usb: gadget: u_serial: add .get_icount() support

Add icount support for the transmitting and receiving characters. This
will make the tty LED trigger work with the ttyGS devices.

Signed-off-by: Michael Walle <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/gadget/function/u_serial.c

···
 #include <linux/kthread.h>
 #include <linux/workqueue.h>
 #include <linux/kfifo.h>
+#include <linux/serial.h>
 
 #include "u_serial.h"
 
···
 	wait_queue_head_t	close_wait;
 	bool			suspended;	/* port suspended */
 	bool			start_delayed;	/* delay start when suspended */
+	struct async_icount	icount;
 
 	/* REVISIT this state ... */
 	struct usb_cdc_line_coding port_line_coding;	/* 8-N-1 etc */
···
 			break;
 		}
 		do_tty_wake = true;
+		port->icount.tx += len;
 
 		req->length = len;
 		list_del(&req->list);
···
 				size -= n;
 			}
 
+			port->icount.rx += size;
 			count = tty_insert_flip_string(&port->port, packet,
 					size);
 			if (count)
···
 	return status;
 }
 
+static int gs_get_icount(struct tty_struct *tty,
+			 struct serial_icounter_struct *icount)
+{
+	struct gs_port *port = tty->driver_data;
+	struct async_icount cnow;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->port_lock, flags);
+	cnow = port->icount;
+	spin_unlock_irqrestore(&port->port_lock, flags);
+
+	icount->rx = cnow.rx;
+	icount->tx = cnow.tx;
+
+	return 0;
+}
+
 static const struct tty_operations gs_tty_ops = {
 	.open =			gs_open,
 	.close =		gs_close,
···
 	.chars_in_buffer =	gs_chars_in_buffer,
 	.unthrottle =		gs_unthrottle,
 	.break_ctl =		gs_break_ctl,
+	.get_icount =		gs_get_icount,
 };
 
 /*-------------------------------------------------------------------------*/