On 10/27/23 09:17, Boris Brezillon wrote:
Hi Danilo,
On Thu, 26 Oct 2023 18:13:00 +0200
Danilo Krummrich <dakr@xxxxxxxxxx> wrote:
+
+ /**
+ * @update_job_credits: Called once the scheduler is considering this
+ * job for execution.
+ *
+ * Drivers may use this to update the job's submission credits, which is
+ * useful to e.g. deduct the number of native fences which have been
+ * signaled meanwhile.
+ *
+ * The callback must either return the new number of submission credits
+ * for the given job, or zero if no update is required.
+ *
+ * This callback is optional.
+ */
+ u32 (*update_job_credits)(struct drm_sched_job *sched_job);
I'm copying my late reply to v2 here so it doesn't get lost:
I keep thinking it'd be simpler to make this a void function that
updates s_job->submission_credits directly. I also don't see the
problem with doing a sanity check on job->submission_credits. I mean,
if the driver is doing something silly, you can't do much to prevent it
anyway, except warn the user that something wrong has happened. If you
want to
WARN_ON(job->submission_credits == 0 ||
job->submission_credits > job_old_submission_credits);
that's fine. But none of this sanity checking has to do with the
function prototype/semantics, and I'm still not comfortable with this 0
=> no-change. If there's no change, we should just leave
job->submission_credits unchanged (or return job->submission_credits)
instead of inventing a new special case.
If we can avoid letting drivers change fields of generic structures directly
without any drawbacks I think we should avoid it. Currently, drivers shouldn't
have the need to mess with job->credits directly. The initial value is set
through drm_sched_job_init() and is updated through the return value of
update_job_credits().
I'm fine getting rid of the 0 => no-change semantics though. Instead we can just
WARN() on 0. However, if we do that I'd also want to change it for
drm_sched_job_init() (where 0 currently defaults to 1) such that we accept 0, but
WARN() accordingly.
I think it's consequent to either consistently give 0 a different meaning or just
accept it but WARN() on it.
Regards,
Boris
