At Tue, 3 Jun 2008 11:40:48 +0100,
Mark Brown wrote:

The following couple of patches update the jack reporting API I posted
last week with the feedback I have received so far.  The changes since
the last submision are:

 - Addition of snd_jack_set_parent(), allowing drivers to override the
   default parent for the input device prior to registration.
 - The jack detection support is now included unconditionally in ALSA,
   requiring a dependency on the input subsystem.

I'm not entirely happy with making ALSA depend on input but given that
it is only optional on embedded systems and that the input core is not
that large it seemed the best way of ensuring that the input subsystem
is available for the jack API without hassle for drivers using it,
especially given the lack of dependency propagation from select.

I also feel uneasy that it's built in unconditionally and requires an 
additional dependency on CONFIG_INPUT.  The fact that both SND and
INPUT can be modules makes things a bit complicated.

As a workaround, how about to select with "if" conditions?
For example, in sound/core/Kconfig,

config SND_JACK
	bool

while the driver requires SND_JACK has the below:

config SND_FOO
	tristate "..."
	...
	select SND_JACK if INPUT=y || INPUT=SND

Yeah, it looks horrible at a first glance, but it's a known workaround
for reverse selections...

In sound/core/Makefile, just add the line:

snd-$(CONFIG_SND_JACK) += jack.o

so that the code is built into snd module only when necessary.

Also, sound/jack.h should provide empty inline functions for the case 
CONFIG_SND_JACK=n.  Then you'll be able to reduce ifdefs in the driver
codes.


thanks,

Takashi