[PATCH] drm/bridge: anx7625: Fix invalid EDID size

[Maxime Ripard]

On Mon, Jun 30, 2025 at 09:46:40AM +0200, Loic Poulain wrote:
> Hi Maxime,
> 
> On Mon, Jun 30, 2025 at 9:07 AM Maxime Ripard <mripard at kernel.org> wrote:
> > On Sun, Jun 29, 2025 at 04:38:36AM +0200, Loic Poulain wrote:
> > > DRM checks EDID block count against allocated size in drm_edid_valid
> > > function. We have to allocate the right EDID size instead of the max
> > > size to prevent the EDID to be reported as invalid.
> > >
> > > Fixes: 7c585f9a71aa ("drm/bridge: anx7625: use struct drm_edid more")
> > > Signed-off-by: Loic Poulain <loic.poulain at oss.qualcomm.com>
> > > ---
> > >  drivers/gpu/drm/bridge/analogix/anx7625.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
> > > index 8a9079c2ed5c..5a81d1bfc815 100644
> > > --- a/drivers/gpu/drm/bridge/analogix/anx7625.c
> > > +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
> > > @@ -1801,7 +1801,7 @@ static const struct drm_edid *anx7625_edid_read(struct anx7625_data *ctx)
> > >               return NULL;
> > >       }
> > >
> > > -     ctx->cached_drm_edid = drm_edid_alloc(edid_buf, FOUR_BLOCK_SIZE);
> > > +     ctx->cached_drm_edid = drm_edid_alloc(edid_buf, edid_num * ONE_BLOCK_SIZE);
> > >       kfree(edid_buf);
> >
> > Do we need to cache the whole EDIDs? AFAIU, it's only ever used to get
> > the manufacturer name, which fits into a u32 / 4 u8. We should probably
> > just cache that.
> 
> While the cached EDID is indeed used internally to retrieve the
> product ID, its content is also returned via the DRM read_edid
> callback. This value is then used by the DRM core to enumerate
> available display modes, and likely also when reading EDID from sysfs.

You still don't need to allocate and store a copy of the EDIDs in your
driver to implement what you listed so far.

Maxime
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