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.
Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
---
drivers/gpu/drm/vkms/vkms_composer.c | 46 ++++++++++++++++++++++++++++++++++++
drivers/gpu/drm/vkms/vkms_drv.h | 11 +++++++++
drivers/gpu/drm/vkms/vkms_formats.c | 30 +++++++++++++++++++++++
3 files changed, 87 insertions(+)
diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
index 45b111c74884..fb4967a00398 100644
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -159,6 +159,52 @@ 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 17081effe99a..5d0e87fe50c0 100644
--- 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 internaly 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 9a1400ad4db6..e4cc8948e4d5 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.c
+++ b/drivers/gpu/drm/vkms/vkms_formats.c
@@ -75,6 +75,36 @@ 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];
+ case READ_BOTTOM_TO_TOP:
+ return -(int)fb->pitches[plane_index];
+ }
+
+ return 0;
+}
+
/**
* packed_pixels_addr_1x1() - Get the pointer to the block containing the pixel at the given
* coordinates
--
2.43.2
