usb: gadget: add 'quirk_zlp_not_supp' to usb_gadget

Due to some UDC controllers may not support zlp, usb gadget layer
needs to provide a generic way to inform gadget functions about non-standard
hardware limitations.

This patch adds 'quirk_zlp_not_supp' field to struct usb_gadget and helper
function gadget_is_zlp_supported(). It also sets 'quirk_zlp_not_supp'
to 1 in musb UDC driver, which has such limitation.

[ balbi@ti.com : make it build ]
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_gadget.c

@@ -2075,6 +2075,7 @@ __acquires(musb->lock)
 	musb->g.b_hnp_enable = 0;
 	musb->g.a_alt_hnp_support = 0;
 	musb->g.a_hnp_support = 0;
+	musb->g.quirk_zlp_not_supp = 1;
 
 	/* Normal reset, as B-Device;
 	 * or else after HNP, as A-Device

include/linux/usb/gadget.h

@@ -574,6 +574,7 @@ struct usb_gadget {
 	unsigned			quirk_ep_out_aligned_size:1;
 	unsigned			quirk_altset_not_supp:1;
 	unsigned			quirk_stall_not_supp:1;
+	unsigned			quirk_zlp_not_supp:1;
 	unsigned			is_selfpowered:1;
 	unsigned			deactivated:1;
 	unsigned			connected:1;
@@ -630,6 +631,15 @@ static inline int gadget_is_stall_supported(struct usb_gadget *g)
 	return !g->quirk_stall_not_supp;
 }
 
+/**
+ * gadget_is_zlp_supported - return true iff the hardware supports zlp
+ * @g: controller to check for quirk
+ */
+static inline int gadget_is_zlp_supported(struct usb_gadget *g)
+{
+	return !g->quirk_zlp_not_supp;
+}
+
 /**
  * gadget_is_dualspeed - return true iff the hardware handles high speed
  * @g: controller that might support both high and full speeds