Re: Can't Unload ALSA Driver Without Disconnecting the Device

[Takashi Iwai <tiwai@suse.de>]

At Fri, 12 Jun 2015 02:57:27 -0400,
Azizul Hakim wrote:
> 
> I see. So in this scenario what'll be the way to unload the driver
> successfully? Is there a way to stop the mixer interface?

Kill pulseaudio properly.  It'll auto respawn itself usually, so for
killing PA, you'd have to change the PA configuration.


Takashi

> 
> On Fri, Jun 12, 2015 at 2:55 AM, Takashi Iwai <tiwai@suse.de> wrote:
> 
> > 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@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
> > > >