Re: Change to ed_halted in ohci-q.c

On Wed, 15 Aug 2007, David Brownell wrote:

> On Monday 13 August 2007, Alan Stern wrote:
> > The idea is that when an URB gets an error, there's no need to put all 
> > the TDs after the one that failed through the done list.  They can be 
> > removed right away, and then the URB can be given back as soon as the 
> > failed TD is reached.
> 
> I'm not sure I see the point of this change though.  Was
> there some problem with how it worked before?  It'd be
> rare to have more than two TDs per URB in any case.

The point of this change is to pave the way for removing urb->status.  
Without that field available to cache an error code, it's easiest to
have HCDs return an URB as soon as an error is detected.  (The
exceptions are Iso URBs, obviously, and -EREMOTEIO in control URBs.  
They each will get special treatment.)

For ohci-hcd this means giving back an URB as soon as a bad TD is
encountered, without trying to do anything for all the remaining TDs.  
I don't see any point in adding them to the done list if later on the
driver will just have to take them back off while making a special
effort to ignore them.

> I don't recall exactly how that code ended up that way,
> but I expect the intent was to have a single "known to
> work" path through which TDs get reclaimed.

As long as there's nothing evidently wrong with the change, I'll be 
happy.  :-)

Alan Stern


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