Subject: Re: [RFC][PATCH] TTY flip buffer SMP changes
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Theodore Ts'o" <tytso@mit.edu>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, Paul Fulghum <paulkf@microgate.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
In-Reply-To: <20041008150055.GA13870@thunk.org>
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Date: Sat, 09 Oct 2004 11:42:35 +1000
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On Sat, 2004-10-09 at 01:00, Theodore Ts'o wrote:

> You can have the driver hang on to the sk_buff for several interrupts
> until it decides to push the data to the line displine.  So even if
> the FIFO is small, we only have to allocate/deallocate the skbuff only
> but rarely, unless someone really needs low_latency --- which should
> be but rarely. 

That reminds me... a while ago, I toyed with the idea of having DMA
support in pmac_zilog. The case where it would work well is typically
for things that have a known sized frame. If that information was
provided down to the driver, I could setup the DMA descriptor for
that frame size & have it interrupt me when the frame is complete,
along with a timeout set to the estimated time for receiving such
a frame + X% (I was thinking +20%)

Ben.


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