cpu_freq: Port to OpenBSD

In OpenBSD CPU frequency gets fetched using sysctl now.

README

@@ -62,7 +62,7 @@ Porting to OpenBSD is the current goal before thinking about a release.
 
 The following functions are not portable at the moment:
 - wifi_{perc,essid}
-- cpu_{freq,perc,iowait}
+- cpu_{perc,iowait}
 - entropy
 - swap_{free,perc,total,used}
 - battery_{power,state}

components/cpu.c

@@ -1,10 +1,14 @@
 /* See LICENSE file for copyright and license details. */
-#if defined(__linux__)
+#include <errno.h>
 #include <stdio.h>
 #include <string.h>
+#if defined(__OpenBSD__)
+#include <sys/sysctl.h>
+#endif
 
 #include "../util.h"
 
+#if defined(__linux__)
 const char *
 cpu_freq(void)
 {
@@ -62,4 +66,23 @@ cpu_iowait(void)
 
 	return bprintf("%d", perc);
 }
+#elif defined(__OpenBSD__)
+const char *
+cpu_freq(void)
+{
+	int freq, mib[2];
+	size_t size;
+
+	mib[0] = CTL_HW;
+	mib[1] = HW_CPUSPEED;
+
+	size = sizeof(freq);
+
+	if (sysctl(mib, 2, &freq, &size, NULL, 0) == -1) {
+		fprintf(stderr, "sysctl 'HW_CPUSPEED': %s\n", strerror(errno));
+		return NULL;
+	}
+
+	return bprintf("%d", freq);
+}
 #endif