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

[Takashi Iwai]

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