Hi Am 30.09.24 um 09:01 schrieb Maxime Ripard:
Hi, On Fri, Sep 27, 2024 at 04:46:16PM GMT, Lyude Paul wrote:Something I discovered while writing rvkms since some versions of the driver didn't have a filled out atomic_update function - we mention that this callback is "optional", but we don't actually check whether it's NULL or not before calling it. As a result, we'll segfault if it's not filled in. rvkms rvkms.0: [drm:drm_atomic_helper_commit_modeset_disables] modeset on [ENCODER:36:Virtual-36] BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 0 P4D 0 Oops: Oops: 0010 [#1] PREEMPT SMP NOPTI Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20240813-1.fc40 08/13/2024 RIP: 0010:0x0 So, let's fix that. Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx> Fixes: c2fcd274bce5 ("drm: Add atomic/plane helpers") Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx Cc: <stable@xxxxxxxxxxxxxxx> # v3.19+So we had kind of a similar argument with drm_connector_init early this year, but I do agree we shouldn't fault if we're missing a callback. I do wonder how we can implement a plane without atomic_update though? Do we have drivers in such a case?
That would likely be an output with an entirely static display. Hard to imaging, I think.
If not, a better solution would be to make it mandatory and check it when registering.
Although I r-b'ed the patch already, I'd also prefer this solution.
Maxime
-- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)
