[PATCH 3/8] drm/fourcc: Add drm_format_info_bpp() helper

[Geert Uytterhoeven <geert@linux-m68k.org>]

Add a helper to retrieve the actual number of bits per pixel for a
plane, taking into account the number of characters and pixels per
block for tiled formats.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 drivers/gpu/drm/drm_fourcc.c | 19 +++++++++++++++++++
 include/drm/drm_fourcc.h     |  1 +
 2 files changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
index 60ce63d728b8e308..5c77ce10f53e3a64 100644
--- a/drivers/gpu/drm/drm_fourcc.c
+++ b/drivers/gpu/drm/drm_fourcc.c
@@ -388,6 +388,25 @@ unsigned int drm_format_info_block_height(const struct drm_format_info *info,
 }
 EXPORT_SYMBOL(drm_format_info_block_height);
 
+/**
+ * drm_format_info_bpp - number of bits per pixel
+ * @info: pixel format info
+ * @plane: plane index
+ *
+ * Returns:
+ * The actual number of bits per pixel, depending on the plane index.
+ */
+unsigned int drm_format_info_bpp(const struct drm_format_info *info, int plane)
+{
+	if (!info || plane < 0 || plane >= info->num_planes)
+		return 0;
+
+	return info->char_per_block[plane] * 8 /
+	       (drm_format_info_block_width(info, plane) *
+		drm_format_info_block_height(info, plane));
+}
+EXPORT_SYMBOL(drm_format_info_bpp);
+
 /**
  * drm_format_info_min_pitch - computes the minimum required pitch in bytes
  * @info: pixel format info
diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h
index 22aa64d07c7905e2..3800a7ad7f0cda7a 100644
--- a/include/drm/drm_fourcc.h
+++ b/include/drm/drm_fourcc.h
@@ -313,6 +313,7 @@ unsigned int drm_format_info_block_width(const struct drm_format_info *info,
 					 int plane);
 unsigned int drm_format_info_block_height(const struct drm_format_info *info,
 					  int plane);
+unsigned int drm_format_info_bpp(const struct drm_format_info *info, int plane);
 uint64_t drm_format_info_min_pitch(const struct drm_format_info *info,
 				   int plane, unsigned int buffer_width);
 
-- 
2.25.1