usb: gadget: f_midi: eliminate abuse of ep->driver data

Since ep->driver_data is not used for endpoint claiming, neither for
enabled/disabled state storing, we can reduce number of places where
we read or modify it's value, as now it has no particular meaning for
function or framework logic.

In case of f_midi we only need to store in ep->driver_data pointer to
struct f_midi, as it's used in f_midi_complete() callback and related
functions. All other uses of ep->driver_data are now meaningless and
can be safely removed.
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/function/f_midi.c

@@ -302,8 +302,7 @@ static int f_midi_start_ep(struct f_midi *midi,
 	int err;
 	struct usb_composite_dev *cdev = f->config->cdev;
 
-	if (ep->driver_data)
-		usb_ep_disable(ep);
+	usb_ep_disable(ep);
 
 	err = config_ep_by_speed(midi->gadget, f, ep);
 	if (err) {
@@ -341,8 +340,7 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 	if (err)
 		return err;
 
-	if (midi->out_ep->driver_data)
-		usb_ep_disable(midi->out_ep);
+	usb_ep_disable(midi->out_ep);
 
 	err = config_ep_by_speed(midi->gadget, f, midi->out_ep);
 	if (err) {
@@ -763,12 +761,10 @@ static int f_midi_bind(struct usb_configuration *c, struct usb_function *f)
 	midi->in_ep = usb_ep_autoconfig(cdev->gadget, &bulk_in_desc);
 	if (!midi->in_ep)
 		goto fail;
-	midi->in_ep->driver_data = cdev;	/* claim */
 
 	midi->out_ep = usb_ep_autoconfig(cdev->gadget, &bulk_out_desc);
 	if (!midi->out_ep)
 		goto fail;
-	midi->out_ep->driver_data = cdev;	/* claim */
 
 	/* allocate temporary function list */
 	midi_function = kcalloc((MAX_PORTS * 4) + 9, sizeof(*midi_function),
@@ -895,12 +891,6 @@ static int f_midi_bind(struct usb_configuration *c, struct usb_function *f)
 fail:
 	f_midi_unregister_card(midi);
 fail_register:
-	/* we might as well release our claims on endpoints */
-	if (midi->out_ep)
-		midi->out_ep->driver_data = NULL;
-	if (midi->in_ep)
-		midi->in_ep->driver_data = NULL;
-
 	ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
 
 	return status;