On 04/06/2012 03:29 PM, Laurent Pinchart wrote:
> Hi Tomasz,
>
> On Thursday 05 April 2012 16:00:00 Tomasz Stanislawski wrote:
>> From: Sumit Semwal <sumit.sem...@ti.com>
>>
>> This patch adds support for DMABUF memory type in videobuf2. It calls
>> relevant APIs of dma_buf for v4l reqbuf / qbuf / dqbuf operations.
>>
>> For this version, the support is for videobuf2 as a user of the shared
>> buffer; so the allocation of the buffer is done outside of V4L2. [A sample
>> allocator of dma-buf shared buffer is given at [1]]
>>
>> [1]: Rob Clark's DRM:
>> https://github.com/robclark/kernel-omap4/commits/drmplane-dmabuf
>>
>> Signed-off-by: Tomasz Stanislawski <t.stanisl...@samsung.com>
>> [original work in the PoC for buffer sharing]
>> Signed-off-by: Sumit Semwal <sumit.sem...@ti.com>
>> Signed-off-by: Sumit Semwal <sumit.sem...@linaro.org>
>> ---
>> drivers/media/video/videobuf2-core.c | 184 ++++++++++++++++++++++++++++++-
>> include/media/videobuf2-core.h | 31 ++++++
>> 2 files changed, 214 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/media/video/videobuf2-core.c
>> b/drivers/media/video/videobuf2-core.c index 2e8f1df..b37feea 100644
>> --- a/drivers/media/video/videobuf2-core.c
>> +++ b/drivers/media/video/videobuf2-core.c
>
> [snip]
>
>> @@ -451,6 +482,21 @@ static int __verify_mmap_ops(struct vb2_queue *q)
>> }
>>
>> /**
>> + * __verify_dmabuf_ops() - verify that all memory operations required for
>> + * DMABUF queue type have been provided
>> + */
>> +static int __verify_dmabuf_ops(struct vb2_queue *q)
>> +{
>> + if (!(q->io_modes & VB2_DMABUF) || !q->mem_ops->attach_dmabuf
>> + || !q->mem_ops->detach_dmabuf
>> + || !q->mem_ops->map_dmabuf
>> + || !q->mem_ops->unmap_dmabuf)
>
> That's pretty strange indentation. What about
>
> if (!(q->io_modes & VB2_DMABUF) || !q->mem_ops->attach_dmabuf ||
> !q->mem_ops->detach_dmabuf || !q->mem_ops->map_dmabuf ||
> !q->mem_ops->unmap_dmabuf)
>
ok
>> + return -EINVAL;
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> * vb2_reqbufs() - Initiate streaming
>> * @q: videobuf2 queue
>> * @req: struct passed from userspace to vidioc_reqbufs handler in driver
>> @@ -484,6 +530,7 @@ int vb2_reqbufs(struct vb2_queue *q, struct
>> v4l2_requestbuffers *req) }
>>
>> if (req->memory != V4L2_MEMORY_MMAP
>> + && req->memory != V4L2_MEMORY_DMABUF
>> && req->memory != V4L2_MEMORY_USERPTR) {
>> dprintk(1, "reqbufs: unsupported memory type\n");
>> return -EINVAL;
>
> Ditto.
>
> [snip]
>
>> @@ -620,7 +672,8 @@ int vb2_create_bufs(struct vb2_queue *q, struct
>> v4l2_create_buffers *create) }
>>
>> if (create->memory != V4L2_MEMORY_MMAP
>> - && create->memory != V4L2_MEMORY_USERPTR) {
>> + && create->memory != V4L2_MEMORY_USERPTR
>> + && create->memory != V4L2_MEMORY_DMABUF) {
>> dprintk(1, "%s(): unsupported memory type\n", __func__);
>> return -EINVAL;
>> }
>
> And here too.
>
> [snip]
>
>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>> index a15d1f1..665e846 100644
>> --- a/include/media/videobuf2-core.h
>> +++ b/include/media/videobuf2-core.h
>
> [snip]
>
>> @@ -65,6 +82,17 @@ struct vb2_mem_ops {
>> unsigned long size, int write);
>> void (*put_userptr)(void *buf_priv);
>>
>> + /*
>> + * Comment from Rob Clark: XXX: I think the attach / detach could be
>> + * handled in the vb2 core, and vb2_mem_ops really just need to get/put
>> + * the sglist (and make sure that the sglist fits it's needs..)
>> + */
>
> I think we should address this now. We've previously discussed the question,
> but haven't reached an agreement.
>
> Quoting my reply to "[RFCv2 PATCH 3/9] v4l: vb2: Add dma-contig allocator as
> dma_buf user" on 28/03/2012:
>
>>> Calling dma_buf_attach could be moved to vb2-core. But it gives little
>>> gain. First, the pointer of dma_buf_attachment would have to be added to
>>> struct vb2_plane. Second, the allocator would have to keep in the copy of
>>> this pointer in its context structure for use of vb2_dc_(un)map_dmabuf
>>> functions.
>>
>> Right. Would it make sense to pass the vb2_plane pointer, or possibly the
>> dma_buf_attachment pointer, to the mmap_dmabuf and unmap_dmabuf operations ?
>>
>>> Third, dma_buf_attach requires a pointer to 'struct device' which is not
>>> available in the vb2-core layer.
>>
>> OK, that's a problem.
>>
>>> Because of the mentioned reasons I decided to keep attach_dmabuf in
>>> allocator-specific code.
>>
>> Maybe it would make sense to create a vb2_mem_buf structure from which
>> vb2_dc_buf (and other allocator-specific buffer descriptors) would inherit ?
>> That structure would store the dma_buf_attach pointer, and common dma-buf
>> code could be put in videobuf2-memops.c and shared between allocators. Just
>> an idea.
>
> If we find out that the best course of action is to leave the code as-is, we
> should remove the above comment.
>
Ok. Adding support for VIVI introduces new problem. This driver is not
associated
with any struct device. Therefore attach_dmabuf for vmalloc allocator must not
call dma_buf_attach because this call fails if the device is NULL.
Hiding (non)calling dma_buf_attach inside allocator code really helps.
>> + void *(*attach_dmabuf)(void *alloc_ctx, struct dma_buf *dbuf,
>> + unsigned long size, int write);
>> + void (*detach_dmabuf)(void *buf_priv);
>> + int (*map_dmabuf)(void *buf_priv);
>> + void (*unmap_dmabuf)(void *buf_priv);
>> +
>> void *(*vaddr)(void *buf_priv);
>> void *(*cookie)(void *buf_priv);
>
Regards,
Tomasz Stanislawski
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