Finding out about drivers at runtime

Once you have a running Linux system, it is useful to know which device drivers are loaded and what state they are in. You can find out a lot by reading the files in /proc and /sys.

First of all, you can list the character and block device drivers currently loaded and active by reading /proc/devices:

# cat /proc/devices
Character devices:
  1 mem 
  2 pty 
  3 ttyp 
  4 /dev/vc/0 
  4 tty 
  4 ttyS 
  5 /dev/tty 
  5 /dev/console 
  5 /dev/ptmx 
  7 vcs 
 10 misc 
 13 input 
 29 fb 
 81 video4linux 
 89 i2c 
 90 mtd 
116 alsa 
128 ptm 
136 pts 
153 spi 
180 usb 
189 usb_device 
204 ttySC 
204 ttyAMA 
207 ttymxc 
226 drm 
239 ttyLP 
240 ttyTHS 
241 ttySiRF 
242 ttyPS 
243 ttyWMT 
244 ttyAS 
245 ttyO 
246 ttyMSM 
247 ttyAML 
248 bsg 
249 iio 
250 watchdog 
251 ptp 
252 pps 
253 media 
254 rtc 

Block devices:
259 blkext 
  7 loop 
  8 sd 
 11 sr 
 31 mtdblock 
 65 sd 
 66 sd 
 67 sd 
 68 sd 
 69...