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Subject: Re: [PATCHv3 7/8] videobuf2: handle V4L2_MEMORY_FLAG_NON_COHERENT
 flag
To:     Sergey Senozhatsky <senozhatsky@chromium.org>,
        Tomasz Figa <tfiga@chromium.org>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc:     Ricardo Ribalda <ribalda@chromium.org>,
        Christoph Hellwig <hch@lst.de>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Collabora Kernel ML <kernel@collabora.com>
References: <20210709092027.1050834-1-senozhatsky@chromium.org>
 <20210709092027.1050834-8-senozhatsky@chromium.org>
From:   Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Message-ID: <0c89ef1e-8abb-8749-bbce-c7e5a2e2f304@collabora.com>
Date:   Thu, 22 Jul 2021 19:33:24 +0200
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On 09.07.21 11:20, Sergey Senozhatsky wrote:
> This patch lets user-space to request a non-coherent 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 byte of a 4 byte ->reserved[1] member of struct
>   v4l2_requestbuffers. The struct, thus, now has reserved 3 bytes.
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>   .../media/v4l/vidioc-create-bufs.rst          |  7 ++++-
>   .../media/v4l/vidioc-reqbufs.rst              | 11 ++++---
>   .../media/common/videobuf2/videobuf2-core.c   |  4 +--
>   .../media/common/videobuf2/videobuf2-v4l2.c   | 31 +++++++++++++++++--
>   drivers/media/v4l2-core/v4l2-compat-ioctl32.c |  9 +++++-
>   drivers/media/v4l2-core/v4l2-ioctl.c          |  4 +--
>   include/uapi/linux/videodev2.h                |  9 ++++--
>   7 files changed, 60 insertions(+), 15 deletions(-)
> 
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
> index f98f18c9e91c..a048a9f6b7b6 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
> @@ -113,7 +113,12 @@ than the number requested.
>   	``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.
>   
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> index e59306aba2b0..099fa6695167 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> @@ -104,10 +104,13 @@ 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
> -      - ``reserved``\ [1]
> -      - A place holder for future extensions. Drivers and applications
> -	must set the array to zero.
> +    * - __u8
> +      - ``flags``
> +      - Specifies additional buffer management attributes.
> +	See :ref:`memory-flags`.
> +    * - __u8
> +      - ``reserved``\ [3]
> +      - Reserved for future extensions.
>   
>   .. _v4l2-buf-capabilities:
>   .. _V4L2-BUF-CAP-SUPPORTS-MMAP:
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index af4db310cf5e..38505783247e 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -762,7 +762,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>   {
>   	unsigned int num_buffers, allocated_buffers, num_planes = 0;
>   	unsigned plane_sizes[VB2_MAX_PLANES] = { };
> -	bool coherent_mem = true;
> +	bool coherent_mem = !(flags & V4L2_MEMORY_FLAG_NON_COHERENT);
>   	unsigned int i;
>   	int ret;
>   
> @@ -906,7 +906,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>   {
>   	unsigned int num_planes = 0, num_buffers, allocated_buffers;
>   	unsigned plane_sizes[VB2_MAX_PLANES] = { };
> -	bool coherent_mem = true;
> +	bool coherent_mem = !(flags & V4L2_MEMORY_FLAG_NON_COHERENT);
>   	int ret;
>   
>   	if (q->num_buffers == VB2_MAX_FRAME) {
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index b4f70ddb09b0..6edf4508c636 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -692,12 +692,32 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
>   #endif
>   }
>   
> +static void validate_memory_flags(struct vb2_queue *q,
> +				  int memory,
> +				  u32 *flags)
> +{
> +	if (!q->allow_cache_hints || memory != V4L2_MEMORY_MMAP) {
> +		/*
> +		 * This needs to clear V4L2_MEMORY_FLAG_NON_COHERENT only,
> +		 * but in order to avoid bugs we zero out all bits.
> +		 */
> +		*flags = 0;
> +	} else {
> +		/* Clear all unknown flags. */
> +		*flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
> +	}
> +}
> +
>   int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
>   {
>   	int ret = vb2_verify_memory_type(q, req->memory, req->type);
> +	u32 flags = req->flags;
>   
>   	fill_buf_caps(q, &req->capabilities);
> -	return ret ? ret : vb2_core_reqbufs(q, req->memory, 0, &req->count);
> +	validate_memory_flags(q, req->memory, &flags);
> +	req->flags = flags;

you can do instead

validate_memory_flags(q, req->memory, &req->flags);

> +	return ret ? ret : vb2_core_reqbufs(q, req->memory,
> +					    req->flags, &req->count);
>   }
>   EXPORT_SYMBOL_GPL(vb2_reqbufs);
>   
> @@ -729,6 +749,7 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
>   	unsigned i;
>   
>   	fill_buf_caps(q, &create->capabilities);
> +	validate_memory_flags(q, create->memory, &create->flags);
>   	create->index = q->num_buffers;
>   	if (create->count == 0)
>   		return ret != -EBUSY ? ret : 0;
> @@ -772,7 +793,7 @@ 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,
> -						0,
> +						create->flags,
>   						&create->count,
>   						requested_planes,
>   						requested_sizes);
> @@ -969,13 +990,16 @@ 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);
> +	u32 flags = p->flags;
>   
>   	fill_buf_caps(vdev->queue, &p->capabilities);
> +	validate_memory_flags(vdev->queue, p->memory, &flags);
> +	p->flags = flags;

ditto


thanks,
Dafna

>   	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)
> @@ -993,6 +1017,7 @@ int vb2_ioctl_create_bufs(struct file *file, void *priv,
>   
>   	p->index = vdev->queue->num_buffers;
>   	fill_buf_caps(vdev->queue, &p->capabilities);
> +	validate_memory_flags(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.
> diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> index 47aff3b19742..8176769a89fa 100644
> --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> @@ -126,6 +126,9 @@ 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 {
> @@ -134,7 +137,8 @@ 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 get_v4l2_format32(struct v4l2_format *p64,
> @@ -182,6 +186,8 @@ static int get_v4l2_create32(struct v4l2_create_buffers *p64,
>   	if (copy_from_user(p64, p32,
>   			   offsetof(struct v4l2_create_buffers32, format)))
>   		return -EFAULT;
> +	if (copy_from_user(&p64->flags, &p32->flags, sizeof(p32->flags)))
> +		return -EFAULT;
>   	return get_v4l2_format32(&p64->format, &p32->format);
>   }
>   
> @@ -227,6 +233,7 @@ static int put_v4l2_create32(struct v4l2_create_buffers *p64,
>   	if (copy_to_user(p32, p64,
>   			 offsetof(struct v4l2_create_buffers32, format)) ||
>   	    put_user(p64->capabilities, &p32->capabilities) ||
> +	    put_user(p64->flags, &p32->flags) ||
>   	    copy_to_user(p32->reserved, p64->reserved, sizeof(p64->reserved)))
>   		return -EFAULT;
>   	return put_v4l2_format32(&p64->format, &p32->format);
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 05d5db3d85e5..6a941da33998 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -2004,7 +2004,7 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>   	if (ret)
>   		return ret;
>   
> -	CLEAR_AFTER_FIELD(p, capabilities);
> +	CLEAR_AFTER_FIELD(p, flags);
>   
>   	return ops->vidioc_reqbufs(file, fh, p);
>   }
> @@ -2045,7 +2045,7 @@ 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 9d11e1d9c934..7973aa0465d2 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -953,7 +953,8 @@ struct v4l2_requestbuffers {
>   	__u32			type;		/* enum v4l2_buf_type */
>   	__u32			memory;		/* enum v4l2_memory */
>   	__u32			capabilities;
> -	__u32			reserved[1];
> +	__u8			flags;
> +	__u8			reserved[3];
>   };
>   
>   #define V4L2_MEMORY_FLAG_NON_COHERENT			(1 << 0)
> @@ -2501,6 +2502,9 @@ 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 {
> @@ -2509,7 +2513,8 @@ struct v4l2_create_buffers {
>   	__u32			memory;
>   	struct v4l2_format	format;
>   	__u32			capabilities;
> -	__u32			reserved[7];
> +	__u32			flags;
> +	__u32			reserved[6];
>   };
>   
>   /*
>