAPI trace events
>> \ No newline at end of file
>> diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
>> b/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
>> index 781b20349389..7e840d08ef39 100644
>> --- a/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
>> +++ b/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
>> @@ -32,6 +32,25 @@
>>   #define TRACE_SYSTEM gpu_scheduler
>>   #define TRACE_INCLUDE_FILE gpu_scheduler_trace
>>   
>> +/**
>> + * DOC: uAPI trace events
>> + *
>> + * ``drm_sched_job_queue``, ``drm_sched_job_run``,
>> ``drm_sched_job_add_dep``,
>> + * ``drm_sched_job_done`` and ``drm_sched_job_unschedulable`` are
>> considered
>> + * stable uAPI.
>> + *
>> + * Common trace events attributes:
>> + *
>> + * * ``dev``   - the dev_name() of the device running the job.
>> + *
>> + * * ``ring``  - the hardware ring running the job. Together with
>> ``dev`` it
>> + *   uniquely identifies where the job is going to be executed.
>> + *
>> + * * ``fence`` - the &dma_fence.context and the &dma_fence.seqno of
>> + *   &drm_sched_fence.finished
>> + *
>> + */
> 
> For my understanding, why do you use the double apostrophes here?

To get similar formatting to function arguments and make the output a bit nicer to read.

> 
> Also, the linking for the docu afair here two requires you to write
> 
> &struct dma_fence.seqno
> 
> If I am not mistaken
> 
> https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#highlights-and-cross-references

Indeed, thanks. I fixed this.

Pierre-Eric

> 
> 
> P.
> 
>> +
>>   DECLARE_EVENT_CLASS(drm_sched_job,
>>   	    TP_PROTO(struct drm_sched_job *sched_job, struct
>> drm_sched_entity *entity),
>>   	    TP_ARGS(sched_job, entity),