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Subject[RFC][PATCH 05/15] videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT in REQBUFS
Date
This patch lets user-space to request a non-consistent memory
allocation during REQBUFS ioctl call. We use one bit of a
->reserved[1] member of struct v4l2_requestbuffers, which is
now renamed to ->flags.

There is just 1 four-byte reserved area in v4l2_requestbuffers
struct, therefore for backward compatibility ->reserved and
->flags were put into anonymous union.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
Documentation/media/uapi/v4l/vidioc-reqbufs.rst | 14 ++++++++++++--
drivers/media/common/videobuf2/videobuf2-v4l2.c | 14 ++++++++++++--
drivers/media/v4l2-core/v4l2-ioctl.c | 3 ---
include/uapi/linux/videodev2.h | 5 ++++-
4 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
index d0c643db477a..9b69a61d9fd4 100644
--- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
+++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
@@ -112,10 +112,20 @@ 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.
- * - __u32
+ * - union
+ - (anonymous)
+ * -
+ - __u32
+ - ``flags``\ [1]
+ - Specifies additional buffer management attributes. E.g. when
+ ``V4L2_FLAG_MEMORY_NON_CONSISTENT`` set vb2 backends may be allocated
+ in non-consistent memory.
+ * -
+ - __u32
- ``reserved``\ [1]
- A place holder for future extensions. Drivers and applications
- must set the array to zero.
+ must set the array to zero, unless application wants to specify
+ buffer management ``flags``.

.. tabularcolumns:: |p{6.1cm}|p{2.2cm}|p{8.7cm}|

diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index f1e88c9398c7..0eabb589684f 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -693,9 +693,15 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
{
int ret = vb2_verify_memory_type(q, req->memory, req->type);
+ bool consistent = true;
+
+ if (req->flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
+ consistent = false;

fill_buf_caps(q, &req->capabilities);
- return ret ? ret : vb2_core_reqbufs(q, req->memory, true, &req->count);
+ if (ret)
+ return ret;
+ return vb2_core_reqbufs(q, req->memory, consistent, &req->count);
}
EXPORT_SYMBOL_GPL(vb2_reqbufs);

@@ -939,13 +945,17 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
{
struct video_device *vdev = video_devdata(file);
int res = vb2_verify_memory_type(vdev->queue, p->memory, p->type);
+ bool consistent = true;

fill_buf_caps(vdev->queue, &p->capabilities);
if (res)
return res;
if (vb2_queue_is_busy(vdev, file))
return -EBUSY;
- res = vb2_core_reqbufs(vdev->queue, p->memory, true, &p->count);
+ if (p->flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
+ consistent = false;
+
+ res = vb2_core_reqbufs(vdev->queue, p->memory, consistent, &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)
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index 003b7422aeef..225d06819bce 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -1973,9 +1973,6 @@ 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);
}

diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index d352997f2b62..73a4854f71bd 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -919,7 +919,10 @@ 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 */
--
2.24.1.735.g03f4e72817-goog
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