Mark unused parameters, fix compiler warnings

components/battery.c

@@ -52,11 +52,13 @@
 	#include <unistd.h>
 
 	const char *
-	battery_perc(const char *null)
+	battery_perc(const char *bat)
 	{
 		struct apm_power_info apm_info;
 		int fd;
 
+		UNUSED(bat); /* no way to specify battery on OpenBSD */
+
 		fd = open("/dev/apm", O_RDONLY);
 		if (fd < 0) {
 			fprintf(stderr, "open '/dev/apm': %s\n", strerror(errno));
@@ -88,6 +90,8 @@
 			{ APM_AC_OFF,     "-" },
 		};
 
+		UNUSED(bat); /* no way to specify battery on OpenBSD */
+
 		fd = open("/dev/apm", O_RDONLY);
 		if (fd < 0) {
 			fprintf(stderr, "open '/dev/apm': %s\n", strerror(errno));

components/temperature.c

@@ -21,12 +21,14 @@
 	#include <sys/sysctl.h>
 
 	const char *
-	temp(const char *null)
+	temp(const char *file)
 	{
 		int mib[5];
 		size_t size;
 		struct sensor temp;
 
+		UNUSED(file); /* no temperature file on OpenBSD */
+
 		mib[0] = CTL_HW;
 		mib[1] = HW_SENSORS;
 		mib[2] = 0; /* cpu0 */

util.h

@@ -3,5 +3,7 @@ extern char buf[1024];
 
 #define LEN(x) (sizeof (x) / sizeof *(x))
 
+#define UNUSED(x) (void)x
+
 const char *bprintf(const char *fmt, ...);
 int pscanf(const char *path, const char *fmt, ...);