On Fri, 17 Apr 2009 19:55:29 -0700 (PDT)
Linus Torvalds <[email protected]> wrote:

> @@ -742,7 +742,7 @@ static int uvc_alloc_urb_buffers(struct
> > uvc_video_device *video, 
> >     /* Buffers are already allocated, bail out. */
> >     if (video->urb_size)
> > -           return 0;
> > +           return DIV_ROUND_UP(video->urb_size, psize);
> 
> I don't think this is right. It should round _down_.
> 
> It's supposed to return 'npackets', but if you pass it a different
> packet size than it was passed originally, it can now return a

Now uvc only uses the previous allocated buffer in suspend/resume
path, so the packet size doen't change in this path.

> potentially bigger number than the already allocated buffer, no?

If this case does exist, the URBs need to be updated and the patch is 
not enough. 

> 
> So I think it should round down (ie use a regular divide). No?

Because the following fact:

        uvc_alloc_urb_buffers()
        {
                ...
                video->urb_size = psize * npackets; 
                ...
        }

so DIV_ROUND_UP still can work correctly.

Thanks!

-- 
Lei Ming
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