On Thu, May 30, 2024 at 07:33:59AM -0700, Doug Anderson wrote:
> Hi,
>
> On Tue, May 28, 2024 at 4:52 PM Dmitry Baryshkov
> <dmitry.baryshkov@xxxxxxxxxx> wrote:
> >
> > Add a fat warning against adding new panel compatibles to the panel-edp
> > driver. All new users of the eDP panels are supposed to use the generic
> > "edp-panel" compatible device on the AUX bus. The remaining compatibles
> > are either used by the existing DT or were used previously and are
> > retained for backwards compatibility.
> >
> > Suggested-by: Doug Anderson <dianders@xxxxxxxxxxxx>
> > Reviewed-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > ---
> > drivers/gpu/drm/panel/panel-edp.c | 18 +++++++++++++++++-
> > 1 file changed, 17 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
> > index 6db277efcbb7..95b25ec67168 100644
> > --- a/drivers/gpu/drm/panel/panel-edp.c
> > +++ b/drivers/gpu/drm/panel/panel-edp.c
> > @@ -1776,7 +1776,23 @@ static const struct of_device_id platform_of_match[] = {
> > {
> > /* Must be first */
> > .compatible = "edp-panel",
> > - }, {
> > + },
> > + /*
> > + * Do not add panels to the list below unless they cannot be handled by
> > + * the generic edp-panel compatible.
> > + *
> > + * The only two valid reasons are:
> > + * - because of the panel issues (e.g. broken EDID or broken
> > + * identification),
> > + * - because the platform which uses the panel didn't wire up the AUX
> > + * bus properly.
> > + *
> > + * In all other cases the platform should use the aux-bus and declare
> > + * the panel using the 'edp-panel' compatible as a device on the AUX
> > + * bus. The lack of the aux-bus support is not a valid case. Platforms
> > + * are urged to be converted to declaring panels in a proper way.
>
> I'm still at least slightly confused by the wording. What is "the lack
> of the aux-bus support". I guess this is different from the valid
> reason of "the platform which uses the panel didn't wire up the AUX
> bus properly" but I'm not sure how. Maybe you can explain?
>
> I guess I'd write it like this:
>
> /*
> * Do not add panels to the list below unless they cannot be handled by
> * the generic edp-panel compatible.
> *
> * The only two valid reasons are:
> * - because of the panel issues (e.g. broken EDID or broken
> * identification).
> * - because the platform which uses the panel didn't wire up the AUX
> * bus properly. NOTE that, though this is a marginally valid reason,
> * some justification needs to be made for why the platform can't
> * wire up the AUX bus properly.
> *
> * In all other cases the platform should use the aux-bus and declare
> * the panel using the 'edp-panel' compatible as a device on the AUX
> * bus.
> */
>
> What do you think? In any case, it probably doesn't matter much. The
> important thing is some sort of warning here telling people not to add
> to the table. In that sense:
Ack, I'l update the wording in a similar way.
>
> Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
--
With best wishes
Dmitry
