/proc/bus/usb/devices

And, it’s default path if you are on kernel 2.6.31 and usbfs is mounted by Init. Now, Ubuntu 9.10 is using upstart instead of init. It was working fine in Ubuntu 9.04. So it brought me in big world of usbfs. From Scott’s post usbfs: deprecate and hide option for !embedded. usbfs was enabled #417748 and disabled#488274 in Karmic Koala Released and Proposed version.

Ok, Ping back to original query, Ubuntu 9.10 is mounting debugfs instead of usbfs, regardless of  usbfs in enabled / disabled in Kernel. So you will fine usb/devices file under /sys/kernel/debug directory, check below output:

person@CANONICAL-DESK:/proc/bus$ mount
/dev/sda6 on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)

….

person@CANONICAL-DESK:/proc/bus$person@CANONICAL-DESK:/proc/bus$

person@CANONICAL-DESK:/proc/bus$ uname -a
Linux CANONICAL-DESK 2.6.31-20-generic #57-Ubuntu SMP Mon Feb 8 09:05:19 UTC 2010 i686 GNU/Linux
person@CANONICAL-DESK:/proc/bus$ cat /sys/kernel/debug/usb/devices

…

T:  Bus=03 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#=  2 Spd=12  MxCh= 0
D:  Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=046d ProdID=0a12 Rev= 1.00
S:  Manufacturer=Logitech
S:  Product=Logitech Wireless Headset
C:* #Ifs= 4 Cfg#= 1 Atr=80 MxPwr=100mA
I:* If#= 0 Alt= 0 #EPs= 0 Cls=01(audio) Sub=01 Prot=00 Driver=snd-usb-audio
I:* If#= 1 Alt= 0 #EPs= 0 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
I:  If#= 1 Alt= 1 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
E:  Ad=01(O) Atr=09(Isoc) MxPS= 288 Ivl=1ms
I:* If#= 2 Alt= 0 #EPs= 0 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
I:  If#= 2 Alt= 1 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio
E:  Ad=82(I) Atr=05(Isoc) MxPS=  32 Ivl=1ms
I:* If#= 3 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=00 Prot=00 Driver=usbhid
E:  Ad=83(I) Atr=03(Int.) MxPS=   8 Ivl=10ms

…
person@CANONICAL-DESK:/proc/bus$

Currently i am testing this on Ubuntu 10.04 (Lucid Lynx) Alpha 3, and behavior is almost same. But it contains  new version of usbutils, which has new shell script called “usb-devices”. It will give you connected USB buses with machine, regardless of where your usb/devices file is! and output is almost same. check below output

hardik@hardik-desktop:~$ uname -a
Linux hardik-desktop 2.6.32-16-generic-pae #25-Ubuntu SMP Tue Mar 9 18:03:39 UTC 2010 i686 GNU/Linux
hardik@hardik-desktop:~$ usb-devices

…

T:  Bus=01 Lev=02 Prnt=02 Port=04 Cnt=01 Dev#=  3 Spd=12  MxCh= 0
D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=046d ProdID=c52e Rev=15.00
S:  Manufacturer=Logitech
S:  Product=USB Receiver
C:  #Ifs= 2 Cfg#= 1 Atr=a0 MxPwr=98mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=01 Driver=usbhid
I:  If#= 1 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=02 Driver=usbhid

…

This question  was asked by my  friend Mr.  Sunil and  it turns in to  blog . That’s it for now…