On Fri, Jul 08, 2022 at 08:20:46PM +0200, Geert Uytterhoeven wrote:
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@xxxxxxxxxxxxxx>
Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
---
v3:
- Add Reviewed-by,
v2:
- Move up.
---
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 07741b678798b0f1..cf48ea0b2cb70ba8 100644
--- a/drivers/gpu/drm/drm_fourcc.c
+++ b/drivers/gpu/drm/drm_fourcc.c
@@ -370,6 +370,25 @@ 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));
Do we really needs this for blocky formats where this is potentially
ill-defined? I think if there's no need then this should also return 0
when block_width/height != 1, it doesn't make much sense to compute bpp
when it's not really bits per _pixel_.
Minimally this needs to check whether the division actually makes sense or
whether there's a reminder, and if there's reminder, then fail. But that
feels like a bad hack and I think we should avoid it if it's not
absolutely necessary.
Otherwise lgtm.
-Daniel
+}
+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
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
