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 22:15:28 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Sam Ravnborg <sam@...nborg.org>, Hsin-Yi Wang <hsinyi@...omium.org>
Cc:     Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        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,

On 6/6/22 21:20, Sam Ravnborg wrote:
> 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.

The downside of moving this up is that it will break drivers which don't
use c99 style named-struct-field initializers for there drm_panel_funcs.

I admit that no drivers should be using the old style struct init, but
are we sure that that is the case?

Regards,

Hans



> 
> 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
>