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Subject: Re: [PATCHv4 04/11] videobuf2: add queue memory consistency parameter
To:     Sergey Senozhatsky <senozhatsky@chromium.org>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Tomasz Figa <tfiga@chromium.org>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Sakari Ailus <sakari.ailus@iki.fi>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Pawel Osciak <posciak@chromium.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200302041213.27662-1-senozhatsky@chromium.org>
 <20200302041213.27662-5-senozhatsky@chromium.org>
From:   Hans Verkuil <hverkuil@xs4all.nl>
Message-ID: <7ab74b32-441d-1a1a-0112-6c4d0c0b900c@xs4all.nl>
Date:   Fri, 6 Mar 2020 15:04:47 +0100
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On 02/03/2020 05:12, Sergey Senozhatsky wrote:
> Preparations for future V4L2_FLAG_MEMORY_NON_CONSISTENT support.
> 
> Extend vb2_core_reqbufs() with queue memory consistency flag
> that is applied to the newly allocated buffers.
> 
> An attempt to allocate a buffer with consistency requirements
> which don't match queue's consistency model will fail.
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  .../media/common/videobuf2/videobuf2-core.c   | 47 +++++++++++++++----
>  .../media/common/videobuf2/videobuf2-v4l2.c   |  6 +--
>  drivers/media/dvb-core/dvb_vb2.c              |  2 +-
>  include/media/videobuf2-core.h                |  7 ++-
>  4 files changed, 47 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 4489744fbbd9..3ca0545db7ee 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -664,8 +664,19 @@ 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)
> +{
> +	if (!vb2_queue_allows_cache_hints(q))
> +		return;
> +
> +	if (consistent_mem)
> +		q->dma_attrs &= ~DMA_ATTR_NON_CONSISTENT;
> +	else
> +		q->dma_attrs |= DMA_ATTR_NON_CONSISTENT;
> +}
> +
>  int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> -		unsigned int *count)
> +		bool consistent_mem, unsigned int *count)
>  {
>  	unsigned int num_buffers, allocated_buffers, num_planes = 0;
>  	unsigned plane_sizes[VB2_MAX_PLANES] = { };
> @@ -720,6 +731,7 @@ 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.
> @@ -803,9 +815,21 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_reqbufs);
>  
> +static bool verify_consistency_attr(struct vb2_queue *q, bool consistent_mem)
> +{
> +	bool queue_attr = q->dma_attrs & DMA_ATTR_NON_CONSISTENT;
> +
> +	if (consistent_mem != queue_attr) {

This is the wrong way around!

It's much better to write it like this:

       bool queue_is_consistent = !(q->dma_attrs & DMA_ATTR_NON_CONSISTENT);

       if (consistent_mem != queue_is_consistent) {

What concerns me more is that this means that this series has not been
tested properly. I found this when testing with v4l2-compliance and vivid.

I'll reply to the cover letter with more information about what needs to be
done before I merge this.

> +		dprintk(1, "memory consistency model mismatch\n");
> +		return false;
> +	}
> +	return true;
> +}
> +
>  int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> -		unsigned int *count, unsigned requested_planes,
> -		const unsigned requested_sizes[])
> +			 bool consistent_mem, unsigned int *count,
> +			 unsigned requested_planes,
> +			 const unsigned requested_sizes[])

Use 'unsigned int' in the two lines above, as per checkpatch suggestion.

Regards,

	Hans

>  {
>  	unsigned int num_planes = 0, num_buffers, allocated_buffers;
>  	unsigned plane_sizes[VB2_MAX_PLANES] = { };
> @@ -823,10 +847,15 @@ 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(1, "memory model mismatch\n");
> -		return -EINVAL;
> +	} else {
> +		if (q->memory != memory) {
> +			dprintk(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);
> @@ -2498,7 +2527,7 @@ 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, &fileio->count);
> +	ret = vb2_core_reqbufs(q, fileio->memory, true, &fileio->count);
>  	if (ret)
>  		goto err_kfree;
>  
> @@ -2555,7 +2584,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>  
>  err_reqbufs:
>  	fileio->count = 0;
> -	vb2_core_reqbufs(q, fileio->memory, &fileio->count);
> +	vb2_core_reqbufs(q, fileio->memory, true, &fileio->count);
>  
>  err_kfree:
>  	q->fileio = NULL;
> @@ -2575,7 +2604,7 @@ 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, &fileio->count);
> +		vb2_core_reqbufs(q, fileio->memory, true, &fileio->count);
>  		kfree(fileio);
>  		dprintk(3, "file io emulator closed\n");
>  	}
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index c847bcea6e95..6111d74f68c9 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -724,7 +724,7 @@ 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, &req->count);
> +	return ret ? ret : vb2_core_reqbufs(q, req->memory, true, &req->count);
>  }
>  EXPORT_SYMBOL_GPL(vb2_reqbufs);
>  
> @@ -798,7 +798,7 @@ 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,
> +	return ret ? ret : vb2_core_create_bufs(q, create->memory, true,
>  		&create->count, requested_planes, requested_sizes);
>  }
>  EXPORT_SYMBOL_GPL(vb2_create_bufs);
> @@ -974,7 +974,7 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
>  		return res;
>  	if (vb2_queue_is_busy(vdev, file))
>  		return -EBUSY;
> -	res = vb2_core_reqbufs(vdev->queue, p->memory, &p->count);
> +	res = vb2_core_reqbufs(vdev->queue, p->memory, true, &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/dvb-core/dvb_vb2.c b/drivers/media/dvb-core/dvb_vb2.c
> index 6974f1731529..e60063652164 100644
> --- a/drivers/media/dvb-core/dvb_vb2.c
> +++ b/drivers/media/dvb-core/dvb_vb2.c
> @@ -342,7 +342,7 @@ int dvb_vb2_reqbufs(struct dvb_vb2_ctx *ctx, struct dmx_requestbuffers *req)
>  
>  	ctx->buf_siz = req->size;
>  	ctx->buf_cnt = req->count;
> -	ret = vb2_core_reqbufs(&ctx->vb_q, VB2_MEMORY_MMAP, &req->count);
> +	ret = vb2_core_reqbufs(&ctx->vb_q, VB2_MEMORY_MMAP, true, &req->count);
>  	if (ret) {
>  		ctx->state = DVB_VB2_STATE_NONE;
>  		dprintk(1, "[%s] count=%d size=%d errno=%d\n", ctx->name,
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 731fd9fbd506..ba83ac754c21 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -737,6 +737,7 @@ void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb);
>   * vb2_core_reqbufs() - Initiate streaming.
>   * @q:		pointer to &struct vb2_queue with videobuf2 queue.
>   * @memory:	memory type, as defined by &enum vb2_memory.
> + * @consistent_mem:	memory consistency model.
>   * @count:	requested buffer count.
>   *
>   * Videobuf2 core helper to implement VIDIOC_REQBUF() operation. It is called
> @@ -761,12 +762,13 @@ void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb);
>   * Return: returns zero on success; an error code otherwise.
>   */
>  int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> -		unsigned int *count);
> +		bool consistent_mem, unsigned int *count);
>  
>  /**
>   * vb2_core_create_bufs() - Allocate buffers and any required auxiliary structs
>   * @q: pointer to &struct vb2_queue with videobuf2 queue.
>   * @memory: memory type, as defined by &enum vb2_memory.
> + * @consistent_mem: memory consistency model.
>   * @count: requested buffer count.
>   * @requested_planes: number of planes requested.
>   * @requested_sizes: array with the size of the planes.
> @@ -784,7 +786,8 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>   * Return: returns zero on success; an error code otherwise.
>   */
>  int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> -			 unsigned int *count, unsigned int requested_planes,
> +			 bool consistent_mem, unsigned int *count,
> +			 unsigned int requested_planes,
>  			 const unsigned int requested_sizes[]);
>  
>  /**
>