[PATCH v2 4/9] drm/doc: fix drm_plane_type docs

[Daniel Vetter]

On Thu, Dec 17, 2020 at 12:32:15PM +0100, Simon Ser wrote:
> The docs for enum drm_plane_type mention legacy IOCTLs, however the
> plane type is not tied to legacy IOCTLs, the drm_cursor.primary and
> cursor fields are. Add a small paragraph to reference these.
> 
> Instead, document expectations for primary and cursor planes for
> non-legacy userspace. Note that these docs are for driver developers,
> not userspace developers, so internal kernel APIs are mentionned.
> 
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Pekka Paalanen <ppaalanen at gmail.com>
> ---
>  include/drm/drm_plane.h | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> index 1d82b264e5e4..5b180d07788e 100644
> --- a/include/drm/drm_plane.h
> +++ b/include/drm/drm_plane.h
> @@ -538,10 +538,14 @@ struct drm_plane_funcs {
>   *
>   * For compatibility with legacy userspace, only overlay planes are made
>   * available to userspace by default. Userspace clients may set the
> - * DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that they
> + * &DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that they
>   * wish to receive a universal plane list containing all plane types. See also
>   * drm_for_each_legacy_plane().
>   *
> + * In addition to setting each plane's type, drivers need to setup the
> + * &drm_crtc.primary and optionally &drm_crtc.cursor pointers for legacy
> + * IOCTLs. See drm_crtc_init_with_planes().
> + *
>   * WARNING: The values of this enum is UABI since they're exposed in the "type"
>   * property.
>   */
> @@ -557,19 +561,28 @@ enum drm_plane_type {
>  	/**
>  	 * @DRM_PLANE_TYPE_PRIMARY:
>  	 *
> -	 * Primary planes represent a "main" plane for a CRTC.  Primary planes
> -	 * are the planes operated upon by CRTC modesetting and flipping
> -	 * operations described in the &drm_crtc_funcs.page_flip and
> -	 * &drm_crtc_funcs.set_config hooks.
> +	 * A primary plane attached to a CRTC is the most likely to be able to
> +	 * light up the CRTC when no scaling/cropping is used and the plane
> +	 * covers the whole CRTC.
> +	 *
> +	 * In addition to setting a plane type to primary, drivers need to
> +	 * setup the &drm_crtc.primary pointer for legacy IOCTLs. See
> +	 * drm_crtc_init_with_planes().

After you brought it up I'm actually fine with not duplicating this.
Either way:

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

>  	 */
>  	DRM_PLANE_TYPE_PRIMARY,
>  
>  	/**
>  	 * @DRM_PLANE_TYPE_CURSOR:
>  	 *
> -	 * Cursor planes represent a "cursor" plane for a CRTC.  Cursor planes
> -	 * are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and
> -	 * DRM_IOCTL_MODE_CURSOR2 IOCTLs.
> +	 * A cursor plane attached to a CRTC is more likely to be able to be
> +	 * enabled when no scaling/cropping is used and the framebuffer has the
> +	 * size indicated by &drm_mode_config.cursor_width and
> +	 * &drm_mode_config.cursor_height. Additionally, if the driver doesn't
> +	 * support modifiers, the framebuffer should have a linear layout.
> +	 *
> +	 * In addition to setting a plane type to cursor, drivers need to setup
> +	 * the &drm_crtc.cursor pointer for legacy IOCTLs. See
> +	 * drm_crtc_init_with_planes().
>  	 */
>  	DRM_PLANE_TYPE_CURSOR,
>  };
> -- 
> 2.29.2
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch