Split libevdev_new() into _new and _new_from_fd()

libevdev_new() can only fail on allocation failures, but with an fd the
failure options are more. Split into a new function that can return an error
code.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

libevdev/libevdev.c

@@ -144,24 +144,39 @@ libevdev_noop_log_func(const char *format, va_list args)
 }
 
 struct libevdev*
-libevdev_new(int fd)
+libevdev_new(void)
 {
 	struct libevdev *dev;
 
 	dev = calloc(1, sizeof(*dev));
 	if (!dev)
 		return NULL;
+	dev->fd = -1;
 	dev->num_slots = -1;
 	dev->current_slot = -1;
 	dev->log = libevdev_noop_log_func;
 
-	if (fd >= 0)
-		libevdev_set_fd(dev, fd);
-	dev->fd = fd;
-
 	return dev;
 }
 
+int
+libevdev_new_from_fd(int fd, struct libevdev **dev)
+{
+	struct libevdev *d;
+	int rc;
+
+	d = libevdev_new();
+	if (!d)
+		return -ENOSPC;
+
+	rc = libevdev_set_fd(d, fd);
+	if (rc < 0)
+		libevdev_free(d);
+	else
+		*dev = d;
+	return rc;
+}
+
 void
 libevdev_free(struct libevdev *dev)
 {

libevdev/libevdev.h

@@ -34,14 +34,29 @@ enum EvdevReadFlags {
 
 
 /**
- * Initialize a new libevdev struct.
- *
- * @param fd If fd >= 0, the device is initialised for the fd. Otherwise, a
- * caller must call evdev_set_fd() before attempting to read events.
+ * Initialize a new libevdev device.
 *
  * @see libevdev_set_fd
  */
-struct libevdev* libevdev_new(int fd);
+struct libevdev* libevdev_new(void);
+
+/**
+ * Initialize a new libevdev device from the given fd.
+ *
+ * This is a shortcut for
+ *
+ * <pre>
+ * struct libevdev *dev = libevdev_new();
+ * libevdev_set_fd(dev, fd);
+ * </pre>
+ *
+ * @param fd A file descriptor to the device in O_RDWR or O_RDONLY mode.
+ *
+ * @return On success, zero is returned and dev is set to the newly
+ * allocated struct. On failure, a negative errno is returned and the value
+ * of dev is undefined.
+ */
+int libevdev_new_from_fd(int fd, struct libevdev **dev);
 
 /**
  * Clean up and free the libevdev struct.

test/libevdev-events.c

@@ -90,9 +90,9 @@ main(int argc, char **argv)
 		goto out;
 	}
 
-	dev = libevdev_new(fd);
-	if (!dev) {
-		fprintf(stderr, "Failed to init libevdev\n");
+	rc = libevdev_new_from_fd(fd, &dev);
+	if (rc < 0) {
+		fprintf(stderr, "Failed to init libevdev (%s)\n", strerror(-rc));
 		goto out;
 	}
 

test/libevdev-print.c

@@ -23,6 +23,7 @@
 #include <config.h>
 
 #include <stdio.h>
+#include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -111,6 +112,7 @@ main(int argc, char **argv)
 	struct libevdev *dev;
 	const char *file;
 	int fd;
+	int rc;
 
 
 	if (argc < 2)
@@ -123,9 +125,9 @@ main(int argc, char **argv)
 		return 1;
 	}
 
-	dev = libevdev_new(fd);
-	if (!dev) {
-		fprintf(stderr, "Failed to init libevdev\n");
+	rc = libevdev_new_from_fd(fd, &dev);
+	if (rc < 0) {
+		fprintf(stderr, "Failed to init libevdev (%s)\n", strerror(-rc));
 		return 1;
 	}