linux-kernel - [PATCH v2 RFC 07/10] drm/gem-fb-helper: Use actual bpp for size calculations

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Date:   Mon,  7 Mar 2022 21:52:42 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Sam Ravnborg <sam@...nborg.org>, Helge Deller <deller@....de>
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-m68k@...r.kernel.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH v2 RFC 07/10] drm/gem-fb-helper: Use actual bpp for size calculations

The AFBC helpers derive the number of bits per pixel from the deprecated
drm_format_info.cpp[] field, which does not take into account block
sizes.

Fix this by using the actual number of bits per pixel instead.

Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
---
RFC, as this code path was untested.

v2:
  - Replace FIXME by TODO comment.
---
 drivers/gpu/drm/drm_gem_framebuffer_helper.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
index 746fd8c738451247..e5b8443378d2294b 100644
--- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c
+++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
@@ -492,6 +492,8 @@ void drm_gem_fb_end_cpu_access(struct drm_framebuffer *fb, enum dma_data_directi
 }
 EXPORT_SYMBOL(drm_gem_fb_end_cpu_access);
 
+// TODO Drop this function and replace by drm_format_info_bpp() once all
+// DRM_FORMAT_* provide proper block info in drivers/gpu/drm/drm_fourcc.c
 static __u32 drm_gem_afbc_get_bpp(struct drm_device *dev,
 				  const struct drm_mode_fb_cmd2 *mode_cmd)
 {
@@ -499,11 +501,6 @@ static __u32 drm_gem_afbc_get_bpp(struct drm_device *dev,
 
 	info = drm_get_format_info(dev, mode_cmd);
 
-	/* use whatever a driver has set */
-	if (info->cpp[0])
-		return info->cpp[0] * 8;
-
-	/* guess otherwise */
 	switch (info->format) {
 	case DRM_FORMAT_YUV420_8BIT:
 		return 12;
@@ -512,11 +509,8 @@ static __u32 drm_gem_afbc_get_bpp(struct drm_device *dev,
 	case DRM_FORMAT_VUY101010:
 		return 30;
 	default:
-		break;
+		return drm_format_info_bpp(info, 0);
 	}
-
-	/* all attempts failed */
-	return 0;
 }
 
 static int drm_gem_afbc_min_size(struct drm_device *dev,
-- 
2.25.1