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

[Benjamin Gaignard <benjamin.gaignard@collabora.com>]

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@collabora.com>
---
 .../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);
+
 	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