ALSA: Build jack detection

Since jack detection requires the input subsystem which may not be
desired on small systems it is not built unless required by a driver
that is being built. Drivers using jack detection should use a pattern
like this:

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

to ensure that the jack detection API is enabled if the input subsystem
is.  If the input subsystem is not enabled then a stub version of the
API is provided.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

sound/core/Kconfig

@@ -12,6 +12,12 @@ config SND_HWDEP
 config SND_RAWMIDI
 	tristate
 
+# To be effective this also requires INPUT - users should say:
+#    select SND_JACK if INPUT=y || INPUT=SND
+# to avoid having to force INPUT on.
+config SND_JACK
+	bool
+
 config SND_SEQUENCER
 	tristate "Sequencer support"
 	select SND_TIMER

sound/core/Makefile

@@ -7,6 +7,7 @@ snd-y     := sound.o init.o memory.o info.o control.o misc.o device.o
 snd-$(CONFIG_ISA_DMA_API) += isadma.o
 snd-$(CONFIG_SND_OSSEMUL) += sound_oss.o info_oss.o
 snd-$(CONFIG_SND_VMASTER) += vmaster.o
+snd-$(CONFIG_SND_JACK)	  += jack.o
 
 snd-pcm-objs := pcm.o pcm_native.o pcm_lib.o pcm_timer.o pcm_misc.o \
 		pcm_memory.o