Date: Fri, 15 Jan 2010 14:01:53 -0800
From: "Ira W. Snyder" <iws@ovro.caltech.edu>
To: Stefani Seibold <stefani@seibold.net>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andi Kleen <andi@firstfloor.org>, Greg Kroah-Hartman <gregkh@suse.de>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>, Theodore Tso <tytso@mit.edu>
Subject: Re: [PATCH] enhanced reimplemented of the kfifo API
Message-ID: <20100115220153.GE10591@ovro.caltech.edu>
References: <1263546418.9732.11.camel@wall-e>
 <20100115192029.GC10591@ovro.caltech.edu>
 <1263591001.7531.1.camel@wall-e>
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On Fri, Jan 15, 2010 at 10:30:01PM +0100, Stefani Seibold wrote:
> 
> > I'm glad to see this example, it really illustrates how to use the new
> > DMA functionality of the kfifo API.
> > 
> > Is there any reason why a very large scatterlist could not be used? I
> > have a driver that uses a large scatterlist (~4000 entries, allocated as
> > a struct sg_table). I implemented my own copy_from_user() functionality
> > into this scatterlist, but I'd love to use the kfifo DMA API instead.
> > After filling the scatterlist, I use the usual DMA API's to transfer it
> > to my device.
> > 
> 
> No, but the API will only return max. two entries.
> 

Ah, I see. __kfifo_alloc() uses kmalloc() internally. The kfifo API will
not work for my purposes then, since I want to allocate a 16MB chunk of
memory, and I'm very uncomfortable doing that with kmalloc(). I'll stick
with my custom scatterlist code, which uses alloc_page() to fill in the
scatterlist with order-0 allocations.

Another nitpick in the code: I've noticed that you use sgl++ in the
setup_sgl() function. That should become "sgl = sg_next(sgl);" so that
this code can work with an struct sg_table as well.

Thanks,
Ira
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