cpupower: Add is_valid_path API

Add is_valid_path API to check whether the sysfs file is present or not.

Suggested-by: Gautham R. Shenoy <[e-mail]>
Reviewed-by: Mario Limonciello <[e-mail]>
Signed-off-by: Wyes Karny <[e-mail]>
Tested-by: Perry Yuan <[e-mail]>
Acked-by: Huang Rui <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/power/cpupower/lib/cpupower.c

···
 #include "cpupower.h"
 #include "cpupower_intern.h"
 
+int is_valid_path(const char *path)
+{
+	if (access(path, F_OK) == -1)
+		return 0;
+	return 1;
+}
+
 unsigned int cpupower_read_sysfs(const char *path, char *buf, size_t buflen)
 {
 	ssize_t numread;

tools/power/cpupower/lib/cpupower_intern.h

···
 
 #define SYSFS_PATH_MAX 255
 
+int is_valid_path(const char *path);
 unsigned int cpupower_read_sysfs(const char *path, char *buf, size_t buflen);
 unsigned int cpupower_write_sysfs(const char *path, char *buf, size_t buflen);