drm: Add drm_format_plane_cpp() utility function

This function returns the bytes per pixel value based on the pixel
format and plane index.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_crtc.c

@@ -3498,3 +3498,48 @@ int drm_format_num_planes(uint32_t format)
 	}
 }
 EXPORT_SYMBOL(drm_format_num_planes);
+
+/**
+ * drm_format_plane_cpp - determine the bytes per pixel value
+ * @format: pixel format (DRM_FORMAT_*)
+ * @plane: plane index
+ *
+ * RETURNS:
+ * The bytes per pixel value for the specified plane.
+ */
+int drm_format_plane_cpp(uint32_t format, int plane)
+{
+	unsigned int depth;
+	int bpp;
+
+	if (plane >= drm_format_num_planes(format))
+		return 0;
+
+	switch (format) {
+	case DRM_FORMAT_YUYV:
+	case DRM_FORMAT_YVYU:
+	case DRM_FORMAT_UYVY:
+	case DRM_FORMAT_VYUY:
+		return 2;
+	case DRM_FORMAT_NV12:
+	case DRM_FORMAT_NV21:
+	case DRM_FORMAT_NV16:
+	case DRM_FORMAT_NV61:
+		return plane ? 2 : 1;
+	case DRM_FORMAT_YUV410:
+	case DRM_FORMAT_YVU410:
+	case DRM_FORMAT_YUV411:
+	case DRM_FORMAT_YVU411:
+	case DRM_FORMAT_YUV420:
+	case DRM_FORMAT_YVU420:
+	case DRM_FORMAT_YUV422:
+	case DRM_FORMAT_YVU422:
+	case DRM_FORMAT_YUV444:
+	case DRM_FORMAT_YVU444:
+		return 1;
+	default:
+		drm_fb_get_bpp_depth(format, &depth, &bpp);
+		return bpp >> 3;
+	}
+}
+EXPORT_SYMBOL(drm_format_plane_cpp);

include/drm/drm_crtc.h

@@ -1027,5 +1027,6 @@ extern int drm_mode_destroy_dumb_ioctl(struct drm_device *dev,
 extern void drm_fb_get_bpp_depth(uint32_t format, unsigned int *depth,
 				 int *bpp);
 extern int drm_format_num_planes(uint32_t format);
+extern int drm_format_plane_cpp(uint32_t format, int plane);
 
 #endif /* __DRM_CRTC_H__ */