Subject: Re: e100 "Ferguson" release

From: David Brownell <[email-masked]>
Date: Sun, 03 Aug 2003 21:08:26 -0700

David S. Miller wrote:
> On Sun, 03 Aug 2003 20:45:01 -0700
> David Brownell <[email-masked]> wrote:
> 
> 
>>What can't be pre-allocated in a reliable way is the resources
>>used by the host controller drivers, specifically the transfer
>>descriptors.  EHCI and OHCI usually need one per URB, unless
>>MTU is over 4 KB.  UHCI normally needs quite a few.
> 
> 
> Ok, that's interesting.

All TDs get allocated in usb_submit_urb(), which is the first
time the "real" core of USB connects an urb with an I/O queue.
That's host-side, not device-side.

> Is there a callback that tells the USB driver that some host
> controller "resources" have become available?  I mean, these host
> controllers either have to queue requests when out of resources or
> provide a callback so that the drivers can resubmit.

No such callback.  If no resources, they fail -ENOMEM and the
caller must recover.  Which is why hard_start_xmit() needs to
do something.

- Dave