Hoje me surgiu a necessidade de descobrir qual era o dispositivo de entrada do meu microfone traseiro. O problema é que no meu caso existe mais de uma dezena de dispositivos de entrada no meu PC, como saber qual é o /dev/input/event(?) correto do meu microfone?

ls /dev/input
event0
event1
event10
event11
event12
event13
event14
event2
event3
event4
event5
event6
event7
event8
event9
mice
mouse0

Para uma lista detalhada podemos consultar o arquivo /proc/bus/input/devices:

cat /proc/bus/input/devices

I: Bus=0019 Vendor=0000 Product=0001 Version=0000
N: Name="Power Button"
P: Phys=PNP0C0C/button/input0
S: Sysfs=/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0C:00/input/input0
U: Uniq=
H: Handlers=kbd event0 
B: PROP=0
B: EV=3
B: KEY=10000000000000 0

I: Bus=0019 Vendor=0000 Product=0001 Version=0000
N: Name="Power Button"
P: Phys=LNXPWRBN/button/input0
S: Sysfs=/devices/LNXSYSTM:00/LNXPWRBN:00/input/input1
U: Uniq=
H: Handlers=kbd event1 
B: PROP=0
B: EV=3
B: KEY=10000000000000 0

I: Bus=0019 Vendor=0000 Product=0006 Version=0000
N: Name="Video Bus"
P: Phys=LNXVIDEO/video/input0
S: Sysfs=/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input2
U: Uniq=
H: Handlers=kbd event2 
B: PROP=0
B: EV=3
B: KEY=3e000b00000000 0 0 0

I: Bus=0003 Vendor=258a Product=0001 Version=0110
N: Name="SINO WEALTH USB KEYBOARD"
P: Phys=usb-0000:00:1a.0-1.3/input0
S: Sysfs=/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.3/1-1.3:1.0/0003:258A:0001.0001/input/input3
U: Uniq=
H: Handlers=sysrq kbd leds event3 
B: PROP=0
B: EV=120013
B: KEY=1000000000007 ff9f207ac14057ff febeffdfffefffff fffffffffffffffe
B: MSC=10
B: LED=7

I: Bus=0003 Vendor=258a Product=0001 Version=0110
N: Name="SINO WEALTH USB KEYBOARD System Control"
P: Phys=usb-0000:00:1a.0-1.3/input1
S: Sysfs=/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.3/1-1.3:1.1/0003:258A:0001.0002/input/input4
U: Uniq=
H: Handlers=kbd event4 
B: PROP=0
B: EV=13
B: KEY=c000 10000000000000 0
B: MSC=10

I: Bus=0003 Vendor=258a Product=0001 Version=0110
N: Name="SINO WEALTH USB KEYBOARD Consumer Control"
P: Phys=usb-0000:00:1a.0-1.3/input1
S: Sysfs=/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.3/1-1.3:1.1/0003:258A:0001.0002/input/input5
U: Uniq=
H: Handlers=kbd event5 
B: PROP=0
B: EV=13
B: KEY=2a000000000 0 0 1000002000000 3878d8011001 e000000000000 0
B: MSC=10

I: Bus=0003 Vendor=046d Product=c408 Version=0110
N: Name="Logitech USB Trackball"
P: Phys=usb-0000:00:1a.0-1.4/input0
S: Sysfs=/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.4/1-1.4:1.0/0003:046D:C408.0003/input/input6
U: Uniq=
H: Handlers=mouse0 event6 
B: PROP=0
B: EV=17
B: KEY=1f0000 0 0 0 0
B: REL=3
B: MSC=10

I: Bus=0010 Vendor=001f Product=0001 Version=0100
N: Name="PC Speaker"
P: Phys=isa0061/input0
S: Sysfs=/devices/platform/pcspkr/input/input7
U: Uniq=
H: Handlers=kbd event7 
B: PROP=0
B: EV=40001
B: SND=6

I: Bus=0000 Vendor=0000 Product=0000 Version=0000
N: Name="HDA Intel PCH Rear Mic"
P: Phys=ALSA
S: Sysfs=/devices/pci0000:00/0000:00:1b.0/sound/card0/input8
U: Uniq=
H: Handlers=event8 
B: PROP=0
B: EV=21
B: SW=10

I: Bus=0000 Vendor=0000 Product=0000 Version=0000
N: Name="HDA Intel PCH Line"
P: Phys=ALSA
S: Sysfs=/devices/pci0000:00/0000:00:1b.0/sound/card0/input9
U: Uniq=
H: Handlers=event9 
B: PROP=0
B: EV=21
B: SW=2000

I: Bus=0000 Vendor=0000 Product=0000 Version=0000
N: Name="HDA Intel PCH Headphone"
P: Phys=ALSA
S: Sysfs=/devices/pci0000:00/0000:00:1b.0/sound/card0/input10
U: Uniq=
H: Handlers=event10 
B: PROP=0
B: EV=21
B: SW=4

I: Bus=0000 Vendor=0000 Product=0000 Version=0000
N: Name="HDA Intel PCH HDMI/DP,pcm=3"
P: Phys=ALSA
S: Sysfs=/devices/pci0000:00/0000:00:1b.0/sound/card0/input11
U: Uniq=
H: Handlers=event11 
B: PROP=0
B: EV=21
B: SW=140

I: Bus=0000 Vendor=0000 Product=0000 Version=0000
N: Name="HDA Intel PCH HDMI/DP,pcm=7"
P: Phys=ALSA
S: Sysfs=/devices/pci0000:00/0000:00:1b.0/sound/card0/input12
U: Uniq=
H: Handlers=event12 
B: PROP=0
B: EV=21
B: SW=140

I: Bus=0000 Vendor=0000 Product=0000 Version=0000
N: Name="HDA Intel PCH HDMI/DP,pcm=8"
P: Phys=ALSA
S: Sysfs=/devices/pci0000:00/0000:00:1b.0/sound/card0/input13
U: Uniq=
H: Handlers=event13 
B: PROP=0
B: EV=21
B: SW=140

I: Bus=0003 Vendor=046d Product=0825 Version=0012
N: Name="UVC Camera (046d:0825)"
P: Phys=usb-0000:00:14.0-2/button
S: Sysfs=/devices/pci0000:00/0000:00:14.0/usb2/2-2/2-2:1.0/input/input14
U: Uniq=
H: Handlers=kbd event14 
B: PROP=0
B: EV=3
B: KEY=100000 0 0 0

Muita informação na tela não é verdade? O que nos importa na saída são as linhas "Name" e "Handlers", então vamos usar a combinação do comando grep para filtrá-las e o paste para colocá-las na mesma linha:

cat /proc/bus/input/devices | grep -P '^[NH]: ' | paste - -

N: Name="Power Button"	H: Handlers=kbd event0 
N: Name="Power Button"	H: Handlers=kbd event1 
N: Name="Video Bus"	H: Handlers=kbd event2 
N: Name="SINO WEALTH USB KEYBOARD"	H: Handlers=sysrq kbd leds event3 
N: Name="SINO WEALTH USB KEYBOARD System Control"	H: Handlers=kbd event4 
N: Name="SINO WEALTH USB KEYBOARD Consumer Control"	H: Handlers=kbd event5 
N: Name="Logitech USB Trackball"	H: Handlers=mouse0 event6 
N: Name="PC Speaker"	H: Handlers=kbd event7 
N: Name="HDA Intel PCH Rear Mic"	H: Handlers=event8 
N: Name="HDA Intel PCH Line"	H: Handlers=event9 
N: Name="HDA Intel PCH Headphone"	H: Handlers=event10 
N: Name="HDA Intel PCH HDMI/DP,pcm=3"	H: Handlers=event11 
N: Name="HDA Intel PCH HDMI/DP,pcm=7"	H: Handlers=event12 
N: Name="HDA Intel PCH HDMI/DP,pcm=8"	H: Handlers=event13 
N: Name="UVC Camera (046d:0825)"	H: Handlers=kbd event14 

Agora sim ficou fácil identificar os dispositivos de entrada! No meu caso o "Rear Mic" (microfone traseiro) está no "event8", ou seja, /dev/input/event8.