Re: [PATCHv4] DMAEngine: Define interleaved transfer request api

[Vinod Koul]

On Mon, 2011-10-10 at 15:23 +0530, Jassi Brar wrote:
> On 10 October 2011 14:48, Vinod Koul <vinod.koul@xxxxxxxxx> wrote:
> > On Mon, 2011-10-10 at 14:46 +0530, Jassi Brar wrote:
> >> On 10 October 2011 12:23, Vinod Koul <vinod.koul@xxxxxxxxx> 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.
> >
> ok but why not reduce 1 argument from api and embed that as
> the transfer's property in dmaxfer_slave_template, as I did ?
I am not religious about it, doesn't matter either way :)
> 
> >>
> >> (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 :)
> >
> Sorry then I don't see this "ambiguity"(if there really is any) removal worth
> adding an extra prepare when we already have 10 of them.
For slave we have only two, and we can easily merge cyclic by adding a
flag or something, I planning to do that for next merge cycle.

IMO having one more for interleaved-slave should be okay.

But I am fine if we find a common ground and merge the two where dmac
can cleanly identify direction and mode it is operating.

-- 
~Vinod

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