Re: [PATCH 1/2] drm/fb-helper: Make fbdev inherit the crtc's rotation

[Bastien Nocera <hadess@hadess.net>]

On Sun, 2017-04-23 at 18:11 +0200, Hans de Goede wrote:
> From: Ville Syrjala <ville.syrjala@linux.intel.com>
> 
> If a connector added through drm_fb_helper_add_one_connector() has
> a crtc attached and that crtc has a rotation configured make the
> fbdev inherit the crtc's rotation.
> 
> This is useful on e.g. some tablets which have their lcd panel
> mounted
> upside down, which before this commit would result in the kernel boot
> messages switching from being shown the right way up in efifb to
> being
> shown upside down as soon as a native kms driver loads.
> 
> BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=94894
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> [hdegoede@redhat.com: Split the drm/fb-helper bits out of Ville's
>  "drm/fb-helper: Inherit rotation wip" patch]
> Tested-by: Hans de Goede <hdegoede@redhat.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/gpu/drm/drm_fb_helper.c | 51
> ++++++++++++++++++++++++++++++++++++++---
>  include/drm/drm_fb_helper.h     |  2 ++
>  2 files changed, 50 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c
> b/drivers/gpu/drm/drm_fb_helper.c
> index 324a688..c97e00ab 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -159,6 +159,8 @@ int drm_fb_helper_add_one_connector(struct
> drm_fb_helper *fb_helper, struct drm_
>  {
>  	struct drm_fb_helper_connector **temp;
>  	struct drm_fb_helper_connector *fb_helper_connector;
> +	struct drm_crtc *crtc = connector->encoder ?
> +				connector->encoder->crtc : NULL;
>  
>  	if (!drm_fbdev_emulation)
>  		return 0;
> @@ -180,6 +182,11 @@ int drm_fb_helper_add_one_connector(struct
> drm_fb_helper *fb_helper, struct drm_
>  
>  	drm_connector_reference(connector);
>  	fb_helper_connector->connector = connector;
> +	if (crtc && crtc->primary->state)
> +		fb_helper_connector->rotation = crtc->primary-
> >state->rotation;
> +	if (!fb_helper_connector->rotation)
> +		fb_helper_connector->rotation = DRM_ROTATE_0;

That's equivalent to:
if (fb_helper_connector->rotation = DRM_ROTATE_0)
   fb_helper_connector->rotation = DRM_ROTATE_0;

Maybe:
if (crtc && crtc->primary->state)
   ...
else
   ...->rotation = DRM_ROTATE_0;
would be clearer? Or simply omit it if the connector is zero'ed.   

<snip>
> diff --git a/include/drm/drm_fb_helper.h
> b/include/drm/drm_fb_helper.h
> index 6f5aceb..19fc313 100644
> --- a/include/drm/drm_fb_helper.h
> +++ b/include/drm/drm_fb_helper.h
> @@ -48,6 +48,7 @@ struct drm_fb_helper_crtc {
>  	struct drm_mode_set mode_set;
>  	struct drm_display_mode *desired_mode;
>  	int x, y;
> +	uint8_t rotation;
>  };
>  
>  /**
> @@ -159,6 +160,7 @@ struct drm_fb_helper_funcs {
>  
>  struct drm_fb_helper_connector {
>  	struct drm_connector *connector;
> +	uint8_t rotation;

In both those cases, I'd add a mention of the type of enum/mask etc.
for the rotation, for example:
uint8_t rotation; /* DRM_ROTATE_* */
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