drm/vkms: Create helper macro for YUV formats

The callback functions for line conversion are almost identical for
semi-planar formats. The generic READ_LINE_YUV_SEMIPLANAR macro
generate all the required boilerplate to process a line from a
semi-planar format.

Reviewed-by: Maíra Canal <mcanal@igalia.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Link: https://lore.kernel.org/r/20250703-b4-new-color-formats-v7-7-15fd8fd2e15c@bootlin.com
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>

Author: Fomys

drivers/gpu/drm/vkms/vkms_formats.c

@@ -479,35 +479,56 @@ READ_LINE(R8_read_line, px, u8, argb_u16_from_gray8, *px)
  * - Convert YUV and YVU with the same function (a column swap is needed when setting up
  * plane->conversion_matrix)
  */
-static void semi_planar_yuv_read_line(const struct vkms_plane_state *plane, int x_start,
-				      int y_start, enum pixel_read_direction direction, int count,
-				      struct pixel_argb_u16 out_pixel[])
-{
-	u8 *y_plane;
-	u8 *uv_plane;
-
-	packed_pixels_addr_1x1(plane->frame_info, x_start, y_start, 0,
-			       &y_plane);
-	packed_pixels_addr_1x1(plane->frame_info,
-			       x_start / plane->frame_info->fb->format->hsub,
-			       y_start / plane->frame_info->fb->format->vsub, 1,
-			       &uv_plane);
-	int step_y = get_block_step_bytes(plane->frame_info->fb, direction, 0);
-	int step_uv = get_block_step_bytes(plane->frame_info->fb, direction, 1);
-	int subsampling = get_subsampling(plane->frame_info->fb->format, direction);
-	int subsampling_offset = get_subsampling_offset(direction, x_start, y_start);
-	const struct conversion_matrix *conversion_matrix = &plane->conversion_matrix;
 
-	for (int i = 0; i < count; i++) {
-		*out_pixel = argb_u16_from_yuv161616(conversion_matrix, y_plane[0] * 257,
-						     uv_plane[0] * 257, uv_plane[1] * 257);
-		out_pixel += 1;
-		y_plane += step_y;
-		if ((i + subsampling_offset + 1) % subsampling == 0)
-			uv_plane += step_uv;
-	}
+/**
+ * READ_LINE_YUV_SEMIPLANAR() - Generic generator for a read_line function which can be used for yuv
+ * formats with two planes and block_w == block_h == 1.
+ *
+ * @function_name: Function name to generate
+ * @pixel_1_name: temporary pixel name for the first plane used in the @__VA_ARGS__ parameters
+ * @pixel_2_name: temporary pixel name for the second plane used in the @__VA_ARGS__ parameters
+ * @pixel_1_type: Used to specify the type you want to cast the pixel pointer on the plane 1
+ * @pixel_2_type: Used to specify the type you want to cast the pixel pointer on the plane 2
+ * @callback: Callback to call for each pixels. This function should take
+ *            (struct conversion_matrix*, @__VA_ARGS__) as parameter and return a pixel_argb_u16
+ * __VA_ARGS__: Argument to pass inside the callback. You can use @pixel_1_name and @pixel_2_name
+ *               to access current pixel values
+ */
+#define READ_LINE_YUV_SEMIPLANAR(function_name, pixel_1_name, pixel_2_name, pixel_1_type,	\
+				 pixel_2_type, callback, ...)					\
+static void function_name(const struct vkms_plane_state *plane, int x_start,			\
+		 int y_start, enum pixel_read_direction direction, int count,			\
+		 struct pixel_argb_u16 out_pixel[])						\
+{												\
+	u8 *plane_1;										\
+	u8 *plane_2;										\
+												\
+	packed_pixels_addr_1x1(plane->frame_info, x_start, y_start, 0,				\
+			       &plane_1);							\
+	packed_pixels_addr_1x1(plane->frame_info,						\
+			       x_start / plane->frame_info->fb->format->hsub,			\
+			       y_start / plane->frame_info->fb->format->vsub, 1,		\
+			       &plane_2);							\
+	int step_1 = get_block_step_bytes(plane->frame_info->fb, direction, 0);			\
+	int step_2 = get_block_step_bytes(plane->frame_info->fb, direction, 1);			\
+	int subsampling = get_subsampling(plane->frame_info->fb->format, direction);		\
+	int subsampling_offset = get_subsampling_offset(direction, x_start, y_start);		\
+	const struct conversion_matrix *conversion_matrix = &plane->conversion_matrix;		\
+												\
+	for (int i = 0; i < count; i++) {							\
+		pixel_1_type *(pixel_1_name) = (pixel_1_type *)plane_1;				\
+		pixel_2_type *(pixel_2_name) = (pixel_2_type *)plane_2;				\
+		*out_pixel = (callback)(conversion_matrix, __VA_ARGS__);			\
+		out_pixel += 1;									\
+		plane_1 += step_1;								\
+		if ((i + subsampling_offset + 1) % subsampling == 0)				\
+			plane_2 += step_2;							\
+	}											\
 }
 
+READ_LINE_YUV_SEMIPLANAR(YUV888_semiplanar_read_line, y, uv, u8, u8, argb_u16_from_yuv161616,
+			 y[0] * 257, uv[0] * 257, uv[1] * 257)
+
 /*
  * This callback can be used for YUV format where each color component is
  * stored in a different plane (often called planar formats). It will
@@ -703,7 +724,7 @@ pixel_read_line_t get_pixel_read_line_function(u32 format)
 	case DRM_FORMAT_NV21:
 	case DRM_FORMAT_NV61:
 	case DRM_FORMAT_NV42:
-		return &semi_planar_yuv_read_line;
+		return &YUV888_semiplanar_read_line;
 	case DRM_FORMAT_YUV420:
 	case DRM_FORMAT_YUV422:
 	case DRM_FORMAT_YUV444: