Hi Stephen,
On Wed, Nov 16, 2022 at 10:57:02AM +1100, Stephen Rothwell wrote:
> Hi all,
>
> Today's linux-next merge of the drm-misc tree got a conflict in:
>
> drivers/gpu/drm/vc4/vc4_hdmi.c
>
> between commit:
>
> 682f99b8ae88 ("drm/vc4: hdmi: Take our lock to reset the link")
>
> from the origin tree and commits:
>
> d218750805a3 ("drm/vc4: hdmi: Pass vc4_hdmi to vc4_hdmi_supports_scrambling()")
> 0a99962c0dbf ("drm/vc4: hdmi: Fix pointer dereference before check")
>
> from the drm-misc tree.
>
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging. You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
>
> --
> Cheers,
> Stephen Rothwell
>
> diff --cc drivers/gpu/drm/vc4/vc4_hdmi.c
> index d7fcc7a4c082,6b223a5fcf6f..000000000000
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@@ -349,12 -348,9 +348,13 @@@ static int vc4_hdmi_reset_link(struct d
> if (!crtc_state->active)
> return 0;
>
> + mutex_lock(&vc4_hdmi->mutex);
> +
> - if (!vc4_hdmi_supports_scrambling(encoder)) {
> + vc4_hdmi = connector_to_vc4_hdmi(connector);
> - if (!vc4_hdmi_supports_scrambling(vc4_hdmi))
> ++ if (!vc4_hdmi_supports_scrambling(vc4_hdmi)) {
> + mutex_unlock(&vc4_hdmi->mutex);
> return 0;
> + }
>
> scrambling_needed = vc4_hdmi_mode_needs_scrambling(&vc4_hdmi->saved_adjusted_mode,
> vc4_hdmi->output_bpc,
This resolution is not quite right, as pointed out by clang:
drivers/gpu/drm/vc4/vc4_hdmi.c:351:14: error: variable 'vc4_hdmi' is uninitialized when used here [-Werror,-Wuninitialized]
mutex_lock(&vc4_hdmi->mutex);
^~~~~~~~
./include/linux/mutex.h:187:44: note: expanded from macro 'mutex_lock'
#define mutex_lock(lock) mutex_lock_nested(lock, 0)
^~~~
drivers/gpu/drm/vc4/vc4_hdmi.c:322:27: note: initialize the variable 'vc4_hdmi' to silence this warning
struct vc4_hdmi *vc4_hdmi;
^
= NULL
1 error generated.
Obviously, the assignment of vc4_hdmi should be before mutex_lock().
Cheers,
Nathan
