linux-kernel - Re: [PATCH v4 1/8] drm/panel: Add an API drm_panel_get_orientation() to return panel orientation

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Date:   Mon, 6 Jun 2022 21:20:43 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Hsin-Yi Wang <hsinyi@...omium.org>
Cc:     Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthias Brugger <matthias.bgg@...il.com>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        Rob Clark <robdclark@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/8] drm/panel: Add an API drm_panel_get_orientation()
 to return panel orientation

Hi Hsin-Yi,
On Mon, Jun 06, 2022 at 11:24:24PM +0800, Hsin-Yi Wang wrote:
> Panels usually call drm_connector_set_panel_orientation(), which is
> later than drm/kms driver calling drm_dev_register(). This leads to a
> WARN().
> 
> The orientation property is known earlier. For example, some panels
> parse the property through device tree during probe.
> 
> Add an API to return the property from panel to drm/kms driver, so the
> drivers are able to call drm_connector_set_panel_orientation() before
> drm_dev_register().
> 
> Suggested-by: Hans de Goede <hdegoede@...hat.com>
> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> Reviewed-by: Hans de Goede <hdegoede@...hat.com>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
> ---
> v3->v4: Add a blank line.
> ---
>  drivers/gpu/drm/drm_panel.c |  9 +++++++++
>  include/drm/drm_panel.h     | 10 ++++++++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> index f634371c717a..e12056cfeca8 100644
> --- a/drivers/gpu/drm/drm_panel.c
> +++ b/drivers/gpu/drm/drm_panel.c
> @@ -223,6 +223,15 @@ int drm_panel_get_modes(struct drm_panel *panel,
>  }
>  EXPORT_SYMBOL(drm_panel_get_modes);
>  
> +enum drm_panel_orientation drm_panel_get_orientation(struct drm_panel *panel)
const as mentioned by Stephen.

> +{
> +	if (panel && panel->funcs && panel->funcs->get_orientation)
> +		return panel->funcs->get_orientation(panel);
> +
> +	return DRM_MODE_PANEL_ORIENTATION_UNKNOWN;
> +}
> +EXPORT_SYMBOL(drm_panel_get_orientation);
> +
>  #ifdef CONFIG_OF
>  /**
>   * of_drm_find_panel - look up a panel using a device tree node
> diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
> index d279ee455f01..5dadbf3b0370 100644
> --- a/include/drm/drm_panel.h
> +++ b/include/drm/drm_panel.h
> @@ -133,6 +133,15 @@ struct drm_panel_funcs {
>  	 * Allows panels to create panels-specific debugfs files.
>  	 */
>  	void (*debugfs_init)(struct drm_panel *panel, struct dentry *root);
> +
> +	/**
> +	 * @get_orientation:
> +	 *
> +	 * Return the panel orientation set by device tree or EDID.
> +	 *
> +	 * This function is optional.
> +	 */
> +	enum drm_panel_orientation (*get_orientation)(struct drm_panel *panel);

Please move this up so it is together with the other get_* methods, in
alphabetic order. That is, right after get_modes(), and then this also
matches the order in the .c file with is extra bonus.

With the two fixes:
Reviewed-by: Sam Ravnborg <sam@...nborg.org>

>  };
>  
>  /**
> @@ -202,6 +211,7 @@ int drm_panel_enable(struct drm_panel *panel);
>  int drm_panel_disable(struct drm_panel *panel);
>  
>  int drm_panel_get_modes(struct drm_panel *panel, struct drm_connector *connector);
> +enum drm_panel_orientation drm_panel_get_orientation(struct drm_panel *panel);
>  
>  #if defined(CONFIG_OF) && defined(CONFIG_DRM_PANEL)
>  struct drm_panel *of_drm_find_panel(const struct device_node *np);
> -- 
> 2.36.1.255.ge46751e96f-goog