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

[Azizul Hakim]

Thanks. It was a great help :)

On Fri, Jun 12, 2015 at 3:01 AM, Takashi Iwai <tiwai at suse.de> wrote:

> 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 at 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 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
> > > > >
>