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SubjectRe: [PATCH] dma-buf: add DMA_BUF_IOCTL_SYNC_PARTIAL support
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Am 13.11.21 um 07:22 schrieb Jianqun Xu:
> Add DMA_BUF_IOCTL_SYNC_PARTIAL support for user to sync dma-buf with
> offset and len.

You have not given an use case for this so it is a bit hard to review.
And from the existing use cases I don't see why this should be necessary.

Even worse from the existing backend implementation I don't even see how
drivers should be able to fulfill this semantics.

Please explain further,
Christian.

>
> Change-Id: I03d2d2e10e48d32aa83c31abade57e0931e1be49
> Signed-off-by: Jianqun Xu <jay.xu@rock-chips.com>
> ---
> drivers/dma-buf/dma-buf.c | 42 ++++++++++++++++++++++++++++++++++++
> include/uapi/linux/dma-buf.h | 8 +++++++
> 2 files changed, 50 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index d9948d58b3f4..78f37f7c3462 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -392,6 +392,7 @@ static long dma_buf_ioctl(struct file *file,
> {
> struct dma_buf *dmabuf;
> struct dma_buf_sync sync;
> + struct dma_buf_sync_partial sync_p;
> enum dma_data_direction direction;
> int ret;
>
> @@ -430,6 +431,47 @@ static long dma_buf_ioctl(struct file *file,
> case DMA_BUF_SET_NAME_B:
> return dma_buf_set_name(dmabuf, (const char __user *)arg);
>
> + case DMA_BUF_IOCTL_SYNC_PARTIAL:
> + if (copy_from_user(&sync_p, (void __user *) arg, sizeof(sync_p)))
> + return -EFAULT;
> +
> + if (sync_p.len == 0)
> + return 0;
> +
> + if ((sync_p.offset % cache_line_size()) || (sync_p.len % cache_line_size()))
> + return -EINVAL;
> +
> + if (sync_p.len > dmabuf->size || sync_p.offset > dmabuf->size - sync_p.len)
> + return -EINVAL;
> +
> + if (sync_p.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
> + return -EINVAL;
> +
> + switch (sync_p.flags & DMA_BUF_SYNC_RW) {
> + case DMA_BUF_SYNC_READ:
> + direction = DMA_FROM_DEVICE;
> + break;
> + case DMA_BUF_SYNC_WRITE:
> + direction = DMA_TO_DEVICE;
> + break;
> + case DMA_BUF_SYNC_RW:
> + direction = DMA_BIDIRECTIONAL;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + if (sync_p.flags & DMA_BUF_SYNC_END)
> + ret = dma_buf_end_cpu_access_partial(dmabuf, direction,
> + sync_p.offset,
> + sync_p.len);
> + else
> + ret = dma_buf_begin_cpu_access_partial(dmabuf, direction,
> + sync_p.offset,
> + sync_p.len);
> +
> + return ret;
> +
> default:
> return -ENOTTY;
> }
> diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h
> index 7f30393b92c3..6236c644624d 100644
> --- a/include/uapi/linux/dma-buf.h
> +++ b/include/uapi/linux/dma-buf.h
> @@ -47,4 +47,12 @@ struct dma_buf_sync {
> #define DMA_BUF_SET_NAME_A _IOW(DMA_BUF_BASE, 1, u32)
> #define DMA_BUF_SET_NAME_B _IOW(DMA_BUF_BASE, 1, u64)
>
> +struct dma_buf_sync_partial {
> + __u64 flags;
> + __u32 offset;
> + __u32 len;
> +};
> +
> +#define DMA_BUF_IOCTL_SYNC_PARTIAL _IOW(DMA_BUF_BASE, 2, struct dma_buf_sync_partial)
> +
> #endif

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