Re: [Intel-gfx] [PATCH 6/9] drm: Add drm_rotation_simplify()

[Imre Deak <imre.deak@intel.com>]

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On Mon, 2013-09-30 at 17:44 +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> drm_rotation_simplify() can be used to eliminate unsupported rotation
> flags. It will check if any unsupported flags are present, and if so
> it will modify the rotation to an alternate form by adding 180 degrees
> to rotation angle, and flipping the reflect x and y bits. The hope is
> that this identity transform will eliminate the unsupported flags.
> 
> Of course that might not result in any more supported rotation, so
> the caller is still responsible for checking the result afterwards.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_crtc.c | 30 ++++++++++++++++++++++++++++++
>  include/drm/drm_crtc.h     |  2 ++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 0218681..665b807 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -3976,6 +3976,36 @@ int drm_format_vert_chroma_subsampling(uint32_t format)
>  EXPORT_SYMBOL(drm_format_vert_chroma_subsampling);
>  
>  /**
> + * drm_rotation_simplify() - Try to simplify the rotation
> + * @rotation: Rotation to be simplified
> + * @supported_rotations: Supported rotations
> + *
> + * Attempt to simplify the rotation to a form that is supported.
> + * Eg. if the hardware supports everything except DRM_REFLECT_X
> + * one could call this function like this:
> + *
> + * drm_rotation_simplify(rotation, BIT(DRM_ROTATE_0) |
> + *                       BIT(DRM_ROTATE_90) | BIT(DRM_ROTATE_180) |
> + *                       BIT(DRM_ROTATE_270) | BIT(DRM_REFLECT_Y));
> + *
> + * to eliminate the DRM_ROTATE_X flag. Depending on what kind of
                      ^ DRM_REFLECT_X

You don't use this function in your patchset, though
intel_plane_set_property() could use it by accepting REFLECT_X|REFLECT_Y
too. But it does what it says, so I'm also ok if you leave it unused for
now.

--Imre

> + * transforms the hardware supports, this function may not
> + * be able to produce a supported transform, so the caller should
> + * check the result afterwards.
> + */
> +unsigned int drm_rotation_simplify(unsigned int rotation,
> +				   unsigned int supported_rotations)
> +{
> +	if (rotation & ~supported_rotations) {
> +		rotation ^= BIT(DRM_REFLECT_X) | BIT(DRM_REFLECT_Y);
> +		rotation = (rotation & ~0xf) | BIT((ffs(rotation & 0xf) + 1) % 4);
> +	}
> +
> +	return rotation;
> +}
> +EXPORT_SYMBOL(drm_rotation_simplify);
> +
> +/**
>   * drm_mode_config_init - initialize DRM mode_configuration structure
>   * @dev: DRM device
>   *
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index d25ba84..b97b367 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1154,5 +1154,7 @@ extern int drm_format_vert_chroma_subsampling(uint32_t format);
>  extern const char *drm_get_format_name(uint32_t format);
>  extern struct drm_property *drm_mode_create_rotation_property(struct drm_device *dev,
>  							      unsigned int supported_rotations);
> +extern unsigned int drm_rotation_simplify(unsigned int rotation,
> +					  unsigned int supported_rotations);
>  
>  #endif /* __DRM_CRTC_H__ */


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