[PATCH 11/31] dma: add channel request API that supports deferred probe

[Russell King - ARM Linux]

On Mon, Nov 25, 2013 at 09:45:18AM -0800, Dan Williams wrote:
> Regardless of whether the driver was dma_request_channel as a
> fallback, it will currently use NULL to indicate an allocation
> failure.

At the moment, dma_request_slave_channel()'s return values are valid
pointer or NULL.  I'd suggest as that's how it's been established,
that function is left alone - changing the return values in this kind
of invisible way is Really Bad(tm) because you can't check that it's
right in any future users - unless you're prepared to review every
single new user of this function for the next few years or more.

Instead, leaving it as is and introducing a new function name with
the different return error method is the right way to do this.