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Message-ID: <7f3310f9-8a12-1299-726d-2ca04207b32c@xs4all.nl>
Date: Wed, 19 Feb 2020 09:25:46 +0100
From: Hans Verkuil <hverkuil@...all.nl>
To: Sergey Senozhatsky <senozhatsky@...omium.org>,
Hans Verkuil <hans.verkuil@...co.com>,
Tomasz Figa <tfiga@...omium.org>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Kyungmin Park <kyungmin.park@...sung.com>,
Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Sakari Ailus <sakari.ailus@....fi>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Pawel Osciak <posciak@...omium.org>,
linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCHv2 05/12] videobuf2: handle
V4L2_FLAG_MEMORY_NON_CONSISTENT flag
On 2/4/20 3:56 AM, Sergey Senozhatsky wrote:
> 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.
>
> = 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.
>
> Change-Id: I0eaab3428de499ce1bce6fc6b26c5ca5ff405882
> Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> ---
> .../media/uapi/v4l/vidioc-create-bufs.rst | 9 +++++++-
> .../media/uapi/v4l/vidioc-reqbufs.rst | 15 ++++++++++---
> .../media/common/videobuf2/videobuf2-v4l2.c | 21 ++++++++++++++++---
> drivers/media/v4l2-core/v4l2-ioctl.c | 5 +----
> include/uapi/linux/videodev2.h | 8 +++++--
> 5 files changed, 45 insertions(+), 13 deletions(-)
>
> diff --git a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
> index bd08e4f77ae4..68185e94b686 100644
> --- a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
> @@ -121,7 +121,14 @@ 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. Valid only when
> + queue reports :ref:`V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS` capability.
> + Old drivers and applications must set it to zero.
Drop the 'Valid only' sentence. The V4L2_FLAG_MEMORY_NON_CONSISTENT depends
on that capability, but other flags added in the future may not.
Inside add a reference to the memory flags section created in patch 3.
> +
> +
> + * - __u32
> + - ``reserved``\ [6]
> - A place holder for future extensions. Drivers and applications
> must set the array to zero.
>
> diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> index d0c643db477a..9741dac0d5b3 100644
> --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> @@ -112,10 +112,19 @@ 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. Valid only when
> + queue reports :ref:`V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS` capability.
Same comment as above.
> + Old drivers and applications must set it to zero.
> +
> + * -
> + - __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}|
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 7cdfcd1baf82..eb5d1306cb03 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -707,9 +707,15 @@ 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);
>
> @@ -738,6 +744,7 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
> unsigned requested_sizes[VIDEO_MAX_PLANES];
> struct v4l2_format *f = &create->format;
> int ret = vb2_verify_memory_type(q, create->memory, f->type);
> + bool consistent = true;
> unsigned i;
>
> fill_buf_caps(q, &create->capabilities);
> @@ -783,7 +790,11 @@ 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, true,
> +
> + if (create->flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
> + consistent = false;
> +
> + return ret ? ret : vb2_core_create_bufs(q, create->memory, consistent,
> &create->count, requested_planes, requested_sizes);
> }
> EXPORT_SYMBOL_GPL(vb2_create_bufs);
> @@ -953,13 +964,17 @@ 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 aaf83e254272..9791e2882382 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);
> }
>
> @@ -2015,7 +2012,7 @@ 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);
>
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 72efc1c544cd..169a8cf345ed 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -938,7 +938,10 @@ 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];
> + };
How about this:
__u8 flags;
__u8 reserved[3];
That avoids the anonymous union and allows some space for future additions.
Regards,
Hans
> };
>
> /* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */
> @@ -2445,7 +2448,8 @@ struct v4l2_create_buffers {
> __u32 memory;
> struct v4l2_format format;
> __u32 capabilities;
> - __u32 reserved[7];
> + __u32 flags;
> + __u32 reserved[6];
> };
>
> /*
>
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