[PATCH][RFC] usbatm.[ch]: cleanup and OAM F5 loopback

Roman Kagan rkagan at mail.ru
Fri Mar 11 15:41:35 EST 2005

On Fri, Mar 11, 2005 at 08:54:14PM +0100, Marco d'Itri wrote:
> On Mar 11, Roman Kagan <rkagan at mail.ru> wrote:
> > In addition, I've put in some code to reply to OAM F5 Loopback cells
> > without passing them to the ATM layer (F4 should be easy too).
> Why? This *should* be handled by the ATM layer...

Maybe it eventually should, but it's going to need massive changes to
the way things work now.  At the moment the data goes to / from ATM
layer in the form of cooked AAL5 skbs, and adding OAM doesn't fit easily
into this model.  The patch living in the linux-atm tree is rather heavy
and adds a whole lot of ioctls and the like; in addition it requires a
userspace daemon to keep running on the same VC, which IMHO is a bit too

OTOH OAM loopback is as simple as taking the incoming cell, check if it
has the same VPI and VCI (for F5), check crc10, change 1 (one!) bit in
it, recalculate the crc10 and send it back.  Doesn't seem to be worth
letting it go outside the driver.


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