media: media/v4l2: remove V4L2_FLAG_MEMORY_NON_CONSISTENT flag

The patch partially reverts some of the UAPI bits of the buffer
cache management hints. Namely, the queue consistency (memory
coherency) user-space hint because, as it turned out, the kernel
implementation of this feature was misusing DMA_ATTR_NON_CONSISTENT.

The patch reverts both kernel and user space parts: removes the
DMA consistency attr functions, rolls back changes to v4l2_requestbuffers,
v4l2_create_buffers structures and corresponding UAPI functions
(plus compat32 layer) and cleans up the documentation.

[hverkuil: fixed a few typos in the commit log]
[hverkuil: fixed vb2_core_reqbufs call in drivers/media/dvb-core/dvb_vb2.c]
[mchehab: fixed a typo in the commit log: revers->reverts]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

4 files changed, 9 insertions, 77 deletions

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index f544d3393e9d..4eab6d81cce1 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -721,39 +721,14 @@ int vb2_verify_memory_type(struct vb2_queue *q,
 }
 EXPORT_SYMBOL(vb2_verify_memory_type);
 
-static void set_queue_consistency(struct vb2_queue *q, bool consistent_mem)
-{
-	q->dma_attrs &= ~DMA_ATTR_NON_CONSISTENT;
-
-	if (!vb2_queue_allows_cache_hints(q))
-		return;
-	if (!consistent_mem)
-		q->dma_attrs |= DMA_ATTR_NON_CONSISTENT;
-}
-
-static bool verify_consistency_attr(struct vb2_queue *q, bool consistent_mem)
-{
-	bool queue_is_consistent = !(q->dma_attrs & DMA_ATTR_NON_CONSISTENT);
-
-	if (consistent_mem != queue_is_consistent) {
-		dprintk(q, 1, "memory consistency model mismatch\n");
-		return false;
-	}
-	return true;
-}
-
 int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
-		     unsigned int flags, unsigned int *count)
+		     unsigned int *count)
 {
 	unsigned int num_buffers, allocated_buffers, num_planes = 0;
 	unsigned plane_sizes[VB2_MAX_PLANES] = { };
-	bool consistent_mem = true;
 	unsigned int i;
 	int ret;
 
-	if (flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
-		consistent_mem = false;
-
 	if (q->streaming) {
 		dprintk(q, 1, "streaming active\n");
 		return -EBUSY;
@@ -765,8 +740,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	}
 
 	if (*count == 0 || q->num_buffers != 0 ||
-	    (q->memory != VB2_MEMORY_UNKNOWN && q->memory != memory) ||
-	    !verify_consistency_attr(q, consistent_mem)) {
+	    (q->memory != VB2_MEMORY_UNKNOWN && q->memory != memory)) {
 		/*
 		 * We already have buffers allocated, so first check if they
 		 * are not in use and can be freed.
@@ -803,7 +777,6 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
 	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
 	q->memory = memory;
-	set_queue_consistency(q, consistent_mem);
 
 	/*
 	 * Ask the driver how many buffers and planes per buffer it requires.
@@ -888,18 +861,14 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 EXPORT_SYMBOL_GPL(vb2_core_reqbufs);
 
 int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
-			 unsigned int flags, unsigned int *count,
+			 unsigned int *count,
 			 unsigned int requested_planes,
 			 const unsigned int requested_sizes[])
 {
 	unsigned int num_planes = 0, num_buffers, allocated_buffers;
 	unsigned plane_sizes[VB2_MAX_PLANES] = { };
-	bool consistent_mem = true;
 	int ret;
 
-	if (flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
-		consistent_mem = false;
-
 	if (q->num_buffers == VB2_MAX_FRAME) {
 		dprintk(q, 1, "maximum number of buffers already allocated\n");
 		return -ENOBUFS;
@@ -912,15 +881,12 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 		}
 		memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
 		q->memory = memory;
-		set_queue_consistency(q, consistent_mem);
 		q->waiting_for_buffers = !q->is_output;
 	} else {
 		if (q->memory != memory) {
 			dprintk(q, 1, "memory model mismatch\n");
 			return -EINVAL;
 		}
-		if (!verify_consistency_attr(q, consistent_mem))
-			return -EINVAL;
 	}
 
 	num_buffers = min(*count, VB2_MAX_FRAME - q->num_buffers);
@@ -2581,7 +2547,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
 	fileio->memory = VB2_MEMORY_MMAP;
 	fileio->type = q->type;
 	q->fileio = fileio;
-	ret = vb2_core_reqbufs(q, fileio->memory, 0, &fileio->count);
+	ret = vb2_core_reqbufs(q, fileio->memory, &fileio->count);
 	if (ret)
 		goto err_kfree;
 
@@ -2638,7 +2604,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
 
 err_reqbufs:
 	fileio->count = 0;
-	vb2_core_reqbufs(q, fileio->memory, 0, &fileio->count);
+	vb2_core_reqbufs(q, fileio->memory, &fileio->count);
 
 err_kfree:
 	q->fileio = NULL;
@@ -2658,7 +2624,7 @@ static int __vb2_cleanup_fileio(struct vb2_queue *q)
 		vb2_core_streamoff(q, q->type);
 		q->fileio = NULL;
 		fileio->count = 0;
-		vb2_core_reqbufs(q, fileio->memory, 0, &fileio->count);
+		vb2_core_reqbufs(q, fileio->memory, &fileio->count);
 		kfree(fileio);
 		dprintk(q, 3, "file io emulator closed\n");
 	}
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index ec3446cc45b8..7b1b86ec942d 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -42,11 +42,6 @@ struct vb2_dc_buf {
 	struct dma_buf_attachment	*db_attach;
 };
 
-static inline bool vb2_dc_buffer_consistent(unsigned long attr)
-{
-	return !(attr & DMA_ATTR_NON_CONSISTENT);
-}
-
 /*********************************************/
 /*        scatterlist table functions        */
 /*********************************************/
@@ -341,13 +336,6 @@ static int
 vb2_dc_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf,
 				   enum dma_data_direction direction)
 {
-	struct vb2_dc_buf *buf = dbuf->priv;
-	struct sg_table *sgt = buf->dma_sgt;
-
-	if (vb2_dc_buffer_consistent(buf->attrs))
-		return 0;
-
-	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
 	return 0;
 }
 
@@ -355,13 +343,6 @@ static int
 vb2_dc_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf,
 				 enum dma_data_direction direction)
 {
-	struct vb2_dc_buf *buf = dbuf->priv;
-	struct sg_table *sgt = buf->dma_sgt;
-
-	if (vb2_dc_buffer_consistent(buf->attrs))
-		return 0;
-
-	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
 	return 0;
 }
 
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
index 0a40e00f0d7e..a86fce5d8ea8 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
@@ -123,8 +123,7 @@ static void *vb2_dma_sg_alloc(struct device *dev, unsigned long dma_attrs,
 	/*
 	 * NOTE: dma-sg allocates memory using the page allocator directly, so
 	 * there is no memory consistency guarantee, hence dma-sg ignores DMA
-	 * attributes passed from the upper layer. That means that
-	 * V4L2_FLAG_MEMORY_NON_CONSISTENT has no effect on dma-sg buffers.
+	 * attributes passed from the upper layer.
 	 */
 	buf->pages = kvmalloc_array(buf->num_pages, sizeof(struct page *),
 				    GFP_KERNEL | __GFP_ZERO);
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 30caad27281e..cfe197df970d 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -722,22 +722,12 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
 #endif
 }
 
-static void clear_consistency_attr(struct vb2_queue *q,
-				   int memory,
-				   unsigned int *flags)
-{
-	if (!q->allow_cache_hints || memory != V4L2_MEMORY_MMAP)
-		*flags &= ~V4L2_FLAG_MEMORY_NON_CONSISTENT;
-}
-
 int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
 {
 	int ret = vb2_verify_memory_type(q, req->memory, req->type);
 
 	fill_buf_caps(q, &req->capabilities);
-	clear_consistency_attr(q, req->memory, &req->flags);
-	return ret ? ret : vb2_core_reqbufs(q, req->memory,
-					    req->flags, &req->count);
+	return ret ? ret : vb2_core_reqbufs(q, req->memory, &req->count);
 }
 EXPORT_SYMBOL_GPL(vb2_reqbufs);
 
@@ -769,7 +759,6 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
 	unsigned i;
 
 	fill_buf_caps(q, &create->capabilities);
-	clear_consistency_attr(q, create->memory, &create->flags);
 	create->index = q->num_buffers;
 	if (create->count == 0)
 		return ret != -EBUSY ? ret : 0;
@@ -813,7 +802,6 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
 		if (requested_sizes[i] == 0)
 			return -EINVAL;
 	return ret ? ret : vb2_core_create_bufs(q, create->memory,
-						create->flags,
 						&create->count,
 						requested_planes,
 						requested_sizes);
@@ -998,12 +986,11 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
 	int res = vb2_verify_memory_type(vdev->queue, p->memory, p->type);
 
 	fill_buf_caps(vdev->queue, &p->capabilities);
-	clear_consistency_attr(vdev->queue, p->memory, &p->flags);
 	if (res)
 		return res;
 	if (vb2_queue_is_busy(vdev, file))
 		return -EBUSY;
-	res = vb2_core_reqbufs(vdev->queue, p->memory, p->flags, &p->count);
+	res = vb2_core_reqbufs(vdev->queue, p->memory, &p->count);
 	/* If count == 0, then the owner has released all buffers and he
 	   is no longer owner of the queue. Otherwise we have a new owner. */
 	if (res == 0)
@@ -1021,7 +1008,6 @@ int vb2_ioctl_create_bufs(struct file *file, void *priv,
 
 	p->index = vdev->queue->num_buffers;
 	fill_buf_caps(vdev->queue, &p->capabilities);
-	clear_consistency_attr(vdev->queue, p->memory, &p->flags);
 	/*
 	 * If count == 0, then just check if memory and type are valid.
 	 * Any -EBUSY result from vb2_verify_memory_type can be mapped to 0.