How to find SCSI device to USB device association.

[greg@kroah.com (Greg KH)]

On Mon, May 09, 2011 at 02:07:57PM -0700, StephanT wrote:
> 
> 
> > Why would you want  such a mapping?  It's not stable, changes every time,
> > and means  nothing.
> 
> Well, because it is a customer/marketing request. And they have _always_
> the last word :)

Even if it is an incorrect one, {sigh}.

> The system I'm working now is an embedded box having four USB ports. Each
> port is labeled on the box USB1, USB2,... and the user expects to find the 
> files 
> on the stick plugged in USB1 on /media/usb1 folder. You can see my problem.

Yes, that's not a nice one.

The _only_ way you are going to resolve this is to look at the USB path
id of the device.  It will show you which port the device is plugged
into, and you are going to have to go off of that.

But watch out, you need to ignore USB bus and device ordering issues, as
they will change randomly.

> It happens the USB port labeled USB1 on the box has the port number 4. The 
> USB2 is the #3 and so on. The solution I was thinking of is to add a rule to the
> UDEV USB section invoking a script which will create a logical link 
> "/media/usbx"
> depending of the USB port#  attached to the newly created "sda_". This link 
> is created every time the device is mounted and removed on umount.
> 
> Maybe you can suggest something simpler.

Look at /dev/disk/by-path/ the links are already set up for you there
that you can use.

good luck,

greg k-h