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Message-ID: <20080201030751.GB28899@sgi.com>
Date: Thu, 31 Jan 2008 19:07:51 -0800
From: akepner@....com
To: Grant Grundler <grundler@...isc-linux.org>
Cc: Tony Luck <tony.luck@...el.com>,
Jesse Barnes <jbarnes@...tuousgeek.org>,
Jes Sorensen <jes@....com>,
Randy Dunlap <randy.dunlap@...cle.com>,
Roland Dreier <rdreier@...co.com>,
James Bottomley <James.Bottomley@...senPartnership.com>,
David Miller <davem@...emloft.net>,
Muli Ben-Yehuda <muli@...ibm.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] dma: document dma_{un}map_{single|sg}_attrs() interface
On Thu, Jan 31, 2008 at 03:38:48PM -0700, Grant Grundler wrote:
Thanks for looking through this.
I'll send an updated patchset that addresses your comments
as soon as I can - probably around Monday.
> ...
> > +struct dma_attrs encapsulates a set of "dma attributes". For the
> > +definition of struct dma_attrs see linux/dma-attrs.h.
>
> Because all architectures will share the set of attrs definitions,
> would it be reasonable to document the intent of each attr?
>
> Two reasons for doing this:
> 1) people reading the driver code should understand WHY the dma attr was added.
> 2) other arch maintainers need to know in order to implement the same attr
> for their shiny new toys.
>
>
> > +The interpretation of dma attributes is architecture-specific.
>
> This statement is really important....but:
> Could we add a reference to arch documentation for each attr?
>
> ie something public (doesn't have to be in linux source tree)
> which explains the subtlies of how that DMA attr actually works.
>
> Having worked on HP chipsets for 10+ years, I know releasing
> original HW docs is often not possible. I'm not asking for the
> impossible. Please don't flame me for that. But if the company
> is willing to publish the existance of a feature, a paragraph or
> two would be good marketing too. Maybe just include comments in
> the arch/ code that implements the feature and reference those
> comments in DMA-API.txt.
> ....
OK, I can certainly add an explanation of the attribute that
I'm worried about.
I think there's a reference to this behavior in our driver
porting guide - I can add a pointer to that, too.
This might also address your point above about documenting
each attribute - let me know once the next patch is out.
--
Arthur
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