On Tuesday 24 July 2012, Stephen Warren wrote:

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.

quoted

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";

A bidirectional channel would have only one request line, not two,
and we would write that as

	dmas = <&dma0 3 4>; /* one channel on dmarq 4, read-write */


	Arnd