Re: [PATCH v10 21/54] media: core: Add helper to get queue number of buffers

From: Hans Verkuil
Date: Wed Oct 11 2023 - 04:56:54 EST

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Subject should start with: "media: videobuf2:".

There is another comment at the end...

On 03/10/2023 10:06, Benjamin Gaignard wrote:
> In the future a side effect of introducing DELETE_BUFS ioctl is
> the create of 'holes' (i.e. unused buffers) in bufs arrays.
> To know which entries of the bufs arrays are used a bitmap will
> be added in struct vb2_queue. That will also mean that the number
> of buffers will be computed given the number of bit set in this bitmap.
> To smoothly allow this evolution all drives must stop using
> directly num_buffers field from struct vb2_queue.
> Let do it in 4 steps:
> - Introduce vb2_get_num_buffers() helper
> - Rework how create_bufs first buffer index is computed
> - Rework all drivers to remove direct calls to queue num_buffers
> - Replace num_buffers by a bitmap.
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> ---
> .../media/common/videobuf2/videobuf2-core.c | 109 ++++++++++--------
> .../media/common/videobuf2/videobuf2-v4l2.c | 4 +-
> include/media/videobuf2-core.h | 11 +-
> 3 files changed, 73 insertions(+), 51 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index c0104f824577..62e987ad9b33 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -426,6 +426,8 @@ static void vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, uns
> */
> static void vb2_queue_remove_buffer(struct vb2_buffer *vb)
> {
> + if (vb->vb2_queue->num_buffers)
> + vb->vb2_queue->num_buffers--;
> vb->vb2_queue->bufs[vb->index] = NULL;
> vb->vb2_queue = NULL;
> }
> @@ -509,12 +511,12 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
> */
> static void __vb2_free_mem(struct vb2_queue *q, unsigned int buffers)
> {
> - unsigned int buffer;
> + unsigned int buffer = 0;
> + long i = q->max_num_buffers;
> struct vb2_buffer *vb;
>
> - for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
> - ++buffer) {
> - vb = vb2_get_buffer(q, buffer);
> + for (i = q->max_num_buffers; i >= 0 && buffer < buffers; i--) {
> + vb = vb2_get_buffer(q, i);
> if (!vb)
> continue;
>
> @@ -525,6 +527,7 @@ static void __vb2_free_mem(struct vb2_queue *q, unsigned int buffers)
> __vb2_buf_dmabuf_put(vb);
> else
> __vb2_buf_userptr_put(vb);
> + buffer++;
> }
> }
>
> @@ -536,16 +539,20 @@ static void __vb2_free_mem(struct vb2_queue *q, unsigned int buffers)
> static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
> {
> unsigned int buffer;
> + long i = q->max_num_buffers;
>
> lockdep_assert_held(&q->mmap_lock);
>
> /* Call driver-provided cleanup function for each buffer, if provided */
> - for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
> - ++buffer) {
> - struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
> + for (i = q->max_num_buffers, buffer = 0; i >= 0 && buffer < buffers; i--) {
> + struct vb2_buffer *vb = vb2_get_buffer(q, i);
>
> - if (vb && vb->planes[0].mem_priv)
> + if (!vb)
> + continue;
> + if (vb->planes[0].mem_priv) {
> call_void_vb_qop(vb, buf_cleanup, vb);
> + buffer++;
> + }
> }
>
> /* Release video buffer memory */
> @@ -556,7 +563,7 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
> * Check that all the calls were balanced during the life-time of this
> * queue. If not then dump the counters to the kernel log.
> */
> - if (q->num_buffers) {
> + if (vb2_get_num_buffers(q)) {
> bool unbalanced = q->cnt_start_streaming != q->cnt_stop_streaming ||
> q->cnt_prepare_streaming != q->cnt_unprepare_streaming ||
> q->cnt_wait_prepare != q->cnt_wait_finish;
> @@ -582,7 +589,7 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
> q->cnt_stop_streaming = 0;
> q->cnt_unprepare_streaming = 0;
> }
> - for (buffer = 0; buffer < q->num_buffers; ++buffer) {
> + for (buffer = 0; buffer < q->max_num_buffers; buffer++) {
> struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
> bool unbalanced;
>
> @@ -634,19 +641,18 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
> #endif
>
> /* Free vb2 buffers */
> - for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
> - ++buffer) {
> - struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
> + for (i = q->max_num_buffers, buffer = 0; i >= 0 && buffer < buffers; i--) {
> + struct vb2_buffer *vb = vb2_get_buffer(q, i);
>
> if (!vb)
> continue;
>
> vb2_queue_remove_buffer(vb);
> kfree(vb);
> + buffer++;
> }
>
> - q->num_buffers -= buffers;
> - if (!q->num_buffers) {
> + if (!vb2_get_num_buffers(q)) {
> q->memory = VB2_MEMORY_UNKNOWN;
> INIT_LIST_HEAD(&q->queued_list);
> }
> @@ -677,7 +683,7 @@ EXPORT_SYMBOL(vb2_buffer_in_use);
> static bool __buffers_in_use(struct vb2_queue *q)
> {
> unsigned int buffer;
> - for (buffer = 0; buffer < q->num_buffers; ++buffer) {
> + for (buffer = 0; buffer < q->max_num_buffers; ++buffer) {
> struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>
> if (!vb)
> @@ -803,6 +809,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> unsigned int flags, unsigned int *count)
> {
> unsigned int num_buffers, allocated_buffers, num_planes = 0;
> + 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;
> @@ -818,7 +825,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> return -EBUSY;
> }
>
> - if (*count == 0 || q->num_buffers != 0 ||
> + if (*count == 0 || q_num_bufs != 0 ||
> (q->memory != VB2_MEMORY_UNKNOWN && q->memory != memory) ||
> !verify_coherency_flags(q, non_coherent_mem)) {
> /*
> @@ -836,7 +843,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> * queued without ever calling STREAMON.
> */
> __vb2_queue_cancel(q);
> - __vb2_queue_free(q, q->num_buffers);
> + __vb2_queue_free(q, q_num_bufs);
> mutex_unlock(&q->mmap_lock);
>
> /*
> @@ -936,7 +943,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> if (ret < 0) {
> /*
> * Note: __vb2_queue_free() will subtract 'allocated_buffers'
> - * from q->num_buffers and it will reset q->memory to
> + * from already queued buffers and it will reset q->memory to
> * VB2_MEMORY_UNKNOWN.
> */
> __vb2_queue_free(q, allocated_buffers);
> @@ -970,10 +977,11 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> unsigned int num_planes = 0, num_buffers, allocated_buffers;
> unsigned plane_sizes[VB2_MAX_PLANES] = { };
> bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
> - bool no_previous_buffers = !q->num_buffers;
> + unsigned int q_num_bufs = vb2_get_num_buffers(q);
> + bool no_previous_buffers = !q_num_bufs;
> int ret = 0;
>
> - if (q->num_buffers == q->max_num_buffers) {
> + if (q_num_bufs == q->max_num_buffers) {
> dprintk(q, 1, "maximum number of buffers already allocated\n");
> return -ENOBUFS;
> }
> @@ -1008,7 +1016,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> return -EINVAL;
> }
>
> - num_buffers = min(*count, q->max_num_buffers - q->num_buffers);
> + num_buffers = min(*count, q->max_num_buffers - q_num_bufs);
>
> if (requested_planes && requested_sizes) {
> num_planes = requested_planes;
> @@ -1040,7 +1048,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> num_buffers = allocated_buffers;
>
> /*
> - * q->num_buffers contains the total number of buffers, that the
> + * num_buffers contains the total number of buffers, that the
> * queue driver has set up
> */
> ret = call_qop(q, queue_setup, q, &num_buffers,
> @@ -1061,7 +1069,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> if (ret < 0) {
> /*
> * Note: __vb2_queue_free() will subtract 'allocated_buffers'
> - * from q->num_buffers and it will reset q->memory to
> + * from already queued buffers and it will reset q->memory to
> * VB2_MEMORY_UNKNOWN.
> */
> __vb2_queue_free(q, allocated_buffers);
> @@ -1678,7 +1686,7 @@ static int vb2_start_streaming(struct vb2_queue *q)
> * Forcefully reclaim buffers if the driver did not
> * correctly return them to vb2.
> */
> - for (i = 0; i < q->num_buffers; ++i) {
> + for (i = 0; i < q->max_num_buffers; ++i) {
> vb = vb2_get_buffer(q, i);
>
> if (!vb)
> @@ -2084,9 +2092,8 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
> * to vb2 in stop_streaming().
> */
> if (WARN_ON(atomic_read(&q->owned_by_drv_count))) {
> - for (i = 0; i < q->num_buffers; ++i) {
> + for (i = 0; i < q->max_num_buffers; i++) {
> struct vb2_buffer *vb = vb2_get_buffer(q, i);
> -
> if (!vb)
> continue;
>
> @@ -2128,10 +2135,9 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
> * call to __fill_user_buffer() after buf_finish(). That order can't
> * be changed, so we can't move the buf_finish() to __vb2_dqbuf().
> */
> - for (i = 0; i < q->num_buffers; ++i) {
> + for (i = 0; i < q->max_num_buffers; i++) {
> struct vb2_buffer *vb;
> struct media_request *req;
> -
> vb = vb2_get_buffer(q, i);
> if (!vb)
> continue;
> @@ -2176,6 +2182,7 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
>
> int vb2_core_streamon(struct vb2_queue *q, unsigned int type)
> {
> + unsigned int q_num_bufs = vb2_get_num_buffers(q);
> int ret;
>
> if (type != q->type) {
> @@ -2188,12 +2195,12 @@ int vb2_core_streamon(struct vb2_queue *q, unsigned int type)
> return 0;
> }
>
> - if (!q->num_buffers) {
> + if (!q_num_bufs) {
> dprintk(q, 1, "no buffers have been allocated\n");
> return -EINVAL;
> }
>
> - if (q->num_buffers < q->min_buffers_needed) {
> + if (q_num_bufs < q->min_buffers_needed) {
> dprintk(q, 1, "need at least %u allocated buffers\n",
> q->min_buffers_needed);
> return -EINVAL;
> @@ -2531,9 +2538,10 @@ void vb2_core_queue_release(struct vb2_queue *q)
> __vb2_cleanup_fileio(q);
> __vb2_queue_cancel(q);
> mutex_lock(&q->mmap_lock);
> - __vb2_queue_free(q, q->num_buffers);
> + __vb2_queue_free(q, q->max_num_buffers);
> kfree(q->bufs);
> q->bufs = NULL;
> + q->num_buffers = 0;
> mutex_unlock(&q->mmap_lock);
> }
> EXPORT_SYMBOL_GPL(vb2_core_queue_release);
> @@ -2562,7 +2570,7 @@ __poll_t vb2_core_poll(struct vb2_queue *q, struct file *file,
> /*
> * Start file I/O emulator only if streaming API has not been used yet.
> */
> - if (q->num_buffers == 0 && !vb2_fileio_is_active(q)) {
> + if (vb2_get_num_buffers(q) == 0 && !vb2_fileio_is_active(q)) {
> if (!q->is_output && (q->io_modes & VB2_READ) &&
> (req_events & (EPOLLIN | EPOLLRDNORM))) {
> if (__vb2_init_fileio(q, 1))
> @@ -2600,7 +2608,7 @@ __poll_t vb2_core_poll(struct vb2_queue *q, struct file *file,
> * For output streams you can call write() as long as there are fewer
> * buffers queued than there are buffers available.
> */
> - if (q->is_output && q->fileio && q->queued_count < q->num_buffers)
> + if (q->is_output && q->fileio && q->queued_count < vb2_get_num_buffers(q))
> return EPOLLOUT | EPOLLWRNORM;
>
> if (list_empty(&q->done_list)) {
> @@ -2649,8 +2657,8 @@ struct vb2_fileio_buf {
> * struct vb2_fileio_data - queue context used by file io emulator
> *
> * @cur_index: the index of the buffer currently being read from or
> - * written to. If equal to q->num_buffers then a new buffer
> - * must be dequeued.
> + * written to. If equal to number of already queues buffers
> + * then a new buffer must be dequeued.
> * @initial_index: in the read() case all buffers are queued up immediately
> * in __vb2_init_fileio() and __vb2_perform_fileio() just cycles
> * buffers. However, in the write() case no buffers are initially
> @@ -2660,7 +2668,7 @@ struct vb2_fileio_buf {
> * buffers. This means that initially __vb2_perform_fileio()
> * needs to know what buffer index to use when it is queuing up
> * the buffers for the first time. That initial index is stored
> - * in this field. Once it is equal to q->num_buffers all
> + * in this field. Once it is equal to num_buffers all
> * available buffers have been queued and __vb2_perform_fileio()
> * should start the normal dequeue/queue cycle.
> *
> @@ -2710,7 +2718,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
> /*
> * Check if streaming api has not been already activated.
> */
> - if (q->streaming || q->num_buffers > 0)
> + if (q->streaming || vb2_get_num_buffers(q) > 0)
> return -EBUSY;
>
> /*
> @@ -2760,7 +2768,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
> /*
> * Get kernel address of each buffer.
> */
> - for (i = 0; i < q->num_buffers; i++) {
> + for (i = 0; i < vb2_get_num_buffers(q); i++) {
> vb = vb2_get_buffer(q, i);
> WARN_ON_ONCE(!vb);
>
> @@ -2779,18 +2787,23 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
> /*
> * Queue all buffers.
> */
> - for (i = 0; i < q->num_buffers; i++) {
> - ret = vb2_core_qbuf(q, q->bufs[i], NULL, NULL);
> + for (i = 0; i < vb2_get_num_buffers(q); i++) {
> + struct vb2_buffer *vb2 = vb2_get_buffer(q, i);
> +
> + if (!vb2)
> + continue;
> +
> + ret = vb2_core_qbuf(q, vb2, NULL, NULL);
> if (ret)
> goto err_reqbufs;
> fileio->bufs[i].queued = 1;
> }
> /*
> * All buffers have been queued, so mark that by setting
> - * initial_index to q->num_buffers
> + * initial_index to num_buffers
> */
> - fileio->initial_index = q->num_buffers;
> - fileio->cur_index = q->num_buffers;
> + fileio->initial_index = vb2_get_num_buffers(q);
> + fileio->cur_index = fileio->initial_index;
> }
>
> /*
> @@ -2984,12 +2997,12 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
> * If we are queuing up buffers for the first time, then
> * increase initial_index by one.
> */
> - if (fileio->initial_index < q->num_buffers)
> + if (fileio->initial_index < vb2_get_num_buffers(q))
> fileio->initial_index++;
> /*
> * The next buffer to use is either a buffer that's going to be
> - * queued for the first time (initial_index < q->num_buffers)
> - * or it is equal to q->num_buffers, meaning that the next
> + * queued for the first time (initial_index < num_buffers)
> + * or it is equal to num_buffers, meaning that the next
> * time we need to dequeue a buffer since we've now queued up
> * all the 'first time' buffers.
> */
> @@ -3036,7 +3049,7 @@ static int vb2_thread(void *data)
> int ret = 0;
>
> if (q->is_output) {
> - prequeue = q->num_buffers;
> + prequeue = vb2_get_num_buffers(q);
> copy_timestamp = q->copy_timestamp;
> }
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index cf881c8d8d4d..a4ebef82d94e 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -628,7 +628,7 @@ struct vb2_buffer *vb2_find_buffer(struct vb2_queue *q, u64 timestamp)
> * This loop doesn't scale if there is a really large number of buffers.
> * Maybe something more efficient will be needed in this case.
> */
> - for (i = 0; i < q->num_buffers; i++) {
> + for (i = 0; i < q->max_num_buffers; i++) {
> vb2 = vb2_get_buffer(q, i);
>
> if (!vb2)
> @@ -765,7 +765,7 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
> validate_memory_flags(q, create->memory, &create->flags);
>
> create->max_buffers = q->max_num_buffers;
> - create->index = q->num_buffers;
> + create->index = vb2_get_num_buffers(q);
>
> if (create->count == 0)
> return ret != -EBUSY ? ret : 0;
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 1d6d68e8a711..dffb9647d4d1 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -1141,6 +1141,15 @@ static inline bool vb2_fileio_is_active(struct vb2_queue *q)
> return q->fileio;
> }
>
> +/**
> + * vb2_get_num_buffers() - get the number of buffer in a queue
> + * @q: pointer to &struct vb2_queue with videobuf2 queue.
> + */
> +static inline unsigned int vb2_get_num_buffers(struct vb2_queue *q)
> +{
> + return q->num_buffers;
> +}
> +
> /**
> * vb2_is_busy() - return busy status of the queue.
> * @q: pointer to &struct vb2_queue with videobuf2 queue.
> @@ -1149,7 +1158,7 @@ static inline bool vb2_fileio_is_active(struct vb2_queue *q)
> */
> static inline bool vb2_is_busy(struct vb2_queue *q)
> {
> - return (q->num_buffers > 0);
> + return (vb2_get_num_buffers(q) > 0);

You can drop the outer parenthesis here.

> }
>
> /**

Regards,

Hans

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