Re: [PATCH v2] drm/sched: Guard against NULL dev in drm_sched_job trace event

[Danilo Krummrich]

On Tue Aug 25, 2026 at 2:11 PM CEST, Philipp Stanner wrote:
> On Tue, 2026-08-25 at 14:02 +0200, Danilo Krummrich wrote:
>> 
>
> […]
>
>> 
>> I don't think that we should make such changes for Kunit tests only; it implies
>> that a NULL dev now would be a valid value for the scheduler.
>
> Strictly speaking we don't allow for the device pointer to be NULL, so
> you might be right. However, it actually is only used for creating
> debug prints, so…
>
>
>> 
>> Why can't we have the Kunit test create a fake device for this? For instance,
>> this is where struct faux_device becomes useful.
>
> Wouldn't that be the same result as printing "NULL device"?
>
> Many DRM print helpers do the latter already. __drm_dev_vprintk() takes
> dev == NULL into account.
> So one might argue that making the print-functions all robust against
> NULL would be the more consistent thing.

The dev_printk() primitives already do this, but that's not the point. The point
is that a scheduler with a NULL device makes no sense in the first place, so we
shouldn't support it -- especially not when it is just for a Kunit test that can
easily satisfy the API by calling faux_device_create().