Re: [PATCH v8 1/4] drm/panel: Add helper for reading DT rotation

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

On Mon, Oct 7, 2019 at 9:38 AM Sean Paul <sean@poorly.run> wrote:
>
> On Wed, Sep 25, 2019 at 03:58:30PM -0700, Derek Basehore wrote:
> > This adds a helper function for reading the rotation (panel
> > orientation) from the device tree.
> >
> > Signed-off-by: Derek Basehore <dbasehore@chromium.org>
> > Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
>
> The patch LGTM, but I don't see it used anywhere later in the patch? Is there a
> panel driver incoming?

Yeah, the boe-tv101wum-nl6 panel will use it. It's not in the patch
currently sent upstream since I don't want to step on their toes, but
I plan on sending a patch to add it as soon as that is merged.

I could hold back on this patch until that panel driver is merged too.
Another alternative is to throw this into the generic drm_panel code,
but there's no obvious place to put it since DRM seems to leave
reading the DTS up to the panel drivers themselves.

>
> Sean
>
> > ---
> >  drivers/gpu/drm/drm_panel.c | 43 +++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_panel.h     |  9 ++++++++
> >  2 files changed, 52 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> > index 6b0bf42039cf..0909b53b74e6 100644
> > --- a/drivers/gpu/drm/drm_panel.c
> > +++ b/drivers/gpu/drm/drm_panel.c
> > @@ -264,6 +264,49 @@ struct drm_panel *of_drm_find_panel(const struct device_node *np)
> >       return ERR_PTR(-EPROBE_DEFER);
> >  }
> >  EXPORT_SYMBOL(of_drm_find_panel);
> > +
> > +/**
> > + * of_drm_get_panel_orientation - look up the orientation of the panel through
> > + * the "rotation" binding from a device tree node
> > + * @np: device tree node of the panel
> > + * @orientation: orientation enum to be filled in
> > + *
> > + * Looks up the rotation of a panel in the device tree. The orientation of the
> > + * panel is expressed as a property name "rotation" in the device tree. The
> > + * rotation in the device tree is counter clockwise.
> > + *
> > + * Return: 0 when a valid rotation value (0, 90, 180, or 270) is read or the
> > + * rotation property doesn't exist. -EERROR otherwise.
> > + */
> > +int of_drm_get_panel_orientation(const struct device_node *np,
> > +                              enum drm_panel_orientation *orientation)
> > +{
> > +     int rotation, ret;
> > +
> > +     ret = of_property_read_u32(np, "rotation", &rotation);
> > +     if (ret == -EINVAL) {
> > +             /* Don't return an error if there's no rotation property. */
> > +             *orientation = DRM_MODE_PANEL_ORIENTATION_UNKNOWN;
> > +             return 0;
> > +     }
> > +
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     if (rotation == 0)
> > +             *orientation = DRM_MODE_PANEL_ORIENTATION_NORMAL;
> > +     else if (rotation == 90)
> > +             *orientation = DRM_MODE_PANEL_ORIENTATION_RIGHT_UP;
> > +     else if (rotation == 180)
> > +             *orientation = DRM_MODE_PANEL_ORIENTATION_BOTTOM_UP;
> > +     else if (rotation == 270)
> > +             *orientation = DRM_MODE_PANEL_ORIENTATION_LEFT_UP;
> > +     else
> > +             return -EINVAL;
> > +
> > +     return 0;
> > +}
> > +EXPORT_SYMBOL(of_drm_get_panel_orientation);
> >  #endif
> >
> >  MODULE_AUTHOR("Thierry Reding <treding@nvidia.com>");
> > diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
> > index 624bd15ecfab..d16158deacdc 100644
> > --- a/include/drm/drm_panel.h
> > +++ b/include/drm/drm_panel.h
> > @@ -34,6 +34,8 @@ struct drm_device;
> >  struct drm_panel;
> >  struct display_timing;
> >
> > +enum drm_panel_orientation;
> > +
> >  /**
> >   * struct drm_panel_funcs - perform operations on a given panel
> >   *
> > @@ -165,11 +167,18 @@ int drm_panel_get_modes(struct drm_panel *panel);
> >
> >  #if defined(CONFIG_OF) && defined(CONFIG_DRM_PANEL)
> >  struct drm_panel *of_drm_find_panel(const struct device_node *np);
> > +int of_drm_get_panel_orientation(const struct device_node *np,
> > +                              enum drm_panel_orientation *orientation);
> >  #else
> >  static inline struct drm_panel *of_drm_find_panel(const struct device_node *np)
> >  {
> >       return ERR_PTR(-ENODEV);
> >  }
> > +static inline int of_drm_get_panel_orientation(const struct device_node *np,
> > +             enum drm_panel_orientation *orientation)
> > +{
> > +     return -ENODEV;
> > +}
> >  #endif
> >
> >  #endif
> > --
> > 2.23.0.351.gc4317032e6-goog
> >
>
> --
> Sean Paul, Software Engineer, Google / Chromium OS