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?
If not, a better solution would be to make it mandatory and check it
when registering.
Maxime
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