Re: [PATCH 5/7 v2] dma: sh: use an integer slave ID to improve APIcompatibility

From: Vinod Koul
Date: Mon Jul 16 2012 - 05:38:26 EST

On Mon, 2012-07-16 at 10:47 +0200, Guennadi Liakhovetski wrote:
> > I want to know what does ccr and mid_rid mean to dmac here?
> CHCR contains a few fields, some enable various interrupt sources, some
> specify repeat- and renew-modes, others yet specify transfer size, source
> and destination address-modes (incrementing, constant, decrementing),
> others yet select a DMA client category (slave / memcpy / ...), and a
> transfer flag. Some of these fields could be calculated, others are
> pre-defined for various slaves, the exact layout of those fields can also
> vary between SoCs.
I do not understand how clients would provide these values.
For pre-defined values, they should be dmac property why should client
like spi or mmc have clue about it?

For others like you mentioned, i guess they could be easily calculated,

> MID_RID is actually a slave-selector, it contains a magic value, that
> cannot be calculated.
and again, how does client know this?


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