return (unsigned int) numwrite;
}
+/*
+ * Detect whether a CPU is online
+ *
+ * Returns:
+ * 1 -> if CPU is online
+ * 0 -> if CPU is offline
+ * negative errno values in error case
+ */
+int sysfs_is_cpu_online(unsigned int cpu)
+{
+ char path[SYSFS_PATH_MAX];
+ int fd;
+ ssize_t numread;
+ unsigned long long value;
+ char linebuf[MAX_LINE_LEN];
+ char *endp;
+ struct stat statbuf;
+
+ snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u", cpu);
+
+ if (stat(path, &statbuf) != 0)
+ return 0;
+
+ /*
+ * kernel without CONFIG_HOTPLUG_CPU
+ * -> cpuX directory exists, but not cpuX/online file
+ */
+ snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/online", cpu);
+ if (stat(path, &statbuf) != 0)
+ return 1;
+
+ fd = open(path, O_RDONLY);
+ if (fd == -1)
+ return -errno;
+
+ numread = read(fd, linebuf, MAX_LINE_LEN - 1);
+ if (numread < 1) {
+ close(fd);
+ return -EIO;
+ }
+ linebuf[numread] = '\0';
+ close(fd);
+
+ value = strtoull(linebuf, &endp, 0);
+ if (value > 1 || value < 0)
+ return -EINVAL;
+
+ return value;
+}
+
/* CPUidle idlestate specific /sys/devices/system/cpu/cpuX/cpuidle/ access */
/*