ALSA: usb-audio: Pass direct struct pointer instead of list_head

Some functions in mixer.c and endpoint.c receive list_head instead of
the object itself.  This is not obvious and rather error-prone.  Let's
pass the proper object directly instead.

The functions in midi.c still receive list_head and this can't be
changed since the object definition isn't exposed to the outside of
midi.c, so left as is.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/card.c

@@ -114,13 +114,11 @@ static struct usb_driver usb_audio_driver;
  * disconnect streams
  * called from usb_audio_disconnect()
  */
-static void snd_usb_stream_disconnect(struct list_head *head)
+static void snd_usb_stream_disconnect(struct snd_usb_stream *as)
 {
 	int idx;
-	struct snd_usb_stream *as;
 	struct snd_usb_substream *subs;
 
-	as = list_entry(head, struct snd_usb_stream, list);
 	for (idx = 0; idx < 2; idx++) {
 		subs = &as->substream[idx];
 		if (!subs->num_formats)
@@ -307,10 +305,10 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 
 static int snd_usb_audio_free(struct snd_usb_audio *chip)
 {
-	struct list_head *p, *n;
+	struct snd_usb_endpoint *ep, *n;
 
-	list_for_each_safe(p, n, &chip->ep_list)
-		snd_usb_endpoint_free(p);
+	list_for_each_entry_safe(ep, n, &chip->ep_list, list)
+		snd_usb_endpoint_free(ep);
 
 	mutex_destroy(&chip->mutex);
 	kfree(chip);
@@ -609,12 +607,14 @@ static void usb_audio_disconnect(struct usb_interface *intf)
 	mutex_lock(&register_mutex);
 	chip->num_interfaces--;
 	if (chip->num_interfaces <= 0) {
+		struct snd_usb_stream *as;
 		struct snd_usb_endpoint *ep;
+		struct usb_mixer_interface *mixer;
 
 		snd_card_disconnect(card);
 		/* release the pcm resources */
-		list_for_each(p, &chip->pcm_list) {
-			snd_usb_stream_disconnect(p);
+		list_for_each_entry(as, &chip->pcm_list, list) {
+			snd_usb_stream_disconnect(as);
 		}
 		/* release the endpoint resources */
 		list_for_each_entry(ep, &chip->ep_list, list) {
@@ -625,8 +625,8 @@ static void usb_audio_disconnect(struct usb_interface *intf)
 			snd_usbmidi_disconnect(p);
 		}
 		/* release mixer resources */
-		list_for_each(p, &chip->mixer_list) {
-			snd_usb_mixer_disconnect(p);
+		list_for_each_entry(mixer, &chip->mixer_list, list) {
+			snd_usb_mixer_disconnect(mixer);
 		}
 		usb_chip[chip->index] = NULL;
 		mutex_unlock(&register_mutex);

sound/usb/endpoint.c

@@ -1002,15 +1002,12 @@ void snd_usb_endpoint_release(struct snd_usb_endpoint *ep)
 /**
  * snd_usb_endpoint_free: Free the resources of an snd_usb_endpoint
  *
- * @ep: the list header of the endpoint to free
+ * @ep: the endpoint to free
  *
  * This free all resources of the given ep.
  */
-void snd_usb_endpoint_free(struct list_head *head)
+void snd_usb_endpoint_free(struct snd_usb_endpoint *ep)
 {
-	struct snd_usb_endpoint *ep;
-
-	ep = list_entry(head, struct snd_usb_endpoint, list);
 	kfree(ep);
 }
 

sound/usb/endpoint.h

@@ -24,7 +24,7 @@ void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep);
 int  snd_usb_endpoint_activate(struct snd_usb_endpoint *ep);
 void snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep);
 void snd_usb_endpoint_release(struct snd_usb_endpoint *ep);
-void snd_usb_endpoint_free(struct list_head *head);
+void snd_usb_endpoint_free(struct snd_usb_endpoint *ep);
 
 int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep);
 int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep);

sound/usb/mixer.c

@@ -2483,11 +2483,8 @@ int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif,
 	return err;
 }
 
-void snd_usb_mixer_disconnect(struct list_head *p)
+void snd_usb_mixer_disconnect(struct usb_mixer_interface *mixer)
 {
-	struct usb_mixer_interface *mixer;
-
-	mixer = list_entry(p, struct usb_mixer_interface, list);
 	usb_kill_urb(mixer->urb);
 	usb_kill_urb(mixer->rc_urb);
 }

sound/usb/mixer.h

@@ -57,7 +57,7 @@ struct usb_mixer_elem_info {
 
 int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif,
 			 int ignore_error);
-void snd_usb_mixer_disconnect(struct list_head *p);
+void snd_usb_mixer_disconnect(struct usb_mixer_interface *mixer);
 
 void snd_usb_mixer_notify_id(struct usb_mixer_interface *mixer, int unitid);