contrib: add example rules script

Makefile

@@ -3,11 +3,13 @@
 
 PREFIX = /usr/local
 LIBDIR = ${PREFIX}/lib
+LIBEXECDIR = ${PREFIX}/libexec
 INCLUDEDIR = ${PREFIX}/include
 PKGCONFIGDIR = ${LIBDIR}/pkgconfig
 XCFLAGS = ${CPPFLAGS} ${CFLAGS} -std=c99 -fPIC -D_XOPEN_SOURCE=700 \
 		  -Wall -Wextra -Wpedantic -Wmissing-prototypes -Wstrict-prototypes \
-		  -Wno-unused-parameter
+		  -Wno-unused-parameter \
+		  -DRULES_HELPER_PATH=\"${LIBEXECDIR}/libudev-zero-rules-helper\"
 XLDFLAGS = ${LDFLAGS} -shared -Wl,-soname,libudev.so.1
 XARFLAGS = -rc
 AR = ar

contrib/libudev-zero-rules-helper.sh

@@ -0,0 +1,15 @@
+#!/bin/sh -e
+
+if [ "$SUBSYSTEM" = "sound" ]
+then
+    if printf '%s' "$SYSNAME" | grep '^card' > /dev/null
+    then
+        printf 'SOUND_INITIALIZED=1\n'
+    fi
+
+    if printf '%s' "$SYSNAME" | grep '^pcmC.*D2c$' > /dev/null \
+        && grep '^AppleJ' "$SYSPATH/device/id" 2>/dev/null
+    then
+        printf 'ACP_IGNORE=1\n'
+    fi
+fi

udev_device.c

@@ -55,7 +55,7 @@
 #endif
 
 #ifndef RULES_HELPER_PATH
-#define RULES_HELPER_PATH "/sbin/libudev-zero-rules-helper"
+#error "RULES_HELPER_PATH not specified"
 #endif
 
 #ifndef UEVENT_NUM_ENVP