Re: [PATCH v2 1/2] drm/vc4: crtc: Rework a bit the CRTC state code

[Maxime Ripard <maxime@cerno.tech>]

Hi Dave,

On Wed, Sep 23, 2020 at 03:59:04PM +0100, Dave Stevenson wrote:
> Hi Maxime
> 
> On Wed, 23 Sep 2020 at 09:40, Maxime Ripard <maxime@cerno.tech> wrote:
> >
> > The current CRTC state reset hook in vc4 allocates a vc4_crtc_state
> > structure as a drm_crtc_state, and relies on the fact that vc4_crtc_state
> > embeds drm_crtc_state as its first member, and therefore can be safely
> > casted.
> 
> s/casted/cast
> 
> > However, this is pretty fragile especially since there's no check for this
> > in place, and we're going to need to access vc4_crtc_state member at reset
> > so this looks like a good occasion to make it more robust.
> >
> > Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> > Tested-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> 
> Based on the issue I perceived with the previous patch, I'm happy. I
> haven't thought about how the framework handles losing the state, but
> that's not the driver's problem.
> 
> There is still an implicit assumption that drm_crtc_state is the first
> member from the implementation of to_vc4_crtc_state in vc4_drv.h. To
> make it even more robust that could be a container_of instead. I
> haven't checked for any other places that make the assumption though.

Good catch, I'll send another patch to fix it

> Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

Does it apply to the second patch as well?

Thanks!
Maxime

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