linux-kernel - [PATCH v5 1/6] drm/format-helper: Add drm_fb_xrgb8888_to_gray8

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Date:   Fri, 11 Feb 2022 15:33:53 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        linux-fbdev@...r.kernel.org, Sam Ravnborg <sam@...nborg.org>,
        Maxime Ripard <maxime@...no.tech>,
        dri-devel@...ts.freedesktop.org,
        Noralf Trønnes <noralf@...nnes.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>
Subject: [PATCH v5 1/6] drm/format-helper: Add drm_fb_xrgb8888_to_gray8_line()

Pull the per-line conversion logic into a separate helper function.

This will allow to do line-by-line conversion in other helpers that
convert to a gray8 format.

Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
---

Changes in v5:
- Add Thomas Zimmermann's Reviewed-by to patch #1.

Changes in v3:
- Add a drm_fb_xrgb8888_to_gray8_line() helper function (Thomas Zimmermann)

 drivers/gpu/drm/drm_format_helper.c | 31 ++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
index 0f28dd2bdd72..b981712623d3 100644
--- a/drivers/gpu/drm/drm_format_helper.c
+++ b/drivers/gpu/drm/drm_format_helper.c
@@ -464,6 +464,21 @@ void drm_fb_xrgb8888_to_xrgb2101010_toio(void __iomem *dst,
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_xrgb2101010_toio);
 
+static void drm_fb_xrgb8888_to_gray8_line(u8 *dst, const u32 *src, unsigned int pixels)
+{
+	unsigned int x;
+
+	for (x = 0; x < pixels; x++) {
+		u8 r = (*src & 0x00ff0000) >> 16;
+		u8 g = (*src & 0x0000ff00) >> 8;
+		u8 b =  *src & 0x000000ff;
+
+		/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
+		*dst++ = (3 * r + 6 * g + b) / 10;
+		src++;
+	}
+}
+
 /**
  * drm_fb_xrgb8888_to_gray8 - Convert XRGB8888 to grayscale
  * @dst: 8-bit grayscale destination buffer
@@ -484,8 +499,9 @@ EXPORT_SYMBOL(drm_fb_xrgb8888_to_xrgb2101010_toio);
 void drm_fb_xrgb8888_to_gray8(void *dst, unsigned int dst_pitch, const void *vaddr,
 			      const struct drm_framebuffer *fb, const struct drm_rect *clip)
 {
-	unsigned int len = (clip->x2 - clip->x1) * sizeof(u32);
-	unsigned int x, y;
+	unsigned int linepixels = clip->x2 - clip->x1;
+	unsigned int len = linepixels * sizeof(u32);
+	unsigned int y;
 	void *buf;
 	u8 *dst8;
 	u32 *src32;
@@ -508,16 +524,7 @@ void drm_fb_xrgb8888_to_gray8(void *dst, unsigned int dst_pitch, const void *vad
 	for (y = clip->y1; y < clip->y2; y++) {
 		dst8 = dst;
 		src32 = memcpy(buf, vaddr, len);
-		for (x = clip->x1; x < clip->x2; x++) {
-			u8 r = (*src32 & 0x00ff0000) >> 16;
-			u8 g = (*src32 & 0x0000ff00) >> 8;
-			u8 b =  *src32 & 0x000000ff;
-
-			/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
-			*dst8++ = (3 * r + 6 * g + b) / 10;
-			src32++;
-		}
-
+		drm_fb_xrgb8888_to_gray8_line(dst8, src32, linepixels);
 		vaddr += fb->pitches[0];
 		dst += dst_pitch;
 	}
-- 
2.34.1