[pulseaudio-discuss] Jack detection - from the other side

[Tanu Kaskinen]

On Mon, 2011-07-04 at 16:32 +0200, David Henningsson wrote:
> It's time to get a little momentum on the Jack detection again. I hope 
> to be able to work with it this week.
> 
> As you might know, my udev patch turned controversial [1] [2], so I 
> decided to attack the problem from another angle. Here's a preliminary 
> idea of how the API could look like from the "volume control UI" 
> perspective. As Tanuk originally suggested, every port now has an 
> "available" property which can be yes/no/unknown. Also imagine the same 
> thing implemented for sources as now being presented for sinks.

I would much prefer if patches would be sent with git send-email unless
they are perfect, because commenting is much easier with inline
patches...

Using copy-paste then:

> diff --git a/src/pulse/introspect.h b/src/pulse/introspect.h
> index 196d44d..6f62497 100644
> --- a/src/pulse/introspect.h
> +++ b/src/pulse/introspect.h
> @@ -193,6 +193,10 @@
>  
>  PA_C_DECL_BEGIN
>  
> +#define PA_PORT_AVAILABLE_UNKNOWN (0)   /**< This port does not support jack detection \since MERGE_OF_JACK_DETECTION */
> +#define PA_PORT_AVAILABLE_NO (1)        /**< This port is not available, likely because the jack is not plugged in. \since MERGE_OF_JACK_DETECTION */
> +#define PA_PORT_AVAILABLE_YES (2)       /**< This port is available, likely because the jack is plugged in. \since MERGE_OF_JACK_DETECTION */

Should these be in pulse/def.h? Glancing around quickly it looks like
there are no other constants defined in introspect.h. I'd also introduce
an enum type for these.

> +    int switch_on_avail;                /**< Boolean indicating that when "available" changes to PA_PORT_AVAILABLE_YES, streams should move to this sink. \since MERGE_OF_JACK_DETECTION */

Why is this needed? Automatic moving of streams on jack events is
policy, and thus it's something that the core shouldn't be involved in,
IMO.

> +/** Change the "switch_on_available" attribute of a port of a sink. \since MERGE_OF_JACK_DETECTION */
> +pa_operation* pa_context_set_sink_port_switch_on_avail_by_index(pa_context *c, uint32_t idx, const char*port, int switch_on_available, pa_context_success_cb_t cb, void *userdata);

Ah, this is what it was needed for. I still have my opinion - this
function doesn't belong to the core API. I think we should have a module
that implements the move-on-jack-insert policy and provides the client
API if that's needed.

> +int pa_sink_set_port_available(pa_sink *s, const char *name, int available);

I guess this is left without implementation on purpose?

The function is put under the callable-by-everyone section. I think it
would be logical to put it under the
only-callable-by-sink-implementation section, but maybe there are
reasons why that can't be done (like the jack detection being
implemented outside the alsa modules).

-- 
Tanu