Re: [PATCH 3/5] drm/panel: Add attach/detach callbacks

["dbasehore ." <dbasehore@chromium.org>]

If we want to query the device tree outside of the panel code in
helper functions, we can do this with the struct as is. There's
already a device struct pointer in drm_panel, so I think we can pull
from that.

On Tue, Jun 11, 2019 at 5:25 PM dbasehore . <dbasehore@chromium.org> wrote:
>
> On Tue, Jun 11, 2019 at 1:57 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> >
> > On Mon, Jun 10, 2019 at 09:03:48PM -0700, Derek Basehore wrote:
> > > This adds the attach/detach callbacks. These are for setting up
> > > internal state for the connector/panel pair that can't be done at
> > > probe (since the connector doesn't exist) and which don't need to be
> > > repeatedly done for every get/modes, prepare, or enable callback.
> > > Values such as the panel orientation, and display size can be filled
> > > in for the connector.
> > >
> > > Signed-off-by: Derek Basehore <dbasehore@chromium.org>
> > > ---
> > >  drivers/gpu/drm/drm_panel.c | 14 ++++++++++++++
> > >  include/drm/drm_panel.h     |  4 ++++
> > >  2 files changed, 18 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> > > index 3b689ce4a51a..72f67678d9d5 100644
> > > --- a/drivers/gpu/drm/drm_panel.c
> > > +++ b/drivers/gpu/drm/drm_panel.c
> > > @@ -104,12 +104,23 @@ EXPORT_SYMBOL(drm_panel_remove);
> > >   */
> > >  int drm_panel_attach(struct drm_panel *panel, struct drm_connector *connector)
> > >  {
> > > +     int ret;
> > > +
> > >       if (panel->connector)
> > >               return -EBUSY;
> > >
> > >       panel->connector = connector;
> > >       panel->drm = connector->dev;
> > >
> > > +     if (panel->funcs->attach) {
> > > +             ret = panel->funcs->attach(panel);
> > > +             if (ret < 0) {
> > > +                     panel->connector = NULL;
> > > +                     panel->drm = NULL;
> > > +                     return ret;
> > > +             }
> > > +     }
> >
> > Why can't we just implement this in the drm helpers for everyone, by e.g.
> > storing a dt node in drm_panel? Feels a bit overkill to have these new
> > hooks here.
> >
> > Also, my understanding is that this dt stuff is supposed to be
> > standardized, so this should work.
>
> So do you want all of this information added to the drm_panel struct?
> If we do that, we don't necessarily even need the drm helper function.
> We could just copy the values over here in the drm_panel_attach
> function (and clear them in drm_panel_detach).
>
> > -Daniel
> >
> > > +
> > >       return 0;
> > >  }
> > >  EXPORT_SYMBOL(drm_panel_attach);
> > > @@ -128,6 +139,9 @@ EXPORT_SYMBOL(drm_panel_attach);
> > >   */
> > >  int drm_panel_detach(struct drm_panel *panel)
> > >  {
> > > +     if (panel->funcs->detach)
> > > +             panel->funcs->detach(panel);
> > > +
> > >       panel->connector = NULL;
> > >       panel->drm = NULL;
> > >
> > > diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
> > > index 13631b2efbaa..e136e3a3c996 100644
> > > --- a/include/drm/drm_panel.h
> > > +++ b/include/drm/drm_panel.h
> > > @@ -37,6 +37,8 @@ struct display_timing;
> > >   * struct drm_panel_funcs - perform operations on a given panel
> > >   * @disable: disable panel (turn off back light, etc.)
> > >   * @unprepare: turn off panel
> > > + * @detach: detach panel->connector (clear internal state, etc.)
> > > + * @attach: attach panel->connector (update internal state, etc.)
> > >   * @prepare: turn on panel and perform set up
> > >   * @enable: enable panel (turn on back light, etc.)
> > >   * @get_modes: add modes to the connector that the panel is attached to and
> > > @@ -70,6 +72,8 @@ struct display_timing;
> > >  struct drm_panel_funcs {
> > >       int (*disable)(struct drm_panel *panel);
> > >       int (*unprepare)(struct drm_panel *panel);
> > > +     void (*detach)(struct drm_panel *panel);
> > > +     int (*attach)(struct drm_panel *panel);
> > >       int (*prepare)(struct drm_panel *panel);
> > >       int (*enable)(struct drm_panel *panel);
> > >       int (*get_modes)(struct drm_panel *panel);
> > > --
> > > 2.22.0.rc2.383.gf4fbbf30c2-goog
> > >
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch