Signal when device is disconnected

["Phil Endecott" <phil_joqdm_endecott@chezphil.org>]

Dear Experts,

The proc/bus/usb API has an ioctl that can arrange for the application 
to receive a signal when the device is disconnected.  Is there anything 
similar for the SCSI generic (or other SCSI) APIs?

Assuming that there isn't, I think I need to either poll the device to 
see if it's still there, or listen on a netlink socket for a removal 
uevent, or I need to find the USB device corresponding to the sg device 
that I'm using and use its signal-on-removal ioctl.  In the latter 
case, is there a way to traverse from an sg device's /sys directory to 
the corresponding usb device's /sys directory?  /sys seems to be full 
of symlinks but I can't find the one that I need in this case.

Basically I have a fairly simple user-space driver for a USB SCSI 
device that uses the SCSI-generic API, and I want it to terminate 
tidily when the device is detached.

Many thanks for any advice.


Phil.

(Please Cc: me in any replies.)