media: videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag

This patch lets user-space to request a non-consistent memory
allocation during CREATE_BUFS and REQBUFS ioctl calls.

= CREATE_BUFS

  struct v4l2_create_buffers has seven 4-byte reserved areas,
  so reserved[0] is renamed to ->flags. The struct, thus, now
  has six reserved 4-byte regions.

= CREATE_BUFS32

  struct v4l2_create_buffers32 has seven 4-byte reserved areas,
  so reserved[0] is renamed to ->flags. The struct, thus, now
  has six reserved 4-byte regions.

= REQBUFS

 We use one bit of a ->reserved[1] member of struct v4l2_requestbuffers,
 which is now renamed to ->flags. Unlike v4l2_create_buffers, struct
 v4l2_requestbuffers does not have enough reserved room. Therefore for
 backward compatibility  ->reserved and ->flags were put into anonymous
 union.
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst

@@ -121,7 +121,12 @@ than the number requested.
 	other changes, then set ``count`` to 0, ``memory`` to
 	``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
     * - __u32
-      - ``reserved``\ [7]
+      - ``flags``
+      - Specifies additional buffer management attributes.
+	See :ref:`memory-flags`.
+
+    * - __u32
+      - ``reserved``\ [6]
       - A place holder for future extensions. Drivers and applications
 	must set the array to zero.
 

Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst

@@ -112,10 +112,17 @@ aborting or finishing any DMA in progress, an implicit
 	``V4L2_MEMORY_MMAP`` and ``type`` set to the buffer type. This will
 	free any previously allocated buffers, so this is typically something
 	that will be done at the start of the application.
+    * - union {
+      - (anonymous)
+    * - __u32
+      - ``flags``
+      - Specifies additional buffer management attributes.
+	See :ref:`memory-flags`.
     * - __u32
       - ``reserved``\ [1]
-      - A place holder for future extensions. Drivers and applications
-	must set the array to zero.
+      - Kept for backwards compatibility. Use ``flags`` instead.
+    * - }
+      -
 
 .. tabularcolumns:: |p{6.1cm}|p{2.2cm}|p{8.7cm}|
 

drivers/media/common/videobuf2/videobuf2-core.c

@@ -694,6 +694,9 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	unsigned int i;
 	int ret;
 
+	if (flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
+		consistent_mem = false;
+
 	if (q->streaming) {
 		dprintk(1, "streaming active\n");
 		return -EBUSY;
@@ -837,6 +840,9 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 	bool consistent_mem = true;
 	int ret;
 
+	if (flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
+		consistent_mem = false;
+
 	if (q->num_buffers == VB2_MAX_FRAME) {
 		dprintk(1, "maximum number of buffers already allocated\n");
 		return -ENOBUFS;

drivers/media/common/videobuf2/videobuf2-v4l2.c

@@ -718,12 +718,22 @@ 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);
-	return ret ? ret : vb2_core_reqbufs(q, req->memory, 0, &req->count);
+	clear_consistency_attr(q, req->memory, &req->flags);
+	return ret ? ret : vb2_core_reqbufs(q, req->memory,
+					    req->flags, &req->count);
 }
 EXPORT_SYMBOL_GPL(vb2_reqbufs);
 
@@ -755,6 +765,7 @@ 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;
@@ -797,8 +808,11 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
 	for (i = 0; i < requested_planes; i++)
 		if (requested_sizes[i] == 0)
 			return -EINVAL;
-	return ret ? ret : vb2_core_create_bufs(q, create->memory, 0,
-		&create->count, requested_planes, requested_sizes);
+	return ret ? ret : vb2_core_create_bufs(q, create->memory,
+						create->flags,
+						&create->count,
+						requested_planes,
+						requested_sizes);
 }
 EXPORT_SYMBOL_GPL(vb2_create_bufs);
 
@@ -969,11 +983,12 @@ 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, 0, &p->count);
+	res = vb2_core_reqbufs(vdev->queue, p->memory, p->flags, &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)
@@ -991,6 +1006,7 @@ 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.

drivers/media/v4l2-core/v4l2-compat-ioctl32.c

@@ -246,6 +246,9 @@ struct v4l2_format32 {
  * @memory:	buffer memory type
  * @format:	frame format, for which buffers are requested
  * @capabilities: capabilities of this buffer type.
+ * @flags:	additional buffer management attributes (ignored unless the
+ *		queue has V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS capability and
+ *		configured for MMAP streaming I/O).
  * @reserved:	future extensions
  */
 struct v4l2_create_buffers32 {
@@ -254,7 +257,8 @@ struct v4l2_create_buffers32 {
 	__u32			memory;	/* enum v4l2_memory */
 	struct v4l2_format32	format;
 	__u32			capabilities;
-	__u32			reserved[7];
+	__u32			flags;
+	__u32			reserved[6];
 };
 
 static int __bufsize_v4l2_format(struct v4l2_format32 __user *p32, u32 *size)
@@ -355,7 +359,8 @@ static int get_v4l2_create32(struct v4l2_create_buffers __user *p64,
 {
 	if (!access_ok(p32, sizeof(*p32)) ||
 	    copy_in_user(p64, p32,
-			 offsetof(struct v4l2_create_buffers32, format)))
+			 offsetof(struct v4l2_create_buffers32, format)) ||
+	    assign_in_user(&p64->flags, &p32->flags))
 		return -EFAULT;
 	return __get_v4l2_format32(&p64->format, &p32->format,
 				   aux_buf, aux_space);
@@ -417,6 +422,7 @@ static int put_v4l2_create32(struct v4l2_create_buffers __user *p64,
 	    copy_in_user(p32, p64,
 			 offsetof(struct v4l2_create_buffers32, format)) ||
 	    assign_in_user(&p32->capabilities, &p64->capabilities) ||
+	    assign_in_user(&p32->flags, &p64->flags) ||
 	    copy_in_user(p32->reserved, p64->reserved, sizeof(p64->reserved)))
 		return -EFAULT;
 	return __put_v4l2_format32(&p64->format, &p32->format);

drivers/media/v4l2-core/v4l2-ioctl.c

@@ -2038,9 +2038,6 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
 
 	if (ret)
 		return ret;
-
-	CLEAR_AFTER_FIELD(p, capabilities);
-
 	return ops->vidioc_reqbufs(file, fh, p);
 }
 
@@ -2080,7 +2077,7 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
 	if (ret)
 		return ret;
 
-	CLEAR_AFTER_FIELD(create, capabilities);
+	CLEAR_AFTER_FIELD(create, flags);
 
 	v4l_sanitize_format(&create->format);
 

include/uapi/linux/videodev2.h

@@ -946,7 +946,10 @@ struct v4l2_requestbuffers {
 	__u32			type;		/* enum v4l2_buf_type */
 	__u32			memory;		/* enum v4l2_memory */
 	__u32			capabilities;
-	__u32			reserved[1];
+	union {
+		__u32		flags;
+		__u32		reserved[1];
+	};
 };
 
 /* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */
@@ -2450,6 +2453,9 @@ struct v4l2_dbg_chip_info {
  * @memory:	enum v4l2_memory; buffer memory type
  * @format:	frame format, for which buffers are requested
  * @capabilities: capabilities of this buffer type.
+ * @flags:	additional buffer management attributes (ignored unless the
+ *		queue has V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS capability
+ *		and configured for MMAP streaming I/O).
  * @reserved:	future extensions
  */
 struct v4l2_create_buffers {
@@ -2458,7 +2464,8 @@ struct v4l2_create_buffers {
 	__u32			memory;
 	struct v4l2_format	format;
 	__u32			capabilities;
-	__u32			reserved[7];
+	__u32			flags;
+	__u32			reserved[6];
 };
 
 /*