Al Viro wrote:

BTW, snd_card_disconnect() doesn't do anything to existing mappings; smells like a bug, and there we do have ones with non-trivial ->mmap(). Could ALSA folks comment?

I don't know of any hotplug sound driver that maps memory from a device. All hotplug buses (PCIe, USB, FireWire) involve DMAing from/to main memory.

When a sound device is unplugged, sample transfers just stop, but the buffer itself stays as long as the device node is kept opened. (In the case of a capture device, that actually makes sense.)

Regards, Clemens