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 <ly...@redhat.com>
Fixes: c2fcd274bce5 ("drm: Add atomic/plane helpers")
Cc: dri-devel@lists.freedesktop.org
Cc: <sta...@vger.kernel.org> # 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
--
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Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
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