Re: [PATCH 01/19] drm/fourcc: Add a function to tell if the format embeds alpha

[Ayan Halder <ayan.halder@arm.com>]

On Tue, Jan 09, 2018 at 02:28:33PM +0100, Maxime Ripard wrote:
> Hi Laurent,
> 
> On Tue, Jan 09, 2018 at 02:29:58PM +0200, Laurent Pinchart wrote:
> > On Tuesday, 9 January 2018 12:56:20 EET Maxime Ripard wrote:
> > > There's a bunch of drivers that duplicate the same function to know if a
> > > particular format embeds an alpha component or not.
> > > 
> > > Let's create a helper to avoid duplicating that logic.
> > > 
> > > Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
> > > Cc: Eric Anholt <eric@anholt.net>
> > > Cc: Inki Dae <inki.dae@samsung.com>
> > > Cc: Joonyoung Shim <jy0922.shim@samsung.com>
> > > Cc: Kyungmin Park <kyungmin.park@samsung.com>
> > > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > Cc: Mark Yao <mark.yao@rock-chips.com>
> > > Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
> > > Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> > > ---
> > >  drivers/gpu/drm/drm_fourcc.c | 43 +++++++++++++++++++++++++++++++++++++-
> > >  include/drm/drm_fourcc.h     |  1 +-
> > >  2 files changed, 44 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> > > index 9c0152df45ad..6e6227d6a46b 100644
> > > --- a/drivers/gpu/drm/drm_fourcc.c
> > > +++ b/drivers/gpu/drm/drm_fourcc.c
> > > @@ -348,3 +348,46 @@ int drm_format_plane_height(int height, uint32_t
> > > format, int plane) return height / info->vsub;
> > >  }
> > >  EXPORT_SYMBOL(drm_format_plane_height);
> > > +
> > > +/**
> > > + * drm_format_has_alpha - get whether the format embeds an alpha component
> > > + * @format: pixel format (DRM_FORMAT_*)
> > > + *
> > > + * Returns:
> > > + * true if the format embeds an alpha component, false otherwise.
> > > + */
> > > +bool drm_format_has_alpha(uint32_t format)
> > > +{
> > > +	switch (format) {
> > > +	case DRM_FORMAT_ARGB4444:
> > > +	case DRM_FORMAT_ABGR4444:
> > > +	case DRM_FORMAT_RGBA4444:
> > > +	case DRM_FORMAT_BGRA4444:
> > > +	case DRM_FORMAT_ARGB1555:
> > > +	case DRM_FORMAT_ABGR1555:
> > > +	case DRM_FORMAT_RGBA5551:
> > > +	case DRM_FORMAT_BGRA5551:
> > > +	case DRM_FORMAT_ARGB8888:
> > > +	case DRM_FORMAT_ABGR8888:
> > > +	case DRM_FORMAT_RGBA8888:
> > > +	case DRM_FORMAT_BGRA8888:
> > > +	case DRM_FORMAT_ARGB2101010:
> > > +	case DRM_FORMAT_ABGR2101010:
> > > +	case DRM_FORMAT_RGBA1010102:
> > > +	case DRM_FORMAT_BGRA1010102:
> > > +	case DRM_FORMAT_AYUV:
> > > +	case DRM_FORMAT_XRGB8888_A8:
> > > +	case DRM_FORMAT_XBGR8888_A8:
> > > +	case DRM_FORMAT_RGBX8888_A8:
> > > +	case DRM_FORMAT_BGRX8888_A8:
> > > +	case DRM_FORMAT_RGB888_A8:
> > > +	case DRM_FORMAT_BGR888_A8:
> > > +	case DRM_FORMAT_RGB565_A8:
> > > +	case DRM_FORMAT_BGR565_A8:
> > > +		return true;
> > > +
> > > +	default:
> > > +		return false;
> > > +	}
> > > +}
> > > +EXPORT_SYMBOL(drm_format_has_alpha);
> > 
> > How about adding the information to struct drm_format_info instead ? 
> > drm_format_has_alpha() could then be implemented as
> > 
> > bool drm_format_has_alpha(uint32_t format)
> > {
> > 	const struct drm_format_info *info;
> > 
> > 	info = drm_format_info(format);
> > 	return info ? info->has_alpha : false;
> > }
> 
> I considered it, and wasn't too sure about if adding more fields to
> drm_format_info was ok. I can definitely do it that way.\
Are you going to send an updated patch with the change mentioned here.
Or should I update my patch (https://patchwork.kernel.org/patch/10161023/)
and change the type of '.alpha' to boolean to denote if the color
format has an alpha channel or not.
> 
> > although drivers should really use the drm_framebuffer::format field directly 
> > in most cases, so the helper might not be needed at all.
> 
> The drivers converted in my serie shouldn't be too hard to convert to
> use drm_format_info directly, so that can be removed as well.
> 
> Maxime
> 
> -- 
> Maxime Ripard, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com



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