[PATCH v7 01/49] media: videobuf2: Rework offset 'cookie' encoding pattern

Benjamin Gaignard
2023-09-14T13:33:39Z

Change how offset 'cookie' field value is computed to make possible
to use more buffers (up to 0x7fff)
With this encoding pattern we know the maximum number that a queue
could store so we can check ing at queue init time.
It also make easier and faster to find buffer and plane from using
the offset field.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
---
.../media/common/videobuf2/videobuf2-core.c | 48 +++++++++----------
1 file changed, 24 insertions(+), 24 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index cf6727d9c81f..cf3b9f5b69b7 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -31,6 +31,10 @@

#include <trace/events/vb2.h>

+#define PLANE_INDEX_SHIFT (PAGE_SHIFT + 3)
+#define PLANE_INDEX_MASK 0x7
+#define BUFFER_INDEX_MASK 0x7fff
+
static int debug;
module_param(debug, int, 0644);

@@ -358,21 +362,23 @@ static void __setup_offsets(struct vb2_buffer *vb)
unsigned int plane;
unsigned long off = 0;

- if (vb->index) {
- struct vb2_buffer *prev = q->bufs[vb->index - 1];
- struct vb2_plane *p = &prev->planes[prev->num_planes - 1];
-
- off = PAGE_ALIGN(p->m.offset + p->length);
- }
+ /*
+ * Offsets cookies value have the following constraints:
+ * - a buffer could have up to 8 planes.
+ * - v4l2 mem2mem use bit 30 to distinguish between source and destination buffers.
+ * - must be page aligned
+ * That led to this bit mapping:
+ * |30 |29 15|14 12|11 0|
+ * |DST_QUEUE_OFF_BASE|buffer index|plane index| 0 |
+ * where there is 15 bits to store buffer index.
+ */
+ off = vb->index << (PLANE_INDEX_SHIFT);

for (plane = 0; plane < vb->num_planes; ++plane) {
- vb->planes[plane].m.offset = off;
+ vb->planes[plane].m.offset = off + (plane << PAGE_SHIFT);

dprintk(q, 3, "buffer %d, plane %d offset 0x%08lx\n",
vb->index, plane, off);
-
- off += vb->planes[plane].length;
- off = PAGE_ALIGN(off);
}
}

@@ -2209,21 +2215,15 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off,
return -EBUSY;
}

- /*
- * Go over all buffers and their planes, comparing the given offset
- * with an offset assigned to each plane. If a match is found,
- * return its buffer and plane numbers.
- */
- for (buffer = 0; buffer < q->num_buffers; ++buffer) {
- vb = q->bufs[buffer];
+ /* Get buffer and plane from the offset */
+ buffer = (off >> PLANE_INDEX_SHIFT) & BUFFER_INDEX_MASK;
+ plane = (off >> PAGE_SHIFT) & PLANE_INDEX_MASK;

- for (plane = 0; plane < vb->num_planes; ++plane) {
- if (vb->planes[plane].m.offset == off) {
- *_buffer = buffer;
- *_plane = plane;
- return 0;
- }
- }
+ vb = q->bufs[buffer];
+ if (vb->planes[plane].m.offset == off) {
+ *_buffer = buffer;
+ *_plane = plane;
+ return 0;
}

return -EINVAL;
--
2.39.2