Re: [PATCH v2 1/2] dmaengine: Add support for per xfer specific privatedata& box dma

[Ravi Kumar V]

On 1/17/2012 7:23 PM, Vinod Koul wrote:
> On Fri, 2012-01-06 at 18:17 +0530, Ravi Kumar V wrote:
> > diff --git a/include/asm-generic/scatterlist.h b/include/asm-generic/scatterlist.h
> > index 5de0735..e66dfcb 100644
> > --- a/include/asm-generic/scatterlist.h
> > +++ b/include/asm-generic/scatterlist.h
> > @@ -14,6 +14,7 @@ struct scatterlist {
> >   #ifdef CONFIG_NEED_SG_DMA_LENGTH
> >   	unsigned int	dma_length;
> >   #endif
> > +	unsigned long	private_data;
> what do you plan to pass here. Please keep in mind this is a generic
> scatterlist structure, and modifying it for your purposes doesn't seem
> to be a great one!
> Also why can't you pass this as addition argument in your new "BOX API"?
We are using DMA-Engine framework for both SG mode and BOX mode of our HW.
For SG mode we are using device_prep_dma_sg API but the problem we are 
facing is we need to pass command configuration parameter along with 
each descriptor to our HW, we did not find any suitable API/structure in 
framework to support this.
So thought of adding new element in struct scatterlist.
please can you suggest a way to pass private parameter with
every descriptor.
> >   };
> >
> >   /*
> > +
> > +struct dma_box_list {
> > +	dma_addr_t dma_row_address;
> > +	unsigned int dma_row_len;
> > +	unsigned int dma_row_num;
> > +	unsigned int dma_row_offset;
> > +	unsigned long private_data;
> > +};
> again a private data here?
> is this some kind of interleaved pattern?
Yes this interleaved pattern.
> > +
> >   /**
> >    * struct dma_device - info on the entity supplying DMA services
> >    * @chancnt: how many DMA channels are supported
> > @@ -497,6 +507,11 @@ struct dma_device {
> >   	struct dma_async_tx_descriptor *(*device_prep_dma_cyclic)(
> >   		struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
> >   		size_t period_len, enum dma_data_direction direction);
> > +	struct dma_async_tx_descriptor *(*device_prep_dma_box)(
> > +		struct dma_chan *chan, struct dma_box_list *dst_box,
> > +		struct dma_box_list *src_box, unsigned int num_list,
> > +		unsigned long flags);
> still not clean what kind of transfer do you want to do here
We are doing interleaved pattern of data transfer between source and 
destination boxs, num_list is number of box mode commands
Please can you refer patch 0/2 I have replied explaining about box mode 
transfer clearly.
> > +
> >   	int (*device_control)(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> >   		unsigned long arg);


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