[PATCH V3 1/2] of: Add generic device tree DMA helpers
Stephen Warren
swarren at wwwdotorg.org
Tue Jul 24 12:04:53 EDT 2012
On 07/24/2012 01:19 AM, Arnd Bergmann wrote:
> On Monday 23 July 2012, Stephen Warren wrote:
>>> 3. A device with three channels, one of which has two alternatives:
>>
>> s/three/four/ s/one of which/both of which/
>>
>> This binding doc seems reasonable to me.
>
> I asked a linguist about it who said that you can't have "both" together
> with "four". She also mentioned that my text is rather confusing, so maybe
> you also got it wrong. I'll try adding some explanation:
Oops, I guess I meant s/three/two/ :-)
It seems that given there are two values for dma-names, there really are
two channels; it's just that one channel is bi-directional, and the
second has two alternatives.
Still, I guess you could also view this as three separate channels
instead. In which case, the text below makes sense.
> 3. A device with three channels, one of which has two alternatives:
>
> dmas = <&dma0 1 4 /* first channel, data read */
> &dma0 2 6 /* second channel, data write */
> &dma1 1 0 /* third channel, error read */
> &dma2 1 0>; /* third channel, ernative error read */
> dma-names = "data", "data", "error", "error";
>
> The first two channels are identified by having a unique direction
> flag in combination with the "data" string. For the third channel,
> there are two dma specifiers with identical flags (1) and strings
> ("error"), so only one specifier may be used at a time.
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