A while ago, I posted about TIOCMIWAIT not working with the PL2303
USB-serial adapter.

After a brief exchange with Greg, I tracked this to a missing wake-up
in the USB interrupt procedures. I got our systems staff to install
the enclosed very simple patch to our 2.6.12 kernels, and it all works
fine as expected. I guess this should also apply to the latest version
and go into the mainstream.

Apologies for the long delay in posting the result.

The routine being patched is pl2303_update_line_status

Signed-off-by: Julian Bradfield <jcb+luu@inf.ed.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>