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mdev: sound is only working some of the time.

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acm at muc

Mar 20, 2012, 3:31 PM

Post #1 of 11 (522 views)
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mdev: sound is only working some of the time.

Hi, all.

Got a problem with my system running under mdev. When I try to play CDs
(with aqualung feeding into PulseAudio), no sound comes out. However,
when I listen to an audio section from a newspaper page such as
www.tagesschau.de (no idea what audio format) it works.

Clearly this is something to do with mdev. I had a look at the devices
in /dev, searching for those in group audio. Under udev, I find the
following as device nodes:

adsp audio dsp mixer mixer1 sequencer sequencer2.

Under mdev, all of these bar one are symlinks into the real nodes in a
subdirectory. The odd man out is mixer1 which is a device node, but
with owner/group begin root/root (rather than root/audio).

Can anybody suggest any fix, or further areas of exploration? Thanks!

--
Alan Mackenzie (Nuremberg, Germany).

w41ter at gmail

Mar 20, 2012, 4:23 PM

Post #2 of 11 (515 views)
Permalink

Re: mdev: sound is only working some of the time. [In reply to]

On 03/20/2012 03:31 PM, Alan Mackenzie wrote:
> Hi, all.
>
> Got a problem with my system running under mdev. When I try to play CDs
> (with aqualung feeding into PulseAudio), no sound comes out. However,
> when I listen to an audio section from a newspaper page such as
> www.tagesschau.de (no idea what audio format) it works.
>
> Clearly this is something to do with mdev. I had a look at the devices
> in /dev, searching for those in group audio. Under udev, I find the
> following as device nodes:
>
> adsp audio dsp mixer mixer1 sequencer sequencer2.
>
> Under mdev, all of these bar one are symlinks into the real nodes in a
> subdirectory. The odd man out is mixer1 which is a device node, but
> with owner/group begin root/root (rather than root/audio).
>
> Can anybody suggest any fix, or further areas of exploration? Thanks!

Can you do chown root:audio on the mixer as a test?

pandu at poluan

Mar 20, 2012, 5:35 PM

Post #3 of 11 (518 views)
Permalink

Re: mdev: sound is only working some of the time. [In reply to]

On Mar 21, 2012 5:36 AM, "Alan Mackenzie" <acm [at] muc> wrote:
>
> Hi, all.
>
> Got a problem with my system running under mdev. When I try to play CDs
> (with aqualung feeding into PulseAudio), no sound comes out. However,
> when I listen to an audio section from a newspaper page such as
> www.tagesschau.de (no idea what audio format) it works.
>
> Clearly this is something to do with mdev. I had a look at the devices
> in /dev, searching for those in group audio. Under udev, I find the
> following as device nodes:
>
> adsp audio dsp mixer mixer1 sequencer sequencer2.
>
> Under mdev, all of these bar one are symlinks into the real nodes in a
> subdirectory. The odd man out is mixer1 which is a device node, but
> with owner/group begin root/root (rather than root/audio).
>
> Can anybody suggest any fix, or further areas of exploration? Thanks!
>

That's indicative that it's the kernel doing the populating (that is,
everything belongs to root:root). That means, mdev hasn't got the chance to
'restructure' the /dev directory (that is, rename and/or move and/or chown
devices).

Does 'mdev -s' exist in your /sbin/linuxrc? Can you post your linuxrc here?

Rgds,

acm at muc

Mar 21, 2012, 4:11 AM

Post #4 of 11 (520 views)
Permalink

Re: Re: mdev: sound is only working some of the time. [In reply to]

Hello, Walt.

On Tue, Mar 20, 2012 at 04:23:14PM -0700, walt wrote:
> On 03/20/2012 03:31 PM, Alan Mackenzie wrote:
> > Hi, all.

> > Got a problem with my system running under mdev. When I try to play CDs
> > (with aqualung feeding into PulseAudio), no sound comes out. However,
> > when I listen to an audio section from a newspaper page such as
> > www.tagesschau.de (no idea what audio format) it works.

> > Clearly this is something to do with mdev. I had a look at the devices
> > in /dev, searching for those in group audio. Under udev, I find the
> > following as device nodes:

> > adsp audio dsp mixer mixer1 sequencer sequencer2.

> > Under mdev, all of these bar one are symlinks into the real nodes in a
> > subdirectory. The odd man out is mixer1 which is a device node, but
> > with owner/group begin root/root (rather than root/audio).

> > Can anybody suggest any fix, or further areas of exploration? Thanks!

> Can you do chown root:audio on the mixer as a test?

Done so. It didn't help. It's mightily curious why that one device is
different from the others. It's not so under udev.

Anyhow I found the problem. It was pulseaudio. I rebuilt it with its
udev use flag taken out. This didn't help.

Then I rebuilt aqualung without the pulseaudio flag, and now things work.

As I type, I am listening to Mahler's second symphony, played by the
Bamberger Symphoniker conducted by Jonathan Nott. I can recomment Mahler
for when things aren't going quite according to plan, and this recording
in particular.

--
Alan Mackenzie (Nuremberg, Germany).

acm at muc

Mar 21, 2012, 4:17 AM

Post #5 of 11 (517 views)
Permalink

Re: mdev: sound is only working some of the time. [In reply to]

Hello, Pandu.

On Wed, Mar 21, 2012 at 07:35:14AM +0700, Pandu Poluan wrote:
> On Mar 21, 2012 5:36 AM, "Alan Mackenzie" <acm [at] muc> wrote:

> > Hi, all.

> > Got a problem with my system running under mdev. When I try to play CDs
> > (with aqualung feeding into PulseAudio), no sound comes out. However,
> > when I listen to an audio section from a newspaper page such as
> > www.tagesschau.de (no idea what audio format) it works.

> > Clearly this is something to do with mdev. I had a look at the devices
> > in /dev, searching for those in group audio. Under udev, I find the
> > following as device nodes:

> > adsp audio dsp mixer mixer1 sequencer sequencer2.

> > Under mdev, all of these bar one are symlinks into the real nodes in a
> > subdirectory. The odd man out is mixer1 which is a device node, but
> > with owner/group begin root/root (rather than root/audio).

> > Can anybody suggest any fix, or further areas of exploration? Thanks!

> That's indicative that it's the kernel doing the populating (that is,
> everything belongs to root:root).

No, it was just that one device belonging to root:root. This is
mysterious indeed.

> That means, mdev hasn't got the chance to 'restructure' the /dev
> directory (that is, rename and/or move and/or chown devices).

> Does 'mdev -s' exist in your /sbin/linuxrc? Can you post your linuxrc
> here?

mdev -s wasn't in my /sbin/linuxrc. It is now. It hasn't made any
difference to that wayward device.

As I said to Walt, I've solved the problem by turfing out pulseaudio.

> Rgds,

--
Alan Mackenzie (Nuremberg, Germany).

pandu at poluan

Mar 21, 2012, 5:49 AM

Post #6 of 11 (518 views)
Permalink

Re: mdev: sound is only working some of the time. [In reply to]

On Mar 21, 2012 6:22 PM, "Alan Mackenzie" <acm [at] muc> wrote:
>
> Hello, Pandu.
>
> On Wed, Mar 21, 2012 at 07:35:14AM +0700, Pandu Poluan wrote:
> > On Mar 21, 2012 5:36 AM, "Alan Mackenzie" <acm [at] muc> wrote:
>
> > > Hi, all.
>
> > > Got a problem with my system running under mdev. When I try to play
CDs
> > > (with aqualung feeding into PulseAudio), no sound comes out. However,
> > > when I listen to an audio section from a newspaper page such as
> > > www.tagesschau.de (no idea what audio format) it works.
>
> > > Clearly this is something to do with mdev. I had a look at the
devices
> > > in /dev, searching for those in group audio. Under udev, I find the
> > > following as device nodes:
>
> > > adsp audio dsp mixer mixer1 sequencer sequencer2.
>
> > > Under mdev, all of these bar one are symlinks into the real nodes in a
> > > subdirectory. The odd man out is mixer1 which is a device node, but
> > > with owner/group begin root/root (rather than root/audio).
>
> > > Can anybody suggest any fix, or further areas of exploration? Thanks!
>
>
> > That's indicative that it's the kernel doing the populating (that is,
> > everything belongs to root:root).
>
> No, it was just that one device belonging to root:root. This is
> mysterious indeed.
>
> > That means, mdev hasn't got the chance to 'restructure' the /dev
> > directory (that is, rename and/or move and/or chown devices).
>
> > Does 'mdev -s' exist in your /sbin/linuxrc? Can you post your linuxrc
> > here?
>
> mdev -s wasn't in my /sbin/linuxrc. It is now. It hasn't made any
> difference to that wayward device.
>
> As I said to Walt, I've solved the problem by turfing out pulseaudio.
>

Strange...

Do you use mdev to handle hotplugs, btw?

Rgds,

acm at muc

Mar 21, 2012, 6:02 AM

Post #7 of 11 (513 views)
Permalink

Re: mdev: sound is only working some of the time. [In reply to]

On Wed, Mar 21, 2012 at 07:49:02PM +0700, Pandu Poluan wrote:
> On Mar 21, 2012 6:22 PM, "Alan Mackenzie" <acm [at] muc> wrote:

> > Hello, Pandu.

> > On Wed, Mar 21, 2012 at 07:35:14AM +0700, Pandu Poluan wrote:
> > > On Mar 21, 2012 5:36 AM, "Alan Mackenzie" <acm [at] muc> wrote:

> > > > Hi, all.

> > > > Got a problem with my system running under mdev. When I try to
> > > > play CDs (with aqualung feeding into PulseAudio), no sound comes
> > > > out. However, when I listen to an audio section from a newspaper
> > > > page such as www.tagesschau.de (no idea what audio format) it
> > > > works.

> > > > Clearly this is something to do with mdev. I had a look at the
> > > > devices in /dev, searching for those in group audio. Under udev,
> > > > I find the following as device nodes:

> > > > adsp audio dsp mixer mixer1 sequencer sequencer2.

> > > > Under mdev, all of these bar one are symlinks into the real nodes
> > > > in a subdirectory. The odd man out is mixer1 which is a device
> > > > node, but with owner/group begin root/root (rather than
> > > > root/audio).

> > > > Can anybody suggest any fix, or further areas of exploration?
> > > > Thanks!

> > > That's indicative that it's the kernel doing the populating (that
> > > is, everything belongs to root:root).

> > No, it was just that one device belonging to root:root. This is
> > mysterious indeed.

> > > That means, mdev hasn't got the chance to 'restructure' the /dev
> > > directory (that is, rename and/or move and/or chown devices).

> > > Does 'mdev -s' exist in your /sbin/linuxrc? Can you post your
> > > linuxrc here?

> > mdev -s wasn't in my /sbin/linuxrc. It is now. It hasn't made any
> > difference to that wayward device.

> > As I said to Walt, I've solved the problem by turfing out pulseaudio.

> Strange...

> Do you use mdev to handle hotplugs, btw?

You mean, like sticking in a USB stick, or turning my printer on? Yes, I
do.

> Rgds,

--
Alan Mackenzie (Nuremberg, Germany).

pandu at poluan

Mar 21, 2012, 6:12 AM

Post #8 of 11 (510 views)
Permalink

Re: mdev: sound is only working some of the time. [In reply to]

On Mar 21, 2012 8:07 PM, "Alan Mackenzie" <acm [at] muc> wrote:
>
> On Wed, Mar 21, 2012 at 07:49:02PM +0700, Pandu Poluan wrote:
> > Strange...
>
> > Do you use mdev to handle hotplugs, btw?
>
> You mean, like sticking in a USB stick, or turning my printer on? Yes, I
> do.
>

No, I mean, did you do :

echo /bin/mdev > /proc/sys/kernel/hotplug

(ensure beforehand that /bin/mdev is a symlink to /bin/busybox)

Rgds,

pandu at poluan

Mar 21, 2012, 6:17 AM

Post #9 of 11 (510 views)
Permalink

Re: mdev: sound is only working some of the time. [In reply to]

On Mar 21, 2012 8:07 PM, "Alan Mackenzie" <acm [at] muc> wrote:
>
> On Wed, Mar 21, 2012 at 07:49:02PM +0700, Pandu Poluan wrote:
>
> > Strange...
>
> > Do you use mdev to handle hotplugs, btw?
>
> You mean, like sticking in a USB stick, or turning my printer on? Yes, I
> do.
>

No, I mean doing this:

echo /bin/mdev > /proc/sys/kernel/hotplug

(ensure beforehand that /bin/mdev is a symlink to /bin/busybox)

Rgds,

acm at muc

Mar 21, 2012, 6:38 AM

Post #10 of 11 (516 views)
Permalink

Re: mdev: sound is only working some of the time. [In reply to]

Hello again,

On Wed, Mar 21, 2012 at 08:12:40PM +0700, Pandu Poluan wrote:
> On Mar 21, 2012 8:07 PM, "Alan Mackenzie" <acm [at] muc> wrote:

> > On Wed, Mar 21, 2012 at 07:49:02PM +0700, Pandu Poluan wrote:
> > > Strange...

> > > Do you use mdev to handle hotplugs, btw?

> > You mean, like sticking in a USB stick, or turning my printer on? Yes, I
> > do.

> No, I mean, did you do :

> echo /bin/mdev > /proc/sys/kernel/hotplug

No I haven't. I don't understand at all what this is about. Any chance
of a quick summary?

> (ensure beforehand that /bin/mdev is a symlink to /bin/busybox)

my /sbin/mdev is an indirect symlink to /bin/busybox as follows:
^

/sbin/mdev -> /bin/bb -> busybox

Presumably this would be OK.

> Rgds,

--
Alan Mackenzie (Nuremberg, Germany).

pandu at poluan

Mar 21, 2012, 8:38 AM

Post #11 of 11 (517 views)
Permalink

Re: mdev: sound is only working some of the time. [In reply to]

On Mar 21, 2012 10:04 PM, "Alan Mackenzie" <acm [at] muc> wrote:
>
> Hello again,
>
> On Wed, Mar 21, 2012 at 08:12:40PM +0700, Pandu Poluan wrote:
> > On Mar 21, 2012 8:07 PM, "Alan Mackenzie" <acm [at] muc> wrote:
>
> > > On Wed, Mar 21, 2012 at 07:49:02PM +0700, Pandu Poluan wrote:
> > > > Strange...
>
> > > > Do you use mdev to handle hotplugs, btw?
>
> > > You mean, like sticking in a USB stick, or turning my printer on?
Yes, I
> > > do.
>
>
> > No, I mean, did you do :
>
> > echo /bin/mdev > /proc/sys/kernel/hotplug
>
> No I haven't. I don't understand at all what this is about. Any chance
> of a quick summary?
>

According to the busybox documentation, /proc/sys/kernel/hotplug contains
the path to a program that will be invoked on hotplug events (hotplug here
means the creation of a new device node under /dev, not necessarily
actually plugging something onto the box).

Doing the above 'echo' will result in kernel invoking mdev when a hotplug
event fires; mdev will then act upon the newly-created device node
according to the 'recipe' in /etc/mdev.conf, e.g., chown-ing the node,
renaming/moving the node, making a symlink, or even triggering a script.

The above line should go right after the 'mdev -s' line in linuxrc.

> > (ensure beforehand that /bin/mdev is a symlink to /bin/busybox)
>
> my /sbin/mdev is an indirect symlink to /bin/busybox as follows:
> ^
>
> /sbin/mdev -> /bin/bb -> busybox
>
> Presumably this would be OK.
>

I think so...

Rgds,

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