drm/fourcc: Add format info helpers for checking YUV sub-sampling

Display engine drivers often need to distinguish between different types of
YUV sub-sampling. This introduces helpers to check for common sub-sampling
ratios in their commonly-used denomination from the DRM format info.
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Reviewed-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190118145133.21281-3-paul.kocialkowski@bootlin.com

include/drm/drm_fourcc.h

@@ -185,6 +185,81 @@ drm_format_info_is_yuv_planar(const struct drm_format_info *info)
 	return info->is_yuv && info->num_planes == 3;
 }
 
+/**
+ * drm_format_info_is_yuv_sampling_410 - check that the format info matches a
+ * YUV format with 4:1:0 sub-sampling
+ * @info: format info
+ *
+ * Returns:
+ * A boolean indicating whether the format info matches a YUV format with 4:1:0
+ * sub-sampling.
+ */
+static inline bool
+drm_format_info_is_yuv_sampling_410(const struct drm_format_info *info)
+{
+	return info->is_yuv && info->hsub == 4 && info->vsub == 4;
+}
+
+/**
+ * drm_format_info_is_yuv_sampling_411 - check that the format info matches a
+ * YUV format with 4:1:1 sub-sampling
+ * @info: format info
+ *
+ * Returns:
+ * A boolean indicating whether the format info matches a YUV format with 4:1:1
+ * sub-sampling.
+ */
+static inline bool
+drm_format_info_is_yuv_sampling_411(const struct drm_format_info *info)
+{
+	return info->is_yuv && info->hsub == 4 && info->vsub == 1;
+}
+
+/**
+ * drm_format_info_is_yuv_sampling_420 - check that the format info matches a
+ * YUV format with 4:2:0 sub-sampling
+ * @info: format info
+ *
+ * Returns:
+ * A boolean indicating whether the format info matches a YUV format with 4:2:0
+ * sub-sampling.
+ */
+static inline bool
+drm_format_info_is_yuv_sampling_420(const struct drm_format_info *info)
+{
+	return info->is_yuv && info->hsub == 2 && info->vsub == 2;
+}
+
+/**
+ * drm_format_info_is_yuv_sampling_422 - check that the format info matches a
+ * YUV format with 4:2:2 sub-sampling
+ * @info: format info
+ *
+ * Returns:
+ * A boolean indicating whether the format info matches a YUV format with 4:2:2
+ * sub-sampling.
+ */
+static inline bool
+drm_format_info_is_yuv_sampling_422(const struct drm_format_info *info)
+{
+	return info->is_yuv && info->hsub == 2 && info->vsub == 1;
+}
+
+/**
+ * drm_format_info_is_yuv_sampling_444 - check that the format info matches a
+ * YUV format with 4:4:4 sub-sampling
+ * @info: format info
+ *
+ * Returns:
+ * A boolean indicating whether the format info matches a YUV format with 4:4:4
+ * sub-sampling.
+ */
+static inline bool
+drm_format_info_is_yuv_sampling_444(const struct drm_format_info *info)
+{
+	return info->is_yuv && info->hsub == 1 && info->vsub == 1;
+}
+
 const struct drm_format_info *__drm_format_info(u32 format);
 const struct drm_format_info *drm_format_info(u32 format);
 const struct drm_format_info *