Re: [PATCH 1/4] drm: Centralize format information

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Tomi,

On Tuesday 07 Jun 2016 12:25:08 Tomi Valkeinen wrote:
> On 07/06/16 02:33, Laurent Pinchart wrote:
> > Various pieces of information about DRM formats (number of planes, color
> > depth, chroma subsampling, ...) are scattered across different helper
> > functions in the DRM core. Callers of those functions often need to
> > access more than a single parameter of the format, leading to
> > inefficiencies due to multiple lookups.
> > 
> > Centralize all format information in a data structure and create a
> > function to look up information based on the format 4CC.
> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > ---
> > 
> >  drivers/gpu/drm/drm_crtc.c | 83 +++++++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_crtc.h     | 21 ++++++++++++
> >  2 files changed, 104 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> > index 0e3cc66aa8b7..74b0c6dd80cd 100644
> > --- a/drivers/gpu/drm/drm_crtc.c
> > +++ b/drivers/gpu/drm/drm_crtc.c
> > @@ -5544,6 +5544,89 @@ int drm_mode_destroy_dumb_ioctl(struct drm_device
> > *dev,> 
> >  }
> >  
> >  /**
> > 
> > + * drm_format_info - information for a given format
> > + * @format: pixel format (DRM_FORMAT_*)
> > + *
> > + * Returns:
> > + * The instance of struct drm_format_info that describes the pixel
> > format, or + * NULL if the format is unsupported.
> > + */
> > +const struct drm_format_info *drm_format_info(u32 format)
> > +{
> > +	static const struct drm_format_info formats[] = {
> > +		{ DRM_FORMAT_C8, 8, 8, 1, { 1 }, 1, 1 },
> > +		{ DRM_FORMAT_RGB332, 8, 8, 1, { 1 }, 1, 1 },
> > +		{ DRM_FORMAT_BGR233, 8, 8, 1, { 1 }, 1, 1 },
> > +		{ DRM_FORMAT_XRGB4444, 12, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_XBGR4444, 12, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_RGBX4444, 12, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_BGRX4444, 12, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_ARGB4444, 12, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_ABGR4444, 12, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_RGBA4444, 12, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_BGRA4444, 12, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_XRGB1555, 15, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_XBGR1555, 15, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_RGBX5551, 15, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_BGRX5551, 15, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_ARGB1555, 15, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_ABGR1555, 15, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_RGBA5551, 15, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_BGRA5551, 15, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_RGB565, 16, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_BGR565, 16, 16, 1, { 2 }, 1, 1 },
> > +		{ DRM_FORMAT_RGB888, 24, 24, 1, { 3 }, 1, 1 },
> > +		{ DRM_FORMAT_BGR888, 24, 24, 1, { 3 }, 1, 1 },
> > +		{ DRM_FORMAT_XRGB8888, 24, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_XBGR8888, 24, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_RGBX8888, 24, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_BGRX8888, 24, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_XRGB2101010, 30, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_XBGR2101010, 30, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_RGBX1010102, 30, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_BGRX1010102, 30, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_ARGB2101010, 30, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_ABGR2101010, 30, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_RGBA1010102, 30, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_BGRA1010102, 30, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_ARGB8888, 32, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_ABGR8888, 32, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_RGBA8888, 32, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_BGRA8888, 32, 32, 1, { 4 }, 1, 1 },
> > +		{ DRM_FORMAT_YUV410, 0, 0, 3, { 1, 1, 1 }, 4, 4 },
> > +		{ DRM_FORMAT_YVU410, 0, 0, 3, { 1, 1, 1 }, 4, 4 },
> > +		{ DRM_FORMAT_YUV411, 0, 0, 3, { 1, 1, 1 }, 4, 1 },
> > +		{ DRM_FORMAT_YVU411, 0, 0, 3, { 1, 1, 1 }, 4, 1 },
> > +		{ DRM_FORMAT_YUV420, 0, 0, 3, { 1, 1, 1 }, 2, 2 },
> > +		{ DRM_FORMAT_YVU420, 0, 0, 3, { 1, 1, 1 }, 2, 2 },
> > +		{ DRM_FORMAT_YUV422, 0, 0, 3, { 1, 1, 1 }, 2, 1 },
> > +		{ DRM_FORMAT_YVU422, 0, 0, 3, { 1, 1, 1 }, 2, 1 },
> > +		{ DRM_FORMAT_YUV444, 0, 0, 3, { 1, 1, 1 }, 1, 1 },
> > +		{ DRM_FORMAT_YVU444, 0, 0, 3, { 1, 1, 1 }, 1, 1 },
> > +		{ DRM_FORMAT_NV12, 0, 0, 2, { 1, 2 }, 2, 2 },
> > +		{ DRM_FORMAT_NV21, 0, 0, 2, { 1, 2 }, 2, 2 },
> > +		{ DRM_FORMAT_NV16, 0, 0, 2, { 1, 2 }, 2, 1 },
> > +		{ DRM_FORMAT_NV61, 0, 0, 2, { 1, 2 }, 2, 1 },
> > +		{ DRM_FORMAT_NV24, 0, 0, 2, { 1, 2 }, 1, 1 },
> > +		{ DRM_FORMAT_NV42, 0, 0, 2, { 1, 2 }, 1, 1 },
> > +		{ DRM_FORMAT_YUYV, 0, 0, 1, { 2 }, 2, 1 },
> > +		{ DRM_FORMAT_YVYU, 0, 0, 1, { 2 }, 2, 1 },
> > +		{ DRM_FORMAT_UYVY, 0, 0, 1, { 2 }, 2, 1 },
> > +		{ DRM_FORMAT_VYUY, 0, 0, 1, { 2 }, 2, 1 },
> > +		{ DRM_FORMAT_AYUV, 0, 0, 1, { 4 }, 1, 1 },
> > +	};
> > +
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
> > +		if (formats[i].format == format)
> > +			return &formats[i];
> > +	}
> > +
> > +	return NULL;
> 
> After looking at the third patch, I wonder if it would make sense to
> give a warning here if the format was not found. In the third patch many
> of the helpers will quietly return a valid value for unknown modes.
> Which is what they do at the moment too, but is there ever a valid
> reason to do that without something being wrong?

We can't warn in this function due to its usage in framebuffer_check() that 
uses drm_format_info() to validate the format provided by userspace. However, 
I agree that all other call sites should not pass an unsupported format, that 
would be a bug in the caller.

I can rename the function to __drm_format_info(), call that in 
framebuffer_check(), and create a drm_format_info() wrapper with a WARN_ON if 
the format isn't found. Would you prefer that ?

-- 
Regards,

Laurent Pinchart

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