Le 15/01/2024 à 13:21, Hans Verkuil a écrit :
On 15/12/2023 10:08, Benjamin Gaignard wrote:
Add a bitmap field to know which of bufs array entries are
used or not.
Remove no more used num_buffers field from queue structure.
Use bitmap_find_next_zero_area() to find the first possible
range when creating new buffers to fill the gaps.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
---
.../media/common/videobuf2/videobuf2-core.c | 37 ++++++++++++++++---
include/media/videobuf2-core.h | 17 +++++----
2 files changed, 41 insertions(+), 13 deletions(-)
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index cd2b9e51b9b0..9509535a980c 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -421,11 +421,12 @@ static void init_buffer_cache_hints(struct vb2_queue *q, struct vb2_buffer *vb)
*/
static void vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, unsigned int index)
{
- WARN_ON(index >= q->max_num_buffers || q->bufs[index] || vb->vb2_queue);
+ WARN_ON(index >= q->max_num_buffers || test_bit(index, q->bufs_bitmap) || vb->vb2_queue);
q->bufs[index] = vb;
vb->index = index;
vb->vb2_queue = q;
+ set_bit(index, q->bufs_bitmap);
}
/**
@@ -434,6 +435,7 @@ 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)
{
+ clear_bit(vb->index, vb->vb2_queue->bufs_bitmap);
vb->vb2_queue->bufs[vb->index] = NULL;
vb->vb2_queue = NULL;
}
@@ -462,7 +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 - vb2_get_num_buffers(q));
- index = vb2_get_num_buffers(q);
+ index = bitmap_find_next_zero_area(q->bufs_bitmap, q->max_num_buffers,
+ 0, num_buffers, 0);
Shouldn't this check if this call fails to find an area of 'num_buffers' 0-bits?
Or, alternatively, keep reducing num_buffers until it finds a free range. I'm
not sure what is best.
I will add a check on the return value. If it can't allocate the requested number of buffers
it will fail. Userspace can decide if it wants to try allocated less buffers or not.
*first_index = index;
@@ -664,7 +667,6 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
kfree(vb);
}
- q->num_buffers -= buffers;
if (!vb2_get_num_buffers(q)) {
q->memory = VB2_MEMORY_UNKNOWN;
INIT_LIST_HEAD(&q->queued_list);
@@ -882,6 +884,14 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
if (!q->bufs)
ret = -ENOMEM;
+
+ if (!q->bufs_bitmap)
+ q->bufs_bitmap = bitmap_zalloc(q->max_num_buffers, GFP_KERNEL);
+ if (!q->bufs_bitmap) {
+ ret = -ENOMEM;
+ kfree(q->bufs);
+ q->bufs = NULL;
+ }
q->memory = memory;
mutex_unlock(&q->mmap_lock);
if (ret)
@@ -951,7 +961,6 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
}
mutex_lock(&q->mmap_lock);
- q->num_buffers = allocated_buffers;
if (ret < 0) {
/*
@@ -978,6 +987,10 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
mutex_lock(&q->mmap_lock);
q->memory = VB2_MEMORY_UNKNOWN;
mutex_unlock(&q->mmap_lock);
+ kfree(q->bufs);
+ q->bufs = NULL;
+ bitmap_free(q->bufs_bitmap);
+ q->bufs_bitmap = NULL;
return ret;
}
EXPORT_SYMBOL_GPL(vb2_core_reqbufs);
@@ -1014,9 +1027,19 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
q->memory = memory;
if (!q->bufs)
q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
- if (!q->bufs)
+ if (!q->bufs) {
ret = -ENOMEM;
+ goto unlock;
+ }
+ if (!q->bufs_bitmap)
+ q->bufs_bitmap = bitmap_zalloc(q->max_num_buffers, GFP_KERNEL);
+ if (!q->bufs_bitmap) {
+ ret = -ENOMEM;
+ kfree(q->bufs);
+ q->bufs = NULL;
+ }
The same code is used in reqbufs and create_bufs, so perhaps creating a helper
function is better.
I will add vb2_core_allocated_queue_buffers_storage() and vb2_core_free_queue_buffers_storage().
mutex_unlock(&q->mmap_lock);
+unlock:
if (ret)
return ret;
q->waiting_for_buffers = !q->is_output;
@@ -1078,7 +1101,6 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
}
mutex_lock(&q->mmap_lock);
- q->num_buffers += allocated_buffers;
if (ret < 0) {
/*
@@ -2567,6 +2589,9 @@ void vb2_core_queue_release(struct vb2_queue *q)
__vb2_queue_free(q, vb2_get_num_buffers(q));
kfree(q->bufs);
q->bufs = NULL;
+ bitmap_free(q->bufs_bitmap);
+ q->bufs_bitmap = NULL;
+
And perhaps also a helper function to free the memory.
mutex_unlock(&q->mmap_lock);
}
EXPORT_SYMBOL_GPL(vb2_core_queue_release);
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 607f2ba7a905..e4c1fc7ae82f 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -346,8 +346,8 @@ struct vb2_buffer {
* describes the requested number of planes and sizes\[\]
* contains the requested plane sizes. In this case
* \*num_buffers are being allocated additionally to
- * q->num_buffers. If either \*num_planes or the requested
- * sizes are invalid callback must return %-EINVAL.
+ * the buffers already in the queue. If either \*num_planes
already in the queue -> already allocated
+ * or the requested sizes are invalid callback must return %-EINVAL.
* @wait_prepare: release any locks taken while calling vb2 functions;
* it is called before an ioctl needs to wait for a new
* buffer to arrive; required to avoid a deadlock in
@@ -572,7 +572,7 @@ struct vb2_buf_ops {
* @memory: current memory type used
* @dma_dir: DMA mapping direction.
* @bufs: videobuf2 buffer structures
- * @num_buffers: number of allocated/used buffers
+ * @bufs_bitmap: bitmap tracking whether each bufs[] entry is used
* @max_num_buffers: upper limit of number of allocated/used buffers.
* If set to 0 v4l2 core will change it VB2_MAX_FRAME
* for backward compatibility.
@@ -639,7 +639,7 @@ struct vb2_queue {
unsigned int memory;
enum dma_data_direction dma_dir;
struct vb2_buffer **bufs;
- unsigned int num_buffers;
+ unsigned long *bufs_bitmap;
unsigned int max_num_buffers;
struct list_head queued_list;
@@ -1168,7 +1168,10 @@ static inline bool vb2_fileio_is_active(struct vb2_queue *q)
*/
static inline unsigned int vb2_get_num_buffers(struct vb2_queue *q)
{
- return q->num_buffers;
+ if (!q->bufs_bitmap)
+ return 0;
+
+ return bitmap_weight(q->bufs_bitmap, q->max_num_buffers);
I'd invert the test:
if (q->bufs_bitmap)
return bitmap_weight(q->bufs_bitmap, q->max_num_buffers);
return 0;
It's a little bit easier to read.
}
/**
@@ -1271,13 +1274,13 @@ 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 (!q->bufs)
+ if (!q->bufs_bitmap)
Can you ever have q->bufs set, but not q->bufs_bitmap?
I think the original check is just fine.
It is probably a good idea to perhaps clarify this in the @bufs documentation:
if it is non-NULL, then bufs_bitmap is also non-NULL.
And ensure that where you allocate and assign these fields that bufs_bitmap
is always non-NULL when assigning q->bufs. Then it is enough to just test
q->bufs to be certain both bufs and bufs_bitmap are non-NULL.
I will add that in the documentation.
return NULL;
if (index >= q->max_num_buffers)
return NULL;
- if (index < q->num_buffers)
+ if (test_bit(index, q->bufs_bitmap))
return q->bufs[index];
return NULL;
}
Adding support for deleting buffers also causes a odd change in behavior
of CREATE_BUFS w.r.t. the index field of struct v4l2_create_buffers:
when adding new buffers, the index field is indeed the starting buffer index,
as per the documentation. But if count == 0, then the index field returns
the total number of allocated buffers, which is really something different.
I think the documentation of VIDIOC_CREATE_BUFS should be updated to clearly
state that if count == 0, then 'index' is set to the total number of
allocated buffers.
I really hate VIDIOC_CREATE_BUFS, and I do plan an RFC with a proposal for
an alternative API.
Regards,
Hans
