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From:   Geert Uytterhoeven <geert@linux-m68k.org>
To:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>
Cc:     dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
        linux-m68k@vger.kernel.org, linux-kernel@vger.kernel.org,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Javier Martinez Canillas <javierm@redhat.com>
Subject: [PATCH v3 08/10] drm/fourcc: Clarify the meaning of single-channel "red"
Date:   Fri,  8 Jul 2022 20:20:53 +0200
Message-Id: <31d1792f26707a7270347e9916b4103470d2b192.1657294931.git.geert@linux-m68k.org>
In-Reply-To: <cover.1657294931.git.geert@linux-m68k.org>
References: <cover.1657294931.git.geert@linux-m68k.org>
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Traditionally, the first channel has been called the "red" channel, but
the fourcc values for single-channel "red" formats can also be used for
other single-channel formats with a direct relationship between channel
value and brightness, like grayscale.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
---
v3:
  - Add Reviewed-by,
  - Replace light-on-dark by direct relationship between channel value
    and brightness,

v2:
  - New.
---
 include/uapi/drm/drm_fourcc.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
index e18de6f258302673..dff5072fccaaf65c 100644
--- a/include/uapi/drm/drm_fourcc.h
+++ b/include/uapi/drm/drm_fourcc.h
@@ -104,16 +104,16 @@ extern "C" {
 #define DRM_FORMAT_C4		fourcc_code('C', '4', ' ', ' ') /* [7:0] C0:C1 4:4 two pixels/byte */
 #define DRM_FORMAT_C8		fourcc_code('C', '8', ' ', ' ') /* [7:0] C */
 
-/* 8 bpp Red */
+/* 8 bpp Red (direct relationship between channel value and brightness) */
 #define DRM_FORMAT_R8		fourcc_code('R', '8', ' ', ' ') /* [7:0] R */
 
-/* 10 bpp Red */
+/* 10 bpp Red (direct relationship between channel value and brightness) */
 #define DRM_FORMAT_R10		fourcc_code('R', '1', '0', ' ') /* [15:0] x:R 6:10 little endian */
 
-/* 12 bpp Red */
+/* 12 bpp Red (direct relationship between channel value and brightness) */
 #define DRM_FORMAT_R12		fourcc_code('R', '1', '2', ' ') /* [15:0] x:R 4:12 little endian */
 
-/* 16 bpp Red */
+/* 16 bpp Red (direct relationship between channel value and brightness) */
 #define DRM_FORMAT_R16		fourcc_code('R', '1', '6', ' ') /* [15:0] R little endian */
 
 /* 16 bpp RG */
-- 
2.25.1