RE: [EXT] [RFC 3/4] media: videobuf2: Use bitmap to manage vb2 index

[Ming Qian]

>Using a bitmap to get vb2 index will allow to avoid holes in the indexes when
>introducing DELETE_BUF ioctl.
>
>Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
>---
> .../media/common/videobuf2/videobuf2-core.c   | 22 ++++++++++++++++++-
> include/media/videobuf2-core.h                |  6 +++++
> 2 files changed, 27 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
>b/drivers/media/common/videobuf2/videobuf2-core.c
>index 96597d339a07..3554811ec06a 100644
>--- a/drivers/media/common/videobuf2/videobuf2-core.c
>+++ b/drivers/media/common/videobuf2/videobuf2-core.c
>@@ -397,6 +397,22 @@ static void init_buffer_cache_hints(struct vb2_queue
>*q, struct vb2_buffer *vb)
>                vb->skip_cache_sync_on_finish = 1;  }
>
>+/*
>+ * __vb2_get_index() - find a free index in the queue for vb2 buffer.
>+ *
>+ * Returns an index for vb2 buffer.
>+ */
>+static int __vb2_get_index(struct vb2_queue *q) {
>+       unsigned long index;
>+
>+       index = bitmap_find_next_zero_area(q->bmap, q->idx_max, 0, 1, 0);
>+       if (index > q->idx_max)
>+               dprintk(q, 1, "no index available for buffer\n");
>+
>+       return index;
>+}
>+
> /*
>  * __vb2_queue_alloc() - allocate vb2 buffer structures and (for MMAP type)
>  * video buffer memory for all buffers/planes on the queue and initializes the
>@@ -423,7 +439,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q,
>enum vb2_memory memory,
>                vb->state = VB2_BUF_STATE_DEQUEUED;
>                vb->vb2_queue = q;
>                vb->num_planes = num_planes;
>-               vb->index = q->num_buffers + buffer;
>+               vb->index = __vb2_get_index(q);
>                vb->type = q->type;
>                vb->memory = memory;
>                init_buffer_cache_hints(q, vb); @@ -2438,6 +2454,9 @@ int
>vb2_core_queue_init(struct vb2_queue *q)
>        mutex_init(&q->mmap_lock);
>        init_waitqueue_head(&q->done_wq);
>
>+       q->idx_max = ALIGN(256, BITS_PER_LONG);
>+       q->bmap = bitmap_zalloc(q->idx_max, GFP_KERNEL);
>+

Hi Benjamin,

    Does it mean the maximum vb2 buffer count is enlarged to 256?
    What will happen if user create the 257th buffer?

Ming

>        q->memory = VB2_MEMORY_UNKNOWN;
>
>        if (q->buf_struct_size == 0)
>@@ -2465,6 +2484,7 @@ void vb2_core_queue_release(struct vb2_queue *q)
>        mutex_lock(&q->mmap_lock);
>        __vb2_queue_free(q, q->num_buffers);
>        mutex_unlock(&q->mmap_lock);
>+       bitmap_free(q->bmap);
> }
> EXPORT_SYMBOL_GPL(vb2_core_queue_release);
>
>diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-
>core.h index 47f1f35eb9cb..4fddc6ae9f20 100644
>--- a/include/media/videobuf2-core.h
>+++ b/include/media/videobuf2-core.h
>@@ -561,6 +561,8 @@ struct vb2_buf_ops {
>  * @dma_dir:   DMA mapping direction.
>  * @allocated_bufs: list of buffer allocated for the queue.
>  * @num_buffers: number of allocated/used buffers
>+ * @bmap: Bitmap of buffers index
>+ * @idx_max: number of bits in bmap
>  * @queued_list: list of buffers currently queued from userspace
>  * @queued_count: number of buffers queued and ready for streaming.
>  * @owned_by_drv_count: number of buffers owned by the driver @@ -
>624,6 +626,8 @@ struct vb2_queue {
>        enum dma_data_direction         dma_dir;
>        struct list_head                allocated_bufs;
>        unsigned int                    num_buffers;
>+       unsigned long                   *bmap;
>+       int                             idx_max;
>
>        struct list_head                queued_list;
>        unsigned int                    queued_count;
>@@ -1259,6 +1263,7 @@ static inline struct vb2_buffer
>*vb2_get_buffer(struct vb2_queue *q,  static inline void vb2_set_buffer(struct
>vb2_queue *q, struct vb2_buffer *vb)  {
>        list_add_tail(&vb->allocated_entry, &q->allocated_bufs);
>+       __set_bit(vb->index, q->bmap);
> }
>
> /**
>@@ -1268,6 +1273,7 @@ static inline void vb2_set_buffer(struct vb2_queue
>*q, struct vb2_buffer *vb)
>  */
> static inline void vb2_del_buffer(struct vb2_queue *q, struct vb2_buffer *vb)
>{
>+       __clear_bit(vb->index, q->bmap);
>        list_del(&vb->allocated_entry);
> }
>
>--
>2.34.1