usb: gadget: printer: add req_match for printer function

Verify that a given usb_ctrlrequest is meant for printer function.
The following parts of the request are tested:

- bmRequestType:Data transfer direction
- bmRequestType:Type
- bmRequestType:Recipient
- bRequest
- wValue for bRequest 1 and 2
- wLength

Additionally, the request is considered meant for this function
iff the decoded interface number matches dev->interface.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/legacy/printer.c

@@ -974,6 +974,41 @@ static void printer_soft_reset(struct printer_dev *dev)
 
 /*-------------------------------------------------------------------------*/
 
+static bool gprinter_req_match(struct usb_function *f,
+			       const struct usb_ctrlrequest *ctrl)
+{
+	struct printer_dev	*dev = func_to_printer(f);
+	u16			w_index = le16_to_cpu(ctrl->wIndex);
+	u16			w_value = le16_to_cpu(ctrl->wValue);
+	u16			w_length = le16_to_cpu(ctrl->wLength);
+
+	if ((ctrl->bRequestType & USB_RECIP_MASK) != USB_RECIP_INTERFACE ||
+	    (ctrl->bRequestType & USB_TYPE_MASK) != USB_TYPE_CLASS)
+		return false;
+
+	switch (ctrl->bRequest) {
+	case GET_DEVICE_ID:
+		w_index >>= 8;
+		if (w_length <= PNP_STRING_LEN &&
+		    (USB_DIR_IN & ctrl->bRequestType))
+			break;
+		return false;
+	case GET_PORT_STATUS:
+		if (!w_value && w_length == 1 &&
+		    (USB_DIR_IN & ctrl->bRequestType))
+			break;
+		return false;
+	case SOFT_RESET:
+		if (!w_value && !w_length &&
+		   (USB_DIR_OUT & ctrl->bRequestType))
+			break;
+		/* fall through */
+	default:
+		return false;
+	}
+	return w_index == dev->interface;
+}
+
 /*
  * The setup() callback implements all the ep0 functionality that's not
  * handled lower down.
@@ -1251,6 +1286,7 @@ static int f_printer_bind_config(struct usb_configuration *c, char *pnp_str,
 	dev->function.unbind = printer_func_unbind;
 	dev->function.set_alt = printer_func_set_alt;
 	dev->function.disable = printer_func_disable;
+	dev->function.req_match = gprinter_req_match;
 	INIT_LIST_HEAD(&dev->tx_reqs);
 	INIT_LIST_HEAD(&dev->rx_reqs);
 	INIT_LIST_HEAD(&dev->rx_buffers);