Re: suspend/resume for usb serial devices

Hello all,

First off, a big thanks to Oliver for his help.

Attached is my first version of the changes needed for the Sierra 
Wireless driver to support suspend / resume.  It requires the patch 
Oliver created which supplies the infrastructure in the generic USB 
serial code.

The code works... in the sense that the system doesn't immediately crash 
or anything when plugging in a modem.  However, we have just begun the 
testing, so we don't know if suspend / resume is actually working properly.

Mostly we'd like to know if we're following the correct style, and if 
there's any obvious problems in the way we've added the suspend / resume 
support to the Sierra Wireless driver.

------------------------------------------------------

I'm confused slightly by the patch created by Oliver on March 20th 
concerning a race condition in the Sierra Wireless driver upon close.

   http://marc.info/?l=linux-usb-devel&m=117451402229177&w=4

In the patch I've attached, we've created a helper function to actually 
unlink all the URBs, but the commentary on Oliver's March 20th patch 
seems to indicate that this is not a good idea.  But I don't understand why.

------------------------------------------------------

There are two patches attached:

     generic_usb_susp_20070426.patch

This is Oliver's patch to add the infrastructure for suspend / resume 
for serial drivers in general.

     sierra_suspend_resume_v107.patch

This is a patch against the v1.0.6 version of the sierra.c in Linux 
kernel version 2.6.21.  Since the Sierra Wireless driver uses multiple 
URBs, it unlinks then all upon suspend.  And, obviously, submits them 
again on resume.

It also includes the patch Greg posted on the 21st which does some null 
pointer checking.

   http://marc.info/?l=linux-usb-devel&m=117451402229177&w=4

And it uses usb_unlink_urb() instead of stop_urb() as suggested by Oliver.

Please let me know what you think.

James Graves
Delta Mobile Software, Inc.

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