mixer: Add "disabled" mixer_type.

doc/mpd.conf.5

@@ -163,7 +163,7 @@ Linear interpolator, very fast, poor quality.
 For an up-to-date list of available converters, please see the libsamplerate
 documentation (available online at <\fBhttp://www.mega-nerd.com/SRC/\fP>).
 .TP
-.B mixer_type <alsa, oss, software or hardware>
+.B mixer_type <alsa, oss, software, hardware or disabled>
 This specifies which mixer to use.  The default is hardware and depends on
 what audio output support mpd was built with. Options alsa and oss are
 legacy and should not be used in new configs, but when set mixer_device

doc/mpdconf.example

@@ -245,6 +245,10 @@ log_file			"~/.mpd/log"
 #
 #mixer_type			"software"
 #
+# This example will not allow MPD to touch the mixer at all.
+#
+#mixer_type			"disabled"
+#
 ###############################################################################
 
 

src/volume.c

@@ -36,6 +36,7 @@
 
 #define VOLUME_MIXER_TYPE_SOFTWARE		0
 #define VOLUME_MIXER_TYPE_HARDWARE		1
+#define VOLUME_MIXER_TYPE_DISABLED		2
 
 #define VOLUME_MIXER_SOFTWARE_DEFAULT		""
 #define SW_VOLUME_STATE                         "sw_volume: "
@@ -131,6 +132,8 @@ void volume_init(void)
 	if (param) {
 		if (strcmp(param->value, VOLUME_MIXER_SOFTWARE) == 0) {
 			volume_mixer_type = VOLUME_MIXER_TYPE_SOFTWARE;
+		} else if (strcmp(param->value, VOLUME_MIXER_DISABLED) == 0) {
+			volume_mixer_type = VOLUME_MIXER_TYPE_DISABLED;
 		} else if (strcmp(param->value, VOLUME_MIXER_HARDWARE) == 0) {
 			//nothing to do
 		} else {

src/volume.h

@@ -25,6 +25,7 @@
 #define VOLUME_MIXER_ALSA	"alsa"
 #define VOLUME_MIXER_SOFTWARE	"software"
 #define VOLUME_MIXER_HARDWARE	"hardware"
+#define VOLUME_MIXER_DISABLED	"disabled"
 
 void volume_init(void);