diff mbox series

[v2,1/3] drm/panel-edp: add fat warning against adding new panel compatibles

Message ID 20240529-edp-panel-drop-v2-1-fcfc457fc8dd@linaro.org
State New
Headers show
Series drm/panel-edp: remove several legacy compatibles used by the driver | expand

Commit Message

Dmitry Baryshkov May 28, 2024, 11:52 p.m. UTC 
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@chromium.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/gpu/drm/panel/panel-edp.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

Comments

Dmitry Baryshkov May 30, 2024, 11:11 p.m. UTC | #1 
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@linaro.org> 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@chromium.org>
> > Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > ---
> >  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@chromium.org>
diff mbox series

Patch

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.
+	 */
+	{
 		.compatible = "auo,b101ean01",
 		.data = &auo_b101ean01,
 	}, {