Added C API for managing wakelocks

Simple wrappers for writing to /sys/power/wake_(lock|unlock) files.

libwakelock.c

@@ -0,0 +1,106 @@
+/* ------------------------------------------------------------------------- *
+ * Copyright (C) 2012 Jolla Ltd.
+ * Contact: Simo Piiroinen <simo.piiroinen@jollamobile.com>
+ * License: LGPLv2
+ * ------------------------------------------------------------------------- */
+
+#include "libwakelock.h"
+
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+
+/** Whether to write debug logging to stderr
+ *
+ * If not enabled, no diagnostics of any kind gets written.
+ */
+#ifndef LWL_ENABLE_LOGGING
+# define LWL_ENABLE_LOGGING 01
+#endif
+
+/** Prefix used for log messages
+ */
+#define LWL_LOG_PFIX "LWL: "
+
+/** Logging functionality that can be configured out at compile time
+ */
+#if LWL_ENABLE_LOGGING
+# define lwl_debugf(FMT, ARGS...) fprintf(stderr, LWL_LOG_PFIX FMT, ##ARGS)
+#else
+# define lwl_debugf(FMT, ARGS...) do { } while( 0 )
+#endif
+
+/** Paths to wakelock interfaces in sysfs
+ */
+static const char lwl_lock_path[]   = "/sys/power/wake_lock";
+static const char lwl_unlock_path[] = "/sys/power/wake_unlock";
+
+/** Helper for writing to sysfs files
+ */
+static void lwl_write_file(const char *path, const char *data)
+{
+	int file;
+
+	lwl_debugf("%s << %s", path, data);
+
+	if( (file = TEMP_FAILURE_RETRY(open(path, O_WRONLY))) == -1 ) {
+		lwl_debugf("%s: open: %m\n", path);
+	} else {
+		int size = strlen(data);
+		errno = 0;
+		if( TEMP_FAILURE_RETRY(write(file, data, size)) != size ) {
+			lwl_debugf("%s: write: %m\n", path);
+		}
+		TEMP_FAILURE_RETRY(close(file));
+	}
+}
+
+/** Helper for checking if wakelock interface is supported
+ */
+static int lwl_enabled(void)
+{
+	static int checked = 0, enabled = 0;
+
+	if( !checked ) {
+		checked = 1, enabled = !access(lwl_lock_path, F_OK);
+		lwl_debugf("%s\n", enabled ? "enabled" : "disabled");
+	}
+
+	return enabled;
+}
+
+/** Use sysfs interface to create and enable a wakelock.
+ *
+ * @param name The name of the wakelock to obtain
+ * @param ns   Time in nanoseconds before the wakelock gets released
+ *             automatically, or negative value for no timeout.
+ */
+void wakelock_lock(const char *name, long long ns)
+{
+	if( lwl_enabled() ) {
+		char tmp[64];
+		if( ns < 0 ) {
+			snprintf(tmp, sizeof tmp, "%s\n", name);
+		} else {
+			snprintf(tmp, sizeof tmp, "%s %lld\n", name, ns);
+		}
+		lwl_write_file(lwl_lock_path, tmp);
+	}
+}
+
+/** Use sysfs interface to disable a wakelock.
+ *
+ * @param name The name of the wakelock to release
+ *
+ * Note: This will not delete the wakelocks.
+ */
+void wakelock_unlock(const char *name)
+{
+	if( lwl_enabled() ) {
+		char tmp[64];
+		snprintf(tmp, sizeof tmp, "%s\n", name);
+		lwl_write_file(lwl_unlock_path, tmp);
+	}
+}

libwakelock.h

@@ -0,0 +1,23 @@
+/* ------------------------------------------------------------------------- *
+ * Copyright (C) 2012 Jolla Ltd.
+ * Contact: Simo Piiroinen <simo.piiroinen@jollamobile.com>
+ * License: LGPLv2
+ * ------------------------------------------------------------------------- */
+
+#ifndef LIBWAKELOCK_H_
+# define LIBWAKELOCK_H_
+
+# ifdef __cplusplus
+extern "C" {
+# elif 0
+};
+# endif
+
+void wakelock_lock  (const char *name, long long ns);
+void wakelock_unlock(const char *name);
+
+# ifdef __cplusplus
+};
+# endif
+
+#endif /* LIBWAKELOCK_H_ */