I have a USB microphone that works fine, up until I reboot my system. After that, it doesn't work at all until I unplug it and replug it.  Based on my (limited) understanding of the components involved, I think that ALSA isn't detecting the mic on boot (possibly because the appropriate module hasn't been loaded during the USB scan at system boot).  So, my question is,How can I either,Configure ALSA to look for USB devices when it gets initialized,Manually trigger ALSA to check for USB devices in a script I can    run at boot, orMake sure snd-usb-audio is loaded before the    initial scan for devices?I'm running a modified RHEL4 distribution, if that matters.  If there's more information you need, ask and I'll add it.From looking at /var/log/messages, here's what I see at boot with the mic plugged in:Mar 28 08:19:04 foobar kernel: usb 6-2: new full speed USB device using uhci_hcd and address 3Mar 28 08:19:04 foobar kernel: usb 6-2: New USB device found, idVendor=08bb, idProduct=2912Mar 28 08:19:04 foobar kernel: usb 6-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0Mar 28 08:19:04 foobar kernel: usb 6-2: Product: USB audio CODECMar 28 08:19:04 foobar kernel: usb 6-2: Manufacturer: Burr-Brown from TIMar 28 08:19:04 foobar kernel: usb 6-2: configuration #1 chosen from 1 choiceIf I later unplug the mic, I get a single line in messages:Mar 28 15:10:52 foobar kernel: usb 6-2: USB disconnect, address 3After boot, when I plug in the mic, I get the same output as above, but with one additional line:Mar 28 15:11:12 foobar kernel: usb 6-2: new full speed USB device using uhci_hcd and address 4Mar 28 15:11:12 foobar kernel: usb 6-2: New USB device found, idVendor=08bb, idProduct=2912Mar 28 15:11:12 foobar kernel: usb 6-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0Mar 28 15:11:12 foobar kernel: usb 6-2: Product: USB audio CODECMar 28 15:11:12 foobar kernel: usb 6-2: Manufacturer: Burr-Brown from TIMar 28 15:11:12 foobar kernel: usb 6-2: configuration #1 chosen from 1 choiceMar 28 15:11:12 foobar kernel: usbcore: registered new interface driver snd-usb-audio
Alsa not detecting USB microphone on system boot
usb;startup;alsa;usb audio
Well, I've got an answer to #2, found over at the Ubuntu stack exchange:sudo sh -c echo 0 > /sys/bus/usb/devices/<devId>/authorizedsudo sh -c echo 1 > /sys/bus/usb/devices/<devId>/authorizedwhere devId can be figured out (in my case, since I'll always know the exact expected product name) by inspecting /sys/bus/usb/devices/*/product