Re: [Intel-gfx] [PATCH 01/15] gpu/drm: make drm_add_edid_modes() consistent when updating connector->display_info

Claudio Suarez
2021-10-15T19:24:29Z

On Fri, Oct 15, 2021 at 03:03:13PM +0300, Ville Syrjälä wrote:
> On Fri, Oct 15, 2021 at 01:36:59PM +0200, Claudio Suarez wrote:
> > According to the documentation, drm_add_edid_modes
> > "... Also fills out the &drm_display_info structure and ELD in @connector
> > with any information which can be derived from the edid."
> >
> > drm_add_edid_modes accepts a struct edid *edid parameter which may have a
> > value or may be null. When it is not null, connector->display_info and
> > connector->eld are updated according to the edid. When edid=NULL, only
> > connector->eld is reset. Reset connector->display_info to be consistent
> > and accurate.
> >
> > Signed-off-by: Claudio Suarez <cssk@net-c.es>
> > ---
> > drivers/gpu/drm/drm_edid.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > index 6325877c5fd6..6cbe09b2357c 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -5358,10 +5358,12 @@ int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid)
> >
> > if (edid == NULL) {
> > clear_eld(connector);
> > + drm_reset_display_info(connector);
> > return 0;
> > }
> > if (!drm_edid_is_valid(edid)) {
> > clear_eld(connector);
> > + drm_reset_display_info(connector);
>
> Looks easier if you pull both of those out from these branches and
> just call them unconditionally at the start.

After looking at the full code, I am not sure. This is the code:
==================
int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid)
{
int num_modes = 0;
u32 quirks;

if (edid == NULL) {
clear_eld(connector);
drm_reset_display_info(connector); <--- added by me
return 0;
}
if (!drm_edid_is_valid(edid)) {
clear_eld(connector);
drm_reset_display_info(connector); <--- added by me
drm_warn(connector->dev, "%s: EDID invalid.\n",
connector->name);
return 0;
}

drm_edid_to_eld(connector, edid);

quirks = drm_add_display_info(connector, edid);
etc...
=================

If we move those out of these branches and edid != NULL, we are executing an
unnecessary clear_eld(connector) and an unnecessary drm_reset_display_info(connector)
because the fields will be set in the next drm_edid_to_eld(connector, edid) and
drm_add_display_info(connector, edid)

Do we want this ?

BR
Claudio Suarez