linux-kernel - Re: [PATCH 1/3] dmaengine: add new dma API for max_segment

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Date:	Sun, 5 Jun 2011 10:30:20 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	shawn.guo@...escale.com
Cc:	vinod.koul@...el.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, dan.j.williams@...el.com,
	patches@...aro.org
Subject: Re: [PATCH 1/3] dmaengine: add new dma API for max_segment_number

On Wed, 1 Jun 2011 10:33:57 +0800
Shawn Guo <shawn.guo@...escale.com> wrote:

> On Thu, May 26, 2011 at 02:31:31PM +0800, Shawn Guo wrote:
> > Like dma_set(get)_max_seg_size for max_segment_size, the patch adds
> > max_segment_number into device_dma_parameters and creates the
> > corresponding dmaengine API dma_set(get)_max_seg_number for it.
> > 
> > Signed-off-by: Shawn Guo <shawn.guo@...aro.org>
> > ---
> >  include/linux/device.h      |    1 +
> >  include/linux/dma-mapping.h |   15 +++++++++++++++
> >  2 files changed, 16 insertions(+), 0 deletions(-)

include/linux/dma-mapping.h is for DMA mapping API (please see
Documentation/DMA-API*.txt).

What does dma_set(get)_max_seg_size do? And it's related with DMA
mapping API?


> > 
> > diff --git a/include/linux/device.h b/include/linux/device.h
> > index c66111a..44cb2528 100644
> > --- a/include/linux/device.h
> > +++ b/include/linux/device.h
> > @@ -487,6 +487,7 @@ struct device_dma_parameters {
> >  	 * sg limitations.
> >  	 */
> >  	unsigned int max_segment_size;
> > +	unsigned int max_segment_number;
> >  	unsigned long segment_boundary_mask;
> >  };
> >  
> > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> > index ba8319a..fd314f4 100644
> > --- a/include/linux/dma-mapping.h
> > +++ b/include/linux/dma-mapping.h
> > @@ -131,6 +131,21 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev,
> >  		return -EIO;
> >  }
> >  
> > +static inline unsigned int dma_get_max_seg_number(struct device *dev)
> > +{
> > +	return dev->dma_parms ? dev->dma_parms->max_segment_number : 1;
> > +}
> > +
> > +static inline unsigned int dma_set_max_seg_number(struct device *dev,
> > +						  unsigned int number)
> > +{
> > +	if (dev->dma_parms) {
> > +		dev->dma_parms->max_segment_number = number;
> > +		return 0;
> > +	} else
> > +		return -EIO;
> > +}
> > +
> >  static inline unsigned long dma_get_seg_boundary(struct device *dev)
> >  {
> >  	return dev->dma_parms ?
> > -- 
> > 1.7.4.1
> 
> --
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