lur: change new_from_hidraw to return an errno

Makes debugging slightly more useful than just returning NULL.

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

src/liblur.c

@@ -24,6 +24,7 @@
  */
 
 #include <assert.h>
+#include <errno.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <sys/ioctl.h>
@@ -141,13 +142,13 @@ hidpp10_init(int fd)
 				  HIDPP10_PROFILE_UNKNOWN);
 }
 
-_EXPORT_ struct lur_receiver*
-lur_receiver_new_from_hidraw(int fd, void *userdata)
+_EXPORT_ int
+lur_receiver_new_from_hidraw(int fd, void *userdata, struct lur_receiver **out)
 {
 	struct lur_receiver *receiver;
 
 	if (!hidraw_is_receiver(fd))
-		return NULL;
+		return -EINVAL;
 
 	receiver = zalloc(sizeof(*receiver));
 	receiver->refcount = 1;
@@ -159,11 +160,12 @@ lur_receiver_new_from_hidraw(int fd, void *userdata)
 	if (!receiver->hidppdev)
 		goto error;
 
-	return receiver;
+	*out = receiver;
+	return 0;
 
 error:
 	free(receiver);
-	return NULL;
+	return -errno;
 
 }
 

src/liblur.h

@@ -107,11 +107,13 @@ lur_is_receiver(uint16_t vid, uint16_t pid);
  *
  * @param fd An O_RDWR file descriptor pointing to a /dev/hidraw node
  * @param userdata Caller-specific data
+ * @param lur Set to the lur object on success, otherwise unmodified
  *
- * @return A lur object, or NULL on error.
+ * @return 0 on success or a negative errno on error
+ * @retval -EINVAL The fd does not point to a lur receiver
  */
-struct lur_receiver*
-lur_receiver_new_from_hidraw(int fd, void *userdata);
+int
+lur_receiver_new_from_hidraw(int fd, void *userdata, struct lur_receiver **lur);
 
 /**
  * Enumerate devices currently paired with the given receiver.

tools/lur-command.c

@@ -41,8 +41,9 @@ enum options {
 static struct lur_receiver *
 open_receiver(const char *path)
 {
-	struct lur_receiver *receiver;
+	struct lur_receiver *receiver = NULL;
 	int fd = -1;
+	int rc;
 
 	fd = open(path, O_RDWR);
 	if (fd < 0) {
@@ -50,8 +51,8 @@ open_receiver(const char *path)
 		return NULL;
 	}
 
-	receiver = lur_receiver_new_from_hidraw(fd, NULL);
-	if (!receiver)
+	rc = lur_receiver_new_from_hidraw(fd, NULL, &receiver);
+	if (rc != 0)
 		close(fd);
 
 	return receiver;