Re: [PATCH] pwc: do not block in VIDIOC_DQBUF

From: Andrea <audetto@tiscali.it>
To: video4linux-list@redhat.com
Subject: Re: [PATCH] pwc: do not block in VIDIOC_DQBUF
Date: Mon, 07 Jul 2008 21:21:17 +0100	[thread overview]
Message-ID: <48727ABD.40608@tiscali.it> (raw)
In-Reply-To: <25500277.1215264222465.JavaMail.root@ps10>

audetto@tiscali.it wrote:
> I think the ioctl VIDIOC_DQBUF in pwc does not follow the API spec.
> It should not block if there are no buffers and the device has been 
> opened with O_NONBLOCK.
> 
> I am not sure the patch is 100% correct, since I do not understand it 
> completely.
> 
> Andrea

Anybody to review this patch?

The documentation of VIDIOC_DQBUF is at

http://www.linuxtv.org/downloads/video4linux/API/V4L2_API/spec/r8849.htm

diff -r 87aa6048e718 linux/drivers/media/video/pwc/pwc-v4l.c

--- a/linux/drivers/media/video/pwc/pwc-v4l.c   Wed Jul 02 08:59:38 2008 -0300
+++ b/linux/drivers/media/video/pwc/pwc-v4l.c   Mon Jul 07 21:17:49 2008 +0100
@@ -1134,6 +1136,13 @@
                                      frameq is safe now.
                          */
                         add_wait_queue(&pdev->frameq, &wait);
+
+                       if ((pdev->full_frames == NULL) && (file->f_flags & O_NONBLOCK)) {
+                               remove_wait_queue(&pdev->frameq, &wait);
+                               set_current_state(TASK_RUNNING);
+                               return -EAGAIN;
+                       }
+
                         while (pdev->full_frames == NULL) {
                                 if (pdev->error_status) {
                                         remove_wait_queue(&pdev->frameq, &wait);


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