Re: [PATCH v2 2/8] media: videobuf2: Make bufs array dynamic allocated

[Laurent Pinchart]

Hi Benjamin,

Thank you for the patch.

On Tue, Mar 21, 2023 at 11:28:49AM +0100, Benjamin Gaignard wrote:
> Instead of a static array change bufs to a dynamically allocated array.
> This will allow to store more video buffer if needed.
> Protect the array with a spinlock.

I think I asked in the review of v1 why we couldn't use the kernel
IDA/IDR APIs to allocate buffer IDs and register buffers, but I don't
think I've received a reply. Wouldn't it be better than rolling out our
own mechanism ?

> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> ---
>  .../media/common/videobuf2/videobuf2-core.c   |  8 +++
>  include/media/videobuf2-core.h                | 49 ++++++++++++++++---
>  2 files changed, 49 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 79e90e338846..ae9d72f4d181 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -2452,6 +2452,13 @@ int vb2_core_queue_init(struct vb2_queue *q)
>  	mutex_init(&q->mmap_lock);
>  	init_waitqueue_head(&q->done_wq);
>  
> +	q->max_num_bufs = 32;
> +	q->bufs = kmalloc_array(q->max_num_bufs, sizeof(*q->bufs), GFP_KERNEL | __GFP_ZERO);
> +	if (!q->bufs)
> +		return -ENOMEM;
> +
> +	spin_lock_init(&q->bufs_lock);
> +
>  	q->memory = VB2_MEMORY_UNKNOWN;
>  
>  	if (q->buf_struct_size == 0)
> @@ -2479,6 +2486,7 @@ 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);
> +	kfree(q->bufs);
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_queue_release);
>  
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 5b1e3d801546..397dbf6e61e1 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -558,6 +558,8 @@ struct vb2_buf_ops {
>   * @dma_dir:	DMA mapping direction.
>   * @bufs:	videobuf2 buffer structures
>   * @num_buffers: number of allocated/used buffers
> + * @bufs_lock: lock to protect bufs access
> + * @max_num_bufs: max number of buffers storable in bufs
>   * @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
> @@ -619,8 +621,10 @@ struct vb2_queue {
>  	struct mutex			mmap_lock;
>  	unsigned int			memory;
>  	enum dma_data_direction		dma_dir;
> -	struct vb2_buffer		*bufs[VB2_MAX_FRAME];
> +	struct vb2_buffer		**bufs;
>  	unsigned int			num_buffers;
> +	spinlock_t			bufs_lock;
> +	size_t				max_num_bufs;
>  
>  	struct list_head		queued_list;
>  	unsigned int			queued_count;
> @@ -1239,9 +1243,16 @@ static inline void vb2_clear_last_buffer_dequeued(struct vb2_queue *q)
>  static inline struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q,
>  						unsigned int index)
>  {
> -	if (index < q->num_buffers)
> -		return q->bufs[index];
> -	return NULL;
> +	struct vb2_buffer *vb = NULL;
> +
> +	spin_lock(&q->bufs_lock);
> +
> +	if (index < q->max_num_bufs)
> +		vb = q->bufs[index];
> +
> +	spin_unlock(&q->bufs_lock);
> +
> +	return vb;
>  }
>  
>  /**
> @@ -1251,12 +1262,30 @@ static inline struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q,
>   */
>  static inline bool vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb)
>  {
> -	if (vb->index < VB2_MAX_FRAME) {
> +	bool ret = false;
> +
> +	spin_lock(&q->bufs_lock);
> +
> +	if (vb->index >= q->max_num_bufs) {
> +		struct vb2_buffer **tmp;
> +
> +		tmp = krealloc_array(q->bufs, q->max_num_bufs * 2, sizeof(*q->bufs), GFP_KERNEL);
> +		if (!tmp)
> +			goto realloc_failed;
> +
> +		q->max_num_bufs *= 2;
> +		q->bufs = tmp;
> +	}
> +
> +	if (vb->index < q->max_num_bufs) {
>  		q->bufs[vb->index] = vb;
> -		return true;
> +		ret = true;
>  	}
>  
> -	return false;
> +realloc_failed:
> +	spin_unlock(&q->bufs_lock);
> +
> +	return ret;
>  }
>  
>  /**
> @@ -1266,8 +1295,12 @@ static inline bool vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *
>   */
>  static inline void vb2_queue_remove_buffer(struct vb2_queue *q, struct vb2_buffer *vb)
>  {
> -	if (vb->index < VB2_MAX_FRAME)
> +	spin_lock(&q->bufs_lock);
> +
> +	if (vb->index < q->max_num_bufs)
>  		q->bufs[vb->index] = NULL;
> +
> +	spin_unlock(&q->bufs_lock);
>  }
>  
>  /*

-- 
Regards,

Laurent Pinchart