drm/vkms: Introduce pixel_read_direction enum

The pixel_read_direction enum is useful to describe the reading direction
in a plane. It avoids using the rotation property of DRM, which not
practical to know the direction of reading.
This patch also introduce two helpers, one to compute the
pixel_read_direction from the DRM rotation property, and one to compute
the step, in byte, between two successive pixel in a specific direction.

Acked-by: Maíra Canal <mairacanal@riseup.net>
Reviewed-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241118-yuv-v14-7-2dbc2f1e222c@bootlin.com
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>

diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
index e406ab4b14fd4288816565b3cabec93cea5834ae..c2181afa41216c38a52656bfb49e8210c69a9e58 100644 (file)
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -159,6 +159,50 @@ static void apply_lut(const struct vkms_crtc_state *crtc_state, struct line_buff
        }
 }
 
+/**
+ * direction_for_rotation() - Get the correct reading direction for a given rotation
+ *
+ * @rotation: Rotation to analyze. It correspond the field @frame_info.rotation.
+ *
+ * This function will use the @rotation setting of a source plane to compute the reading
+ * direction in this plane which correspond to a "left to right writing" in the CRTC.
+ * For example, if the buffer is reflected on X axis, the pixel must be read from right to left
+ * to be written from left to right on the CRTC.
+ */
+static enum pixel_read_direction direction_for_rotation(unsigned int rotation)
+{
+       struct drm_rect tmp_a, tmp_b;
+       int x, y;
+
+       /*
+        * Points A and B are depicted as zero-size rectangles on the CRTC.
+        * The CRTC writing direction is from A to B. The plane reading direction
+        * is discovered by inverse-transforming A and B.
+        * The reading direction is computed by rotating the vector AB (top-left to top-right) in a
+        * 1x1 square.
+        */
+
+       tmp_a = DRM_RECT_INIT(0, 0, 0, 0);
+       tmp_b = DRM_RECT_INIT(1, 0, 0, 0);
+       drm_rect_rotate_inv(&tmp_a, 1, 1, rotation);
+       drm_rect_rotate_inv(&tmp_b, 1, 1, rotation);
+
+       x = tmp_b.x1 - tmp_a.x1;
+       y = tmp_b.y1 - tmp_a.y1;
+
+       if (x == 1 && y == 0)
+               return READ_LEFT_TO_RIGHT;
+       else if (x == -1 && y == 0)
+               return READ_RIGHT_TO_LEFT;
+       else if (y == 1 && x == 0)
+               return READ_TOP_TO_BOTTOM;
+       else if (y == -1 && x == 0)
+               return READ_BOTTOM_TO_TOP;
+
+       WARN_ONCE(true, "The inverse of the rotation gives an incorrect direction.");
+       return READ_LEFT_TO_RIGHT;
+}
+
 /**
  * blend - blend the pixels from all planes and compute crc
  * @wb: The writeback frame buffer metadata

diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index 86af4606c1ee591294adc9655babfa91a78a4423..272d7215071b021fb4a3826e5f2d057bff958e64 100644 (file)
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -69,6 +69,17 @@ struct vkms_writeback_job {
        pixel_write_t pixel_write;
 };
 
+/**
+ * enum pixel_read_direction - Enum used internally by VKMS to represent a reading direction in a
+ * plane.
+ */
+enum pixel_read_direction {
+       READ_BOTTOM_TO_TOP,
+       READ_TOP_TO_BOTTOM,
+       READ_RIGHT_TO_LEFT,
+       READ_LEFT_TO_RIGHT
+};
+
 /**
  * typedef pixel_read_t - These functions are used to read a pixel in the source frame,
  * convert it to `struct pixel_argb_u16` and write it to @out_pixel.

diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
index f9045a80aceba941568db014fecf548d59e14a5a..5dad7bcec0a67b8b36fa3e8916c8b8bafd7b3523 100644 (file)
--- a/drivers/gpu/drm/vkms/vkms_formats.c
+++ b/drivers/gpu/drm/vkms/vkms_formats.c
@@ -79,6 +79,38 @@ static void packed_pixels_addr(const struct vkms_frame_info *frame_info,
        *addr = (u8 *)frame_info->map[0].vaddr + offset;
 }
 
+/**
+ * get_block_step_bytes() - Common helper to compute the correct step value between each pixel block
+ * to read in a certain direction.
+ *
+ * @fb: Framebuffer to iter on
+ * @direction: Direction of the reading
+ * @plane_index: Plane to get the step from
+ *
+ * As the returned count is the number of bytes between two consecutive blocks in a direction,
+ * the caller may have to read multiple pixels before using the next one (for example, to read from
+ * left to right in a DRM_FORMAT_R1 plane, each block contains 8 pixels, so the step must be used
+ * only every 8 pixels).
+ */
+static int get_block_step_bytes(struct drm_framebuffer *fb, enum pixel_read_direction direction,
+                               int plane_index)
+{
+       switch (direction) {
+       case READ_LEFT_TO_RIGHT:
+               return fb->format->char_per_block[plane_index];
+       case READ_RIGHT_TO_LEFT:
+               return -fb->format->char_per_block[plane_index];
+       case READ_TOP_TO_BOTTOM:
+               return (int)fb->pitches[plane_index] * drm_format_info_block_width(fb->format,
+                                                                                  plane_index);
+       case READ_BOTTOM_TO_TOP:
+               return -(int)fb->pitches[plane_index] * drm_format_info_block_width(fb->format,
+                                                                                   plane_index);
+       }
+
+       return 0;
+}
+
 /**
  * packed_pixels_addr_1x1() - Get the pointer to the block containing the pixel at the given
  * coordinates