[alsa-devel] aplay lists both Playback and Capture devices

[Mark Brown]

On Sat, Jun 01, 2013 at 06:36:49PM -0300, Fabio Estevam wrote:
> On Sat, Jun 1, 2013 at 6:05 PM, Mark Brown <broonie at kernel.org> wrote:

> > If it's not got any playback or capture capabilities.

> On mx28evk there are two DAIs connected to a single sgtl5000:

> - One corresponds to the serial audio interface 0 (SAIF0) and it is
> playback only

> - The other corresponds to the serial audio interface 1 (SAIF1) and it
> is capture only.

These are not DAIs, they are DAI links.  The capabilities of the links
should be being worked out by examining

> Should I create and pass device tree bindings like "playback-only" and
> "capture-only", so that we can avoid having both playback and capture
> capabilities for SAIF0 and SAIF1?

No, it's not sensible to require users to set DT properties for basic
features of the harwdare.  If for some reason the interface could be
bidirectional but the board design breaks that for some reason then it
may make sense but otherwise the kernel ought to be able to work this
out based on the fact that one or both ends of the link can only do one
direction.

> Or is there already a mechanism in place that I can use to configure a
> DAI as unidirectional?

How is the kernel currently managing to get properties for playback?
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