linux-kernel - Re: [PATCHv4] DMAEngine: Define interleaved transfer request api

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Date:	Mon, 10 Oct 2011 14:48:16 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Jassi Brar <jaswinder.singh@...aro.org>
Cc:	"Williams, Dan J" <dan.j.williams@...el.com>,
	Russell King <rmk@....linux.org.uk>,
	Barry Song <21cnbao@...il.com>, linux-kernel@...r.kernel.org,
	DL-SHA-WorkGroupLinux <workgroup.linux@....com>,
	Dave Jiang <dave.jiang@...el.com>
Subject: Re: [PATCHv4] DMAEngine: Define interleaved transfer request api

On Mon, 2011-10-10 at 14:46 +0530, Jassi Brar wrote:
> On 10 October 2011 12:23, Vinod Koul <vinod.koul@...el.com> wrote:
> >
> > +struct dmaxfer_memcpy_template {
> > +       dma_addr_t src_start;
> > +       dma_addr_t dst_start;
> > +       bool src_inc;
> > +       bool dst_inc;
> > +       bool src_sgl;
> > +       bool dst_sgl;
> > +       size_t numf;
> > +       size_t frame_size;
> > +       struct data_chunk sgl[0];
> > +};
> > +
> > +struct dmaxfer_slave_template {
> > +       dma_addr_t mem;
> > +       bool mem_inc;
> > +       size_t numf;
> > +       size_t frame_size;
> > +       struct data_chunk sgl[0];
> > +};
> >
> (1) Please tell how is dmaxfer_slave_template supposed to work on
>  bi-directional channels?
>  Keeping in mind, dma_slave_config.direction is marked to go away
>  in future.
I didn't use dma_slave_config.direction. There is direction field in
corresponding prepare function.

> 
> (2)
>   * slave_template.mem  <=>  memcpy_template.src_start
>   * slave_template.mem_inc  <=>  memcpy_template.src_inc
> 
>  So essentially
>   memcpy_template  :=  slave_template + src/dst_sgl + dst_start + dst_inc
> 
>  Even after this separation, there is nothing slave specific in
> dmaxfer_slave_template. The slave client still needs DMA_SLAVE_CONFIG
> to specify slave parameters of the transfer.
>  You only save a few bytes in a _copy_ of memcpy_template.
Yes DMA_SLAVE_CONFIG is always required, this attempt was not aimed to
remove that, but I would be interested in it :)

-- 
~Vinod

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