Re: [PATCHv4] DMAEngine: Define interleaved transfer request api
From: Jassi Brar
Date: Mon Oct 10 2011 - 05:53:49 EST
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 ?
>>
>> (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.
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