Messages in this thread | | | From | Laurent Pinchart <> | Subject | Re: [PATCH v3] media: usb: uvc: use vb2_ops_wait_prepare/finish helper | Date | Sat, 29 Nov 2014 20:11:41 +0200 |
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Hi Prabhakar,
On Friday 28 November 2014 17:06:52 Prabhakar Lad wrote: > On Thu, Nov 27, 2014 at 9:32 PM, Laurent Pinchart wrote: > > Hi Prabhakar, > > [Snip] > > >> + queue->queue.lock = &queue->mutex; > > > > I'm a bit concerned that this would introduce future breakages. Setting > > the queue.lock pointer enables locking in all vb2_fop_* and vb2_ops_wait_* > > functions. The uvcvideo driver isn't ready for that, but doesn't use the > > vb2_fop_* functions yet, so that's not an issue. However, in the future, > > videobuf2 might use the lock in more places, including functions used by > > the uvcvideo driver. This could then cause breakages. > > Even if in future if videobuf2 uses this lock it would be in helpers mostly, > so any way it doesn’t harm :)
My concern is about vb2 starting using the lock in existing helpers used by the uvcvideo driver. I suppose we can deal with it later.
> > It would be better to completely convert the uvcvideo driver to the > > vb2_fop_* functions if we want to use vb2_ops_*. I'm not sure how complex > > that would be though, and whether it would be possible while still > > keeping the fine-grained locking implemented by the uvcvideo driver. Do > > you think it should be attempted ? > > mmap & poll should be fairly simple, looks like open & release cannot be > dropped as it does some usb_autopm_get/put_interface() calls which I am not > aware of.
I've looked at that, and there's a race condition in vb2_fop_poll() (for which I've already sent a patch) and possible in vb2_mmap() (raised the issue on #v4l today) as well that need to be fixed first.
Anyway, for this patch
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Have you tested it by the way ?
Should I take it in my tree or will you send a pull request for the whole series ?
> >> ret = vb2_queue_init(&queue->queue); > >> if (ret) > >> return ret;
-- Regards,
Laurent Pinchart
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