Re: [PATCH 4/4] USB: add urb->unlinked field

On Tue, 21 Aug 2007, Greg KH wrote:

> On Tue, Aug 21, 2007 at 04:40:24PM -0400, Alan Stern wrote:
> > On Tue, 21 Aug 2007, Greg KH wrote:
> > 
> > > On Tue, Aug 21, 2007 at 03:40:36PM -0400, Alan Stern wrote:
> > > > This patch (as970) adds a new urb->unlinked field, which is used to
> > > > store the status of unlinked URBs since we can't use urb->status for
> > > > that purpose any more.  To help simplify the HCDs, usbcore will check
> > > > urb->unlinked before calling the completion handler; if the value is
> > > > set it will automatically override the status reported by the HCD.
> > > 
> > > Hm, is this field now safe to be used by drivers to determine if the urb
> > > is still being handled by the host controllers also?
> > 
> > You mean is the urb->status conversion finished?  Not yet.  I've got 
> > more patches still to test and submit.  It's getting there...
> 
> No, I mean is this something that drivers can use to check if the urb is
> finished with the HCD, like they currently check for -EINPROGRESS today.

Oh.  No, it isn't.  In fact, urb->unlinked won't take on a nonzero
value unless the URB actually is unlinked, so checking it won't
accomplish anything in the usual case where the USB completes normally.

Of course, drivers could _try_ using it to check if the URB is 
finished.  If they do, it'll quickly become obvious that the technique 
won't work.  :-)

Alan Stern


-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems?  Stop.
Now Search log events and configuration files using AJAX and a browser.
Download your FREE copy of Splunk now >>  http://get.splunk.com/
_______________________________________________
[email protected]
To unsubscribe, use the last form field at:
https://lists.sourceforge.net/lists/listinfo/linux-usb-devel