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

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Message-ID: <20191007163822.GA126146@art_vandelay>
Date:   Mon, 7 Oct 2019 12:38:22 -0400
From:   Sean Paul <sean@...rly.run>
To:     Derek Basehore <dbasehore@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, 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@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v8 1/4] drm/panel: Add helper for reading DT rotation

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?

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