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

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Date:   Tue, 9 Jan 2018 14:28:33 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     dri-devel@...ts.freedesktop.org, Chen-Yu Tsai <wens@...e.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        linux-kernel@...r.kernel.org,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Mark Yao <mark.yao@...k-chips.com>,
        linux-arm-kernel@...ts.infradead.org, thomas@...sch.nl
Subject: Re: [PATCH 01/19] drm/fourcc: Add a function to tell if the format
 embeds alpha

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@...e-electrons.com>
> > Cc: Eric Anholt <eric@...olt.net>
> > Cc: Inki Dae <inki.dae@...sung.com>
> > Cc: Joonyoung Shim <jy0922.shim@...sung.com>
> > Cc: Kyungmin Park <kyungmin.park@...sung.com>
> > Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > Cc: Mark Yao <mark.yao@...k-chips.com>
> > Cc: Seung-Woo Kim <sw0312.kim@...sung.com>
> > Signed-off-by: Maxime Ripard <maxime.ripard@...e-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.

> 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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