Re: [PATCH] dmaengine: add dma_ctrl_cmd to pass buffer stride configuration
From: Linus Walleij
Date: Tue Jul 12 2011 - 06:03:28 EST
On Tue, Jul 12, 2011 at 6:17 AM, Jassi Brar <jassisinghbrar@xxxxxxxxx> wrote:
> 1) Striding, in one form or other, is supported by other DMACs as well.
> The number will only increase in future.
> Are we to add <VENDOR>_DMA_STRIDE_CONFIG for each case ?
If we are sure about this and striding will work in a similar way on all
then let's have the enum named DMA_STRIDE_CONFIG and move the
passed-in struct to <linux/dmaengine.h) then?
Would that be:
struct dma_stride_config {
u32 read_bytes;
u32 skip_bytes;
};
Or something more complex?
> 2) As Dan noted, client drivers are going to have ifdef hackery in
> order to be common
> to other SoCs.
Don't think so, why? This is a runtime config entirely, and I just illustrated
in mail to Dan how that can be handled by falling back to a sglist I believe?
We can *maybe* even put the fallback code into dmaengine, so that an
emulated sglist in place for the DMAengine is done automatically of the
DMA controller does not support striding.
> 3) TI may not have just one DMAC IP used in all the SoCs. So if you want
> vendor specific defines anyway, please atleast also add DMAC version to it.
> Something like
>> DMA_SLAVE_CONFIG,
>> FSLDMA_EXTERNAL_START,
>> + TI_DMA_v1_STRIDE_CONFIG,
Yep unless we make it generic DMA_STRIDE_CONFIG simply, this makes
a lot of sense.
Linus Walleij
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