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    Subject[PATCH v12 02/56] media: videobuf2: Rework offset 'cookie' encoding pattern
    Date
    Change how offset 'cookie' field value is computed to make possible
    to use more buffers.
    The maximum number of buffers depends of PAGE_SHIFT value and can
    go up to 0x7fff when PAGE_SHIFT = 12.
    With this encoding pattern we know the maximum number that a queue
    could store so we can check it at queue init time.
    It also make easier and faster to find buffer and plane from using
    the offset field.
    Change __find_plane_by_offset() prototype to return the video buffer
    itself rather than it index.

    Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
    ---
    .../media/common/videobuf2/videobuf2-core.c | 73 +++++++++----------
    1 file changed, 35 insertions(+), 38 deletions(-)

    diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
    index a5e57affeb30..09be8e026044 100644
    --- a/drivers/media/common/videobuf2/videobuf2-core.c
    +++ b/drivers/media/common/videobuf2/videobuf2-core.c
    @@ -31,6 +31,11 @@

    #include <trace/events/vb2.h>

    +#define PLANE_INDEX_SHIFT (PAGE_SHIFT + 3)
    +#define PLANE_INDEX_MASK 0x7
    +#define MAX_BUFFER_INDEX BIT_MASK(30 - PLANE_INDEX_SHIFT)
    +#define BUFFER_INDEX_MASK (MAX_BUFFER_INDEX - 1)
    +
    static int debug;
    module_param(debug, int, 0644);

    @@ -358,21 +363,27 @@ static void __setup_offsets(struct vb2_buffer *vb)
    unsigned int plane;
    unsigned long offset = 0;

    - if (vb->index) {
    - struct vb2_buffer *prev = q->bufs[vb->index - 1];
    - struct vb2_plane *p = &prev->planes[prev->num_planes - 1];
    -
    - offset = PAGE_ALIGN(p->m.offset + p->length);
    - }
    + /*
    + * The offset "cookie" value has the following constraints:
    + * - a buffer can have up to 8 planes.
    + * - v4l2 mem2mem uses bit 30 to distinguish between
    + * OUTPUT (aka "source", bit 30 is 0) and
    + * CAPTURE (aka "destination", bit 30 is 1) buffers.
    + * - must be page aligned
    + * That led to this bit mapping when PAGE_SHIFT = 12:
    + * |30 |29 15|14 12|11 0|
    + * |DST_QUEUE_OFF_BASE|buffer index|plane index| 0 |
    + * where there are 15 bits to store the buffer index.
    + * Depending on PAGE_SHIFT value we can have fewer bits
    + * to store the buffer index.
    + */
    + offset = vb->index << PLANE_INDEX_SHIFT;

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

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

    @@ -2188,10 +2199,9 @@ EXPORT_SYMBOL_GPL(vb2_core_streamoff);
    * __find_plane_by_offset() - find plane associated with the given offset
    */
    static int __find_plane_by_offset(struct vb2_queue *q, unsigned long offset,
    - unsigned int *_buffer, unsigned int *_plane)
    + struct vb2_buffer **vb, unsigned int *plane)
    {
    - struct vb2_buffer *vb;
    - unsigned int buffer, plane;
    + unsigned int buffer;

    /*
    * Sanity checks to ensure the lock is held, MEMORY_MMAP is
    @@ -2209,24 +2219,15 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long offset,
    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 = (offset >> PLANE_INDEX_SHIFT) & BUFFER_INDEX_MASK;
    + *plane = (offset >> PAGE_SHIFT) & PLANE_INDEX_MASK;

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

    - return -EINVAL;
    + *vb = q->bufs[buffer];
    + return 0;
    }

    int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
    @@ -2306,7 +2307,7 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
    {
    unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
    struct vb2_buffer *vb;
    - unsigned int buffer = 0, plane = 0;
    + unsigned int plane = 0;
    int ret;
    unsigned long length;

    @@ -2335,12 +2336,10 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
    * Find the plane corresponding to the offset passed by userspace. This
    * will return an error if not MEMORY_MMAP or file I/O is in progress.
    */
    - ret = __find_plane_by_offset(q, offset, &buffer, &plane);
    + ret = __find_plane_by_offset(q, offset, &vb, &plane);
    if (ret)
    goto unlock;

    - vb = q->bufs[buffer];
    -
    /*
    * MMAP requires page_aligned buffers.
    * The buffer length was page_aligned at __vb2_buf_mem_alloc(),
    @@ -2368,7 +2367,7 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
    if (ret)
    return ret;

    - dprintk(q, 3, "buffer %d, plane %d successfully mapped\n", buffer, plane);
    + dprintk(q, 3, "buffer %u, plane %d successfully mapped\n", vb->index, plane);
    return 0;
    }
    EXPORT_SYMBOL_GPL(vb2_mmap);
    @@ -2382,7 +2381,7 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
    {
    unsigned long offset = pgoff << PAGE_SHIFT;
    struct vb2_buffer *vb;
    - unsigned int buffer, plane;
    + unsigned int plane;
    void *vaddr;
    int ret;

    @@ -2392,12 +2391,10 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
    * Find the plane corresponding to the offset passed by userspace. This
    * will return an error if not MEMORY_MMAP or file I/O is in progress.
    */
    - ret = __find_plane_by_offset(q, offset, &buffer, &plane);
    + ret = __find_plane_by_offset(q, offset, &vb, &plane);
    if (ret)
    goto unlock;

    - vb = q->bufs[buffer];
    -
    vaddr = vb2_plane_vaddr(vb, plane);
    mutex_unlock(&q->mmap_lock);
    return vaddr ? (unsigned long)vaddr : -EINVAL;
    --
    2.39.2
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