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Date:      Fri, 5 Jul 2002 09:45:01 -0700 (PDT)
From:      John Polstra <jdp@polstra.com>
To:        net@freebsd.org
Subject:   Re: virtually contig jumbo mbufs (was Re: new zero copy sockets snapshot)
Message-ID:  <200207051645.g65Gj1lM003467@vashon.polstra.com>
In-Reply-To: <15653.35606.290023.621040@grasshopper.cs.duke.edu>
References:  <20020619090046.A2063@panzer.kdm.org> <20020705002056.A5365@unixdaemons.com> <20020704231321.A42134@panzer.kdm.org> <15653.35606.290023.621040@grasshopper.cs.duke.edu>

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In article <15653.35606.290023.621040@grasshopper.cs.duke.edu>,
Andrew Gallatin  <gallatin@cs.duke.edu> wrote:
> Kenneth D. Merry writes:
>  > I suppose it would be good to see what NIC drivers in the tree can receive
>  > into or send from multiple chunks of data, and what their requirements are.
>  > (how many scatter/gather segments they can handle, what is the maximum MTU,
>  > etc.)
> 
> If you're just looking at the code, then this would be hard.  All the
> current drivers (with the exception of em) are coded to take one
> physically contiguous private buffer.  I'm pretty sure that most of
> them are capable of doing scatter DMA, but I don't have the
> programming docs.

The BCM570x chips (bge driver) definitely need a single physically
contiguous buffer for each received packet.

John
-- 
  John Polstra
  John D. Polstra & Co., Inc.                        Seattle, Washington USA
  "Disappointment is a good sign of basic intelligence."  -- Chögyam Trungpa


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