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Date: Sun, 7 Apr 2024 15:50:10 +0800
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Subject: Re: [PATCH] dma-buf: add DMA_BUF_IOCTL_SYNC_PARTIAL support
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To: =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
 Jianqun Xu <jay.xu@rock-chips.com>, sumit.semwal@linaro.org
Cc: pekka.paalanen@collabora.com, daniel.vetter@ffwll.ch,
 jason@jlekstrand.net, linux-media@vger.kernel.org,
 dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org,
 linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org
References: <20211113062222.3743909-1-jay.xu@rock-chips.com>
 <1da5cdf0-ccb8-3740-cf96-794c4d5b2eb4@amd.com>
From: Rong Qianfeng <rongqianfeng@vivo.com>
In-Reply-To: <1da5cdf0-ccb8-3740-cf96-794c4d5b2eb4@amd.com>
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在 2021/11/15 19:42, Christian König 写道:
> 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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> Subject: Re: [PATCH] dma-buf: add DMA_BUF_IOCTL_SYNC_PARTIAL support
> To: Jianqun Xu <jay.xu@rock-chips.com>, sumit.semwal@linaro.org
> References: <20211113062222.3743909-1-jay.xu@rock-chips.com>
> From: =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
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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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> Subject: Re: [PATCH] dma-buf: add DMA_BUF_IOCTL_SYNC_PARTIAL support
> To: Jianqun Xu <jay.xu@rock-chips.com>, sumit.semwal@linaro.org
> Cc: pekka.paalanen@collabora.com, daniel.vetter@ffwll.ch,
> jason@jlekstrand.net, linux-media@vger.kernel.org,
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> From: =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
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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.
Here is a practical case:
The user space can allocate a large chunk of dma-buf for 
self-management, used as a shared memory pool.
Small dma-buf can be allocated from this shared memory pool and released 
back to it after use, thus improving the speed of dma-buf allocation and 
release.
Additionally, custom functionalities such as memory statistics and 
boundary checking can be implemented in the user space.
Of course, the above-mentioned functionalities require the 
implementation of a partial cache sync interface.

Thanks
Rong Qianfeng.
>
>>
>> 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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