[PATCH v5 07/16] drm/vkms: Update pixels accessor to support packed and multi-plane formats.

[Louis Chauvet]

Introduce the usage of block_h/block_w to compute the offset and the
pointer of a pixel. The previous implementation was specialized for
planes with block_h == block_w == 1. To avoid confusion and allow easier
implementation of tiled formats. It also remove the usage of the
deprecated format field `cpp`.

Introduce the plane_index parameter to get an offset/pointer on a
different plane.

Signed-off-by: Louis Chauvet <louis.chauvet at bootlin.com>
---
 drivers/gpu/drm/vkms/vkms_formats.c | 76 +++++++++++++++++++++++++------------
 1 file changed, 52 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
index b2f8dfc26c35..649d75d05b1f 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.c
+++ b/drivers/gpu/drm/vkms/vkms_formats.c
@@ -10,23 +10,43 @@
 #include "vkms_formats.h"
 
 /**
- * pixel_offset() - Get the offset of the pixel at coordinates x/y in the first plane
+ * packed_pixels_offset() - Get the offset of the block containing the pixel at coordinates x/y
  *
  * @frame_info: Buffer metadata
  * @x: The x coordinate of the wanted pixel in the buffer
  * @y: The y coordinate of the wanted pixel in the buffer
+ * @plane_index: The index of the plane to use
+ * @offset: The returned offset inside the buffer of the block
+ * @rem_x, at rem_y: The returned coordinate of the requested pixel in the block
  *
- * The caller must ensure that the framebuffer associated with this request uses a pixel format
- * where block_h == block_w == 1.
- * If this requirement is not fulfilled, the resulting offset can point to an other pixel or
- * outside of the buffer.
+ * As some pixel formats store multiple pixels in a block (DRM_FORMAT_R* for example), some
+ * pixels are not individually addressable. This function return 3 values: the offset of the
+ * whole block, and the coordinate of the requested pixel inside this block.
+ * For example, if the format is DRM_FORMAT_R1 and the requested coordinate is 13,5, the offset
+ * will point to the byte 5*pitches + 13/8 (second byte of the 5th line), and the rem_x/rem_y
+ * coordinates will be (13 % 8, 5 % 1) = (5, 0)
+ *
+ * With this function, the caller just have to extract the correct pixel from the block.
  */
-static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int y)
+static void packed_pixels_offset(const struct vkms_frame_info *frame_info, int x, int y,
+				 int plane_index, int *offset, int *rem_x, int *rem_y)
 {
 	struct drm_framebuffer *fb = frame_info->fb;
+	const struct drm_format_info *format = frame_info->fb->format;
+	/* Directly using x and y to multiply pitches and format->ccp is not sufficient because
+	 * in some formats a block can represent multiple pixels.
+	 *
+	 * Dividing x and y by the block size allows to extract the correct offset of the block
+	 * containing the pixel.
+	 */
 
-	return fb->offsets[0] + (y * fb->pitches[0])
-			      + (x * fb->format->cpp[0]);
+	int block_x = x / drm_format_info_block_width(format, plane_index);
+	int block_y = y / drm_format_info_block_height(format, plane_index);
+	*rem_x = x % drm_format_info_block_width(format, plane_index);
+	*rem_y = x % drm_format_info_block_height(format, plane_index);
+	*offset = fb->offsets[plane_index] +
+		  block_y * fb->pitches[plane_index] +
+		  block_x * format->char_per_block[plane_index];
 }
 
 /**
@@ -36,30 +56,35 @@ static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int
  * @frame_info: Buffer metadata
  * @x: The x(width) coordinate inside the plane
  * @y: The y(height) coordinate inside the plane
+ * @plane_index: The index of the plane
+ * @addr: The returned pointer
+ * @rem_x, at rem_y: The returned coordinate of the requested pixel in the block
  *
- * Takes the information stored in the frame_info, a pair of coordinates, and
- * returns the address of the first color channel.
- * This function assumes the channels are packed together, i.e. a color channel
- * comes immediately after another in the memory. And therefore, this function
- * doesn't work for YUV with chroma subsampling (e.g. YUV420 and NV21).
+ * Takes the information stored in the frame_info, a pair of coordinates, and returns the address
+ * of the block containing this pixel and the pixel position inside this block.
  *
- * The caller must ensure that the framebuffer associated with this request uses a pixel format
- * where block_h == block_w == 1, otherwise the returned pointer can be outside the buffer.
+ * See @packed_pixel_offset for details about rem_x/rem_y behavior.
  */
-static void *packed_pixels_addr(const struct vkms_frame_info *frame_info,
-				int x, int y)
+static void packed_pixels_addr(const struct vkms_frame_info *frame_info,
+			       int x, int y, int plane_index, u8 **addr, int *rem_x,
+			       int *rem_y)
 {
-	size_t offset = pixel_offset(frame_info, x, y);
+	int offset;
 
-	return (u8 *)frame_info->map[0].vaddr + offset;
+	packed_pixels_offset(frame_info, x, y, plane_index, &offset, rem_x, rem_y);
+	*addr = (u8 *)frame_info->map[0].vaddr + offset;
 }
 
-static void *get_packed_src_addr(const struct vkms_frame_info *frame_info, int y)
+static void *get_packed_src_addr(const struct vkms_frame_info *frame_info, int y,
+				 int plane_index)
 {
 	int x_src = frame_info->src.x1 >> 16;
 	int y_src = y - frame_info->rotated.y1 + (frame_info->src.y1 >> 16);
+	u8 *addr;
+	int rem_x, rem_y;
 
-	return packed_pixels_addr(frame_info, x_src, y_src);
+	packed_pixels_addr(frame_info, x_src, y_src, plane_index, &addr, &rem_x, &rem_y);
+	return addr;
 }
 
 static int get_x_position(const struct vkms_frame_info *frame_info, int limit, int x)
@@ -168,14 +193,14 @@ void vkms_compose_row(struct line_buffer *stage_buffer, struct vkms_plane_state
 {
 	struct pixel_argb_u16 *out_pixels = stage_buffer->pixels;
 	struct vkms_frame_info *frame_info = plane->frame_info;
-	u8 *src_pixels = get_packed_src_addr(frame_info, y);
+	u8 *src_pixels = get_packed_src_addr(frame_info, y, 0);
 	int limit = min_t(size_t, drm_rect_width(&frame_info->dst), stage_buffer->n_pixels);
 
 	for (size_t x = 0; x < limit; x++, src_pixels += frame_info->fb->format->cpp[0]) {
 		int x_pos = get_x_position(frame_info, limit, x);
 
 		if (drm_rotation_90_or_270(frame_info->rotation))
-			src_pixels = get_packed_src_addr(frame_info, x + frame_info->rotated.y1)
+			src_pixels = get_packed_src_addr(frame_info, x + frame_info->rotated.y1, 0)
 				+ frame_info->fb->format->cpp[0] * y;
 
 		plane->pixel_read(src_pixels, &out_pixels[x_pos]);
@@ -276,7 +301,10 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
 {
 	struct vkms_frame_info *frame_info = &wb->wb_frame_info;
 	int x_dst = frame_info->dst.x1;
-	u8 *dst_pixels = packed_pixels_addr(frame_info, x_dst, y);
+	u8 *dst_pixels;
+	int rem_x, rem_y;
+
+	packed_pixels_addr(frame_info, x_dst, y, 0, &dst_pixels, &rem_x, &rem_y);
 	struct pixel_argb_u16 *in_pixels = src_buffer->pixels;
 	int x_limit = min_t(size_t, drm_rect_width(&frame_info->dst), src_buffer->n_pixels);
 

-- 
2.43.0