[alsa-devel] Can't Unload ALSA Driver Without Disconnecting the Device

[Takashi Iwai]

At Fri, 12 Jun 2015 02:51:03 -0400,
Azizul Hakim wrote:
> 
> I tried that command. The output is as below:
> 
>                                     USER        PID ACCESS COMMAND
> /dev/snd/controlC0:  mhaki005   2043 F.... pulseaudio
> /dev/snd/controlC1:  mhaki005   2043 F.... pulseaudio
> /dev/snd/pcmC0D0c:   mhaki005   2043 F...m pulseaudio
> 
> 
> I think pcmC0D0c stands for "Capture" device. My device is a playback
> device. So I don't think it is being used by anyone.

/dev/snd/controlC1 is being used.  It's the mixer interface.


Takashi

> 
> 
> On Fri, Jun 12, 2015 at 2:41 AM, Takashi Iwai <tiwai at suse.de> wrote:
> 
> > At Fri, 12 Jun 2015 02:28:16 -0400,
> > Azizul Hakim wrote:
> > >
> > > Hi,
> > >
> > > I've been developing a sound card driver for a USB device using ALSA. My
> > > driver is almost working but I've got one small issue. If I try to unload
> > > the driver module using "rmmod" command  when the device is still
> > connected
> > > to the USB port, it says "Module is in use" even though I'm not playing
> > any
> > > sound files or anything.
> > >
> > >
> > > If I try to execute the "lsmod" command I see that it is saying the usage
> > > count of my driver to be 1, but it doesn't say anything about who is
> > using
> > > it. Once I disconnect the device from the USB port, I can easily unload
> > the
> > > module.
> > >
> > >
> > > So it seems to me it won't be possible to unload a sound card driver if
> > the
> > > card is attached in the computer. Is my assumption correct? If not, what
> > > might be some key points to solve the issue?
> >
> > Check "fuser -v /dev/snd/*" as root.  Something (e.g. a mixer
> > application or sound backend) must be accessing the device.
> >
> >
> > Takashi
> >
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>