Re: Does get_user_pages_fast lock the user pages in memory in my case?

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> http://v4l2spec.bytesex.org/spec/r13696.htm
> shows the vidioc_reqbufs(). It determines the method of IO : "Memory 
> Mapping or User Pointer I/O"
> 
> The application developers can support any methodes of the Two, there is 
> no mandatory request to realize
> both methods.   For example, the Mplayer only support the "memory 
> maping" method ,and it does't support the "user pointer",
> while the VLC supports both.

I greped VIDIOC_REQBUFS on current tree.
Almost driver has following check.

        if (rb->memory != V4L2_MEMORY_MMAP)
		return -EINVAL;

IOW, almost one don't provide V4L2_MEMORY_USERPTR method.
Thus, I think any userland application don't want use V4L2_MEMORY_USERPTR.
I recommend you also return -EINVAL.

I think we can't implement V4L2_MEMORY_USERPTR properly.
it is mistake by specification.




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