oss-redir/libaoss doesn't set blocked IO correctly [PATCH]

oss-redir/libaoss doesn't set blocked IO correctly [PATCH]

[Matthew Hodgson]

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Hi,

I'm investigating switching videolan's OSS-style audio-capture (used to 
complement streaming from a v4l source) to use the alsa-oss oss-redir 
abstraction layer.  Whilst writing the patch, I came up against the 
quirk that

i_fd = oss_pcm_open(devname, O_RDONLY | O_NONBLOCK)

doesn't return a non-blocking file descriptor.  This is a bit of a 
showstopper, as vlc relies on the fd being nonblocking in order for the 
thread to yield to allow interleaved video capture to occur.

The problem appears to be a typo in alsa-oss/alsa/pcm.c:oss_dsp_open(), 
where the mode parameter rather than the oflags parameter is checked for 
the O_NONBLOCK flag.  I've included a trivial patch to fix it.

cheers;

M.

-- 
______________________________________________________________
Matthew Hodgson   matthew@mxtelecom.com   Tel: +44 845 6667778
                 Systems Analyst, MX Telecom Ltd.

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Index: pcm.c
===================================================================
RCS file: /cvsroot/alsa/alsa-oss/alsa/pcm.c,v
retrieving revision 1.19
diff -u -r1.19 pcm.c
--- pcm.c       27 Dec 2004 19:25:47 -0000      1.19
+++ pcm.c       19 Mar 2005 14:43:04 -0000
@@ -534,7 +534,7 @@
                errno = ENOENT;
                return -1;
        }
-       if (mode & O_NONBLOCK)
+       if (oflag & O_NONBLOCK)
                pcm_mode = SND_PCM_NONBLOCK;
        switch (oflag & O_ACCMODE) {
        case O_RDONLY:

Re: oss-redir/libaoss doesn't set blocked IO correctly [PATCH]

[Jaroslav Kysela]

On Sat, 19 Mar 2005, Matthew Hodgson wrote:

> Hi,
> 
> I'm investigating switching videolan's OSS-style audio-capture (used to 
> complement streaming from a v4l source) to use the alsa-oss oss-redir 
> abstraction layer.  Whilst writing the patch, I came up against the 
> quirk that
> 
> i_fd = oss_pcm_open(devname, O_RDONLY | O_NONBLOCK)
> 
> doesn't return a non-blocking file descriptor.  This is a bit of a 
> showstopper, as vlc relies on the fd being nonblocking in order for the 
> thread to yield to allow interleaved video capture to occur.
> 
> The problem appears to be a typo in alsa-oss/alsa/pcm.c:oss_dsp_open(), 
> where the mode parameter rather than the oflags parameter is checked for 
> the O_NONBLOCK flag.  I've included a trivial patch to fix it.

Applied. Thanks.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs


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