Re: [PATCH v17 3/8] media: core: Rework how create_buf index returned value is computed

From: Hans Verkuil
Date: Wed Jan 24 2024 - 06:20:57 EST

On 19/01/2024 10:49, Benjamin Gaignard wrote:
> When DELETE_BUFS will be introduced holes could created in bufs array.
> To be able to reuse these unused indices reworking how create->index
> is set is mandatory.
> Let __vb2_queue_alloc() decide which first index is correct and
> forward this to the caller.
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> ---
> version 17:
> - rework documentation
> .../media/common/videobuf2/videobuf2-core.c | 18 +++++++++++++-----
> .../media/common/videobuf2/videobuf2-v4l2.c | 14 +++++++++-----
> include/media/videobuf2-core.h | 5 ++++-
> 3 files changed, 26 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index d74e93d00f58..fd5ac2845018 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -442,12 +442,15 @@ static void vb2_queue_remove_buffer(struct vb2_buffer *vb)
> * __vb2_queue_alloc() - allocate vb2 buffer structures and (for MMAP type)
> * video buffer memory for all buffers/planes on the queue and initializes the
> * queue
> + * @first_index: index of the first created buffer, all allocated buffers have

allocated -> newly allocated

> + * indices in the range [first..first+count]

That should be: [first_index..first_index+count-1]

> *
> * Returns the number of buffers successfully allocated.
> */
> static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
> unsigned int num_buffers, unsigned int num_planes,
> - const unsigned plane_sizes[VB2_MAX_PLANES])
> + const unsigned int plane_sizes[VB2_MAX_PLANES],
> + unsigned int *first_index)
> {
> unsigned int q_num_buffers = vb2_get_num_buffers(q);
> unsigned int buffer, plane;
> @@ -461,6 +464,8 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
> num_buffers = min_t(unsigned int, num_buffers,
> q->max_num_buffers - q_num_buffers);
>
> + *first_index = q_num_buffers;
> +
> for (buffer = 0; buffer < num_buffers; ++buffer) {
> /* Allocate vb2 buffer structures */
> vb = kzalloc(q->buf_struct_size, GFP_KERNEL);
> @@ -820,7 +825,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> unsigned int q_num_bufs = vb2_get_num_buffers(q);
> unsigned plane_sizes[VB2_MAX_PLANES] = { };
> bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
> - unsigned int i;
> + unsigned int i, first_index;
> int ret = 0;
>
> if (q->streaming) {
> @@ -906,8 +911,10 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>
> /* Finally, allocate buffers and video memory */
> allocated_buffers =
> - __vb2_queue_alloc(q, memory, num_buffers, num_planes, plane_sizes);
> + __vb2_queue_alloc(q, memory, num_buffers, num_planes, plane_sizes, &first_index);
> if (allocated_buffers == 0) {
> + /* There shouldn't be any buffers allocated, so first_index == 0 */
> + WARN_ON(first_index);
> dprintk(q, 1, "memory allocation failed\n");
> ret = -ENOMEM;
> goto error;
> @@ -980,7 +987,8 @@ EXPORT_SYMBOL_GPL(vb2_core_reqbufs);
> int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> unsigned int flags, unsigned int *count,
> unsigned int requested_planes,
> - const unsigned int requested_sizes[])
> + const unsigned int requested_sizes[],
> + unsigned int *first_index)
> {
> unsigned int num_planes = 0, num_buffers, allocated_buffers;
> unsigned plane_sizes[VB2_MAX_PLANES] = { };
> @@ -1042,7 +1050,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>
> /* Finally, allocate buffers and video memory */
> allocated_buffers = __vb2_queue_alloc(q, memory, num_buffers,
> - num_planes, plane_sizes);
> + num_planes, plane_sizes, first_index);
> if (allocated_buffers == 0) {
> dprintk(q, 1, "memory allocation failed\n");
> ret = -ENOMEM;
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index c575198e8354..03e8080a68a8 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -795,11 +795,15 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
> for (i = 0; i < requested_planes; i++)
> if (requested_sizes[i] == 0)
> return -EINVAL;
> - return ret ? ret : vb2_core_create_bufs(q, create->memory,
> - create->flags,
> - &create->count,
> - requested_planes,
> - requested_sizes);
> + if (ret)
> + return ret;
> +
> + return vb2_core_create_bufs(q, create->memory,
> + create->flags,
> + &create->count,
> + requested_planes,
> + requested_sizes,
> + &create->index);
> }
> EXPORT_SYMBOL_GPL(vb2_create_bufs);
>
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index fe3423ff3807..e29ff77814d3 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -821,6 +821,8 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> * @count: requested buffer count.
> * @requested_planes: number of planes requested.
> * @requested_sizes: array with the size of the planes.
> + * @first_index: index of the first created buffer, all allocated buffers have
> + * indices in the range [first..first+count]

Same changes needed as in the source comments.

> *
> * Videobuf2 core helper to implement VIDIOC_CREATE_BUFS() operation. It is
> * called internally by VB2 by an API-specific handler, like
> @@ -837,7 +839,8 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> unsigned int flags, unsigned int *count,
> unsigned int requested_planes,
> - const unsigned int requested_sizes[]);
> + const unsigned int requested_sizes[],
> + unsigned int *first_index);
>
> /**
> * vb2_core_prepare_buf() - Pass ownership of a buffer from userspace

Regards,

Hans