Re: Disabling USB

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Tue, 4 Dec 2007, Przemyslaw Lopaciuk wrote:

> 
> Thank you for your reply... I think that you misunderstood my 
> question... I want to write function let's say... disableUSB() that 
> would disable USB when invoked...
> As I understand you can pass kernel command line parameters while 
> booting. Can you do that also when the kernel is running?
> If yes than how?

You can unbind the host controller drivers from the controller devices.  
This can be done using sysfs.  You would have to iterate through these 
directories:

	/sys/bus/usb/devices/usb*/../driver

In each of those directories, iterate through all the symbolic links 
(you can omit the link named "module" if it's present) and write the 
name of the link to the "unbind" file.

For example on my system:

$ cd /sys/bus/usb/devices/usb1/../driver/
$ ls -l 
total 0
lrwxrwxrwx 1 root root    0 Dec  4 10:30 0000:00:1d.0 -> 
../../../../devices/pci0000:00/0000:00:1d.0/
lrwxrwxrwx 1 root root    0 Dec  4 10:30 0000:00:1d.1 -> 
../../../../devices/pci0000:00/0000:00:1d.1/
lrwxrwxrwx 1 root root    0 Dec  4 10:30 0000:00:1d.2 -> 
../../../../devices/pci0000:00/0000:00:1d.2/
lrwxrwxrwx 1 root root    0 Dec  4 10:30 0000:01:01.0 -> 
../../../../devices/pci0000:00/0000:00:1e.0/0000:01:01.0/
lrwxrwxrwx 1 root root    0 Dec  4 10:30 0000:01:01.1 -> 
../../../../devices/pci0000:00/0000:00:1e.0/0000:01:01.1/
--w------- 1 root root 4096 Dec  4 10:30 bind
lrwxrwxrwx 1 root root    0 Dec  4 10:30 module -> 
../../../../module/uhci_hcd/
--w------- 1 root root 4096 Dec  4 10:30 new_id
--w------- 1 root root 4096 Dec  4 10:30 unbind

So I would then have to do the equivalent of:

	echo -n 0000:00:1d.0 >unbind
	echo -n 0000:00:1d.1 >unbind
	echo -n 0000:00:1d.2 >unbind
	echo -n 0000:01:01.0 >unbind
	echo -n 0000:01:01.1 >unbind

Then do the same thing for /sys/bus/usb/devices/usb2/../driver, and so 
on, until no more of these directories are left.

Alan Stern


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