rsi: Add usb multi-byte read operation

USB multibyte read will be used in the new firmware loading method
for RS9113 chipset.
Signed-off-by: Prameela Rani Garnepudi <prameela.j04cs@gmail.com>
Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/rsi/rsi_91x_usb.c

@@ -276,6 +276,46 @@ static int rsi_rx_urb_submit(struct rsi_hw *adapter)
 	return status;
 }
 
+static int rsi_usb_read_register_multiple(struct rsi_hw *adapter, u32 addr,
+					  u8 *data, u16 count)
+{
+	struct rsi_91x_usbdev *dev = (struct rsi_91x_usbdev *)adapter->rsi_dev;
+	u8 *buf;
+	u16 transfer;
+	int status;
+
+	if (!addr)
+		return -EINVAL;
+
+	buf = kzalloc(RSI_USB_BUF_SIZE, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	while (count) {
+		transfer = min_t(u16, count, RSI_USB_BUF_SIZE);
+		status = usb_control_msg(dev->usbdev,
+					 usb_rcvctrlpipe(dev->usbdev, 0),
+					 USB_VENDOR_REGISTER_READ,
+					 RSI_USB_REQ_IN,
+					 ((addr & 0xffff0000) >> 16),
+					 (addr & 0xffff), (void *)buf,
+					 transfer, USB_CTRL_GET_TIMEOUT);
+		if (status < 0) {
+			rsi_dbg(ERR_ZONE,
+				"Reg read failed with error code :%d\n",
+				 status);
+			kfree(buf);
+			return status;
+		}
+		memcpy(data, buf, transfer);
+		count -= transfer;
+		data += transfer;
+		addr += transfer;
+	}
+	kfree(buf);
+	return 0;
+}
+
 /**
  * rsi_usb_write_register_multiple() - This function writes multiple bytes of
  *				       information to multiple registers.