alsactl: systemd and udev hookup

Add minimal systemd and udev support to alsactl so that mixer settings
are restored at boot, when sound cards are plugged in and saved on
shutdown.

This is similar to existing udev/init script solutions in various
distributions.

Note that alsactl is called both synchronously from the udev rules as
well as asynchronously at boot. This is intended, and to ensure two
things:

- At boot the asound.state file might not be readable, since it resides
  on a different file system. That means exclusively restoring sound card
  settings from udev rules will no suffice, since if the rule is
  executed at early boot (for example within udev settle) then the file
  will no be readable and cannot be restored.

- We need to ensure that applications monitoring sound cards coming and
  going (such as PA) must not get these events before the mixer settings
  have been restored. That means the mixer settings must be restored
  synchronously withing the udev rules, before the events are passed on
  to the apps.

That basically means we need to restore the settings once in udev, to
deal with sound cards becoming available during runtime. And once in
early boot to deal with coldplugged soundcards whose data files might
not have been available at time of plugging. Hence we call alsactl
twice: one from the udev rule, and once from he systemd unit file.

Signed-off-by: Lennart Poettering <mznyfn@0pointer.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

Makefile.am

@@ -37,3 +37,6 @@ dist-hook:
 	else \
 		$(TAR) --create --verbose --file=- $(distdir) | bzip2 -c -9 > $(distdir).tar.bz2 ; \
 	fi
+
+DISTCHECK_CONFIGURE_FLAGS = \
+        --with-systemdsystemunitdir=$$dc_install_base/$(systemdsystemunitdir)

alsactl/.gitignore

@@ -0,0 +1,3 @@
+alsa-store.service
+alsa-restore.service
+90-alsa-restore.rules

alsactl/90-alsa-restore.rules.in

@@ -0,0 +1,2 @@
+ACTION=="add", SUBSYSTEM=="sound", KERNEL=="controlC*", KERNELS=="card*", \
+        RUN+="@sbindir@/alsactl restore $attr{number}"

alsactl/Makefile.am

@@ -10,5 +10,51 @@ EXTRA_DIST=alsactl.1 alsactl_init.xml
 alsactl_SOURCES=alsactl.c state.c utils.c init_parse.c
 noinst_HEADERS=alsactl.h list.h init_sysdeps.c init_utils_string.c init_utils_run.c init_sysfs.c
 
+udevrulesdir=/lib/udev/rules.d
+
+dist_udevrules_DATA = \
+	90-alsa-restore.rules
+
+if HAVE_SYSTEMD
+
+systemdsystemunit_DATA = \
+	alsa-store.service \
+	alsa-restore.service
+
+install-data-hook:
+	$(MKDIR_P) -m 0755 \
+		$(DESTDIR)$(systemdsystemunitdir)/basic.target.wants \
+		$(DESTDIR)$(systemdsystemunitdir)/shutdown.target.wants
+	( cd $(DESTDIR)$(systemdsystemunitdir)/basic.target.wants && \
+	        rm -f alsa-restore.service && \
+		$(LN_S) ../alsa-restore.service alsa-restore.service )
+	( cd $(DESTDIR)$(systemdsystemunitdir)/shutdown.target.wants && \
+	        rm -f alsa-store.service && \
+		$(LN_S) ../alsa-store.service alsa-store.service )
+
+endif
+
+edit = \
+	sed $(SED) -r 's,@sbindir\@,$(sbindir),g' < $< > $@ || rm $@
+
+alsa-store.service: alsa-store.service.in
+	$(edit)
+
+alsa-restore.service: alsa-restore.service.in
+	$(edit)
+
+90-alsa-restore.rules: 90-alsa-restore.rules.in
+	$(edit)
+
+EXTRA_DIST += \
+	alsa-store.service.in \
+	alsa-restore.service.in \
+	90-alsa-restore.rules.in
+
+CLEANFILES = \
+	alsa-store.service \
+	alsa-restore.service \
+	90-alsa-restore.rules
+
 %.7: %.xml
 	xmlto man $?

alsactl/alsa-restore.service.in

@@ -0,0 +1,11 @@
+[Unit]
+Description=Restore Sound Card State
+DefaultDependencies=no
+After=sysinit.target
+Before=shutdown.target
+Conflicts=shutdown.target
+
+[Service]
+Type=oneshot
+ExecStart=-@sbindir@/alsactl restore
+StandardOutput=syslog

alsactl/alsa-store.service.in

@@ -0,0 +1,9 @@
+[Unit]
+Description=Store Sound Card State
+DefaultDependencies=no
+Before=shutdown.target
+
+[Service]
+Type=oneshot
+ExecStart=@sbindir@/alsactl store
+StandardOutput=syslog

configure.in

@@ -26,6 +26,7 @@ fi
 AC_PROG_CC
 dnl AC_PROG_CXX
 AC_PROG_INSTALL
+AC_PROG_MKDIR_P
 AC_PROG_LN_S
 AM_PATH_ALSA(1.0.16)
 
@@ -278,6 +279,16 @@ SAVE_UTIL_VERSION
 
 AC_SUBST(LIBRT)
 
+dnl Check for systemd
+PKG_PROG_PKG_CONFIG
+AC_ARG_WITH([systemdsystemunitdir],
+        AS_HELP_STRING([--with-systemdsystemunitdir=DIR], [Directory for systemd service files]),
+        [], [with_systemdsystemunitdir=$($PKG_CONFIG --variable=systemdsystemunitdir systemd)])
+if test "x$with_systemdsystemunitdir" != xno; then
+        AC_SUBST([systemdsystemunitdir], [$with_systemdsystemunitdir])
+fi
+AM_CONDITIONAL(HAVE_SYSTEMD, [test -n "$with_systemdsystemunitdir" -a "x$with_systemdsystemunitdir" != xno ])
+
 AC_OUTPUT(Makefile alsactl/Makefile alsactl/init/Makefile \
 	  alsamixer/Makefile amidi/Makefile amixer/Makefile \
 	  m4/Makefile po/Makefile.in \