linux-kernel - Re: [PATCH 0/4 v4] dma: dma_{un}map_{single|sg}

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Date:	Thu, 13 Mar 2008 08:27:54 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	akepner@....com, Tony Luck <tony.luck@...el.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Jes Sorensen <jes@....com>, Roland Dreier <rdreier@...co.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	David Miller <davem@...emloft.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Grant Grundler <grundler@...isc-linux.org>,
	Michael Ellerman <michael@...erman.id.au>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4 v4] dma: dma_{un}map_{single|sg}_attrs() interface

On Thu, 13 Mar 2008 01:41:06 -0700 Andrew Morton wrote:

> > +#ifdef ARCH_USES_DMA_ATTRS
> 
> There is no precedent for ARCH_USES_*.
> 
> There is a little bit of precedent for ARCH_HAVE_*
> 
> There is lots of precendence for ARCH_HAS_*.
> 
> We don't like ARCH_HAS_* anyway ;) What can we do to get rid of this? 
> Ideally, make it available on all architectures at zero cost to those which
> don't need it.  If that is impractical (why?) then it is preferable to do
> this in Kconfig.

Sam has been pushing HAVE_* and even added that to
Documentation/kbuild/kconfig-language.txt.

> > +/*
> > + * dma_set_attr - set a specific attribute
> > + * may be called with a null attrs
> > + */

Use kernel-doc notation?

> > +static inline int dma_set_attr(struct dma_attrs *attrs, enum dma_attr attr)
> > +{
> > +	if (!attrs)
> > +		return 0;
> > +	if (attr < DMA_ATTR_MAX) {
> > +		attrs->flags |= (1 << attr);
> > +		return 0;
> > +	}
> > +	return -EINVAL;
> > +}
> 
> Is there any non-buggy reason why code would pass an out-of-range attribute
> into this function?  If not, BUG_ON() would be appropriate treatment.
> 
> This function might already be too large to inline, and a BUG_ON() might
> make it larger.
> 
> > +/*
> > + * dma_get_attr - check for a specific attribute
> > + * may be called with a null attrs
> > + */

Ditto.

> > +static inline int dma_get_attr(struct dma_attrs *attrs, enum dma_attr attr)
> > +{
> > +	if (!attrs)
> > +		return 0;
> > +	if (attr < DMA_ATTR_MAX) {
> > +		int ret = attrs->flags & (1 << attr);
> > +		return !!ret;
> > +	}
> > +	return -EINVAL;
> > +}


---
~Randy
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