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

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Date:   Tue, 8 Oct 2019 10:56:23 -0400
From:   Sean Paul <sean@...rly.run>
To:     "dbasehore ." <dbasehore@...omium.org>
Cc:     Sean Paul <sean@...rly.run>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        CK Hu <ck.hu@...iatek.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Intel Graphics <intel-gfx@...ts.freedesktop.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v8 1/4] drm/panel: Add helper for reading DT rotation

On Mon, Oct 07, 2019 at 03:12:00PM -0700, dbasehore . wrote:
> On Mon, Oct 7, 2019 at 9:38 AM Sean Paul <sean@...rly.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@...omium.org>
> > > Reviewed-by: Sam Ravnborg <sam@...nborg.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.

Yeah, I think it's probably best. I don't anticipate any changes will be
required, but it's always best to review the code end-to-end.

I haven't checked in on that review, but if it's close to landing, you can also
add a patch to this stack that is based on the in-flight patches. That way we can
get all the review out of the way and then when the panel lands, we can apply
your add-on with the rest of the series.

Sean

> 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@...dia.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

-- 
Sean Paul, Software Engineer, Google / Chromium OS