tty: Make tiocgicount a handler

Dan Rosenberg noted that various drivers return the struct with uncleared
fields. Instead of spending forever trying to stomp all the drivers that
get it wrong (and every new driver) do the job in one place.

This first patch adds the needed operations and hooks them up, including
the needed USB midlayer and serial core plumbing.

Signed-off-by: Alan Cox <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/char/tty_io.c

···
 #include <linux/bitops.h>
 #include <linux/delay.h>
 #include <linux/seq_file.h>
+#include <linux/serial.h>
 
 #include <linux/uaccess.h>
 #include <asm/system.h>
···
 	return tty->ops->tiocmset(tty, file, set, clear);
 }
 
+static int tty_tiocgicount(struct tty_struct *tty, void __user *arg)
+{
+	int retval = -EINVAL;
+	struct serial_icounter_struct icount;
+	memset(&icount, 0, sizeof(icount));
+	if (tty->ops->get_icount)
+		retval = tty->ops->get_icount(tty, &icount);
+	if (retval != 0)
+		return retval;
+	if (copy_to_user(arg, &icount, sizeof(icount)))
+		return -EFAULT;
+	return 0;
+}
+
 struct tty_struct *tty_pair_get_tty(struct tty_struct *tty)
 {
 	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
···
 	case TIOCMBIC:
 	case TIOCMBIS:
 		return tty_tiocmset(tty, file, cmd, p);
+	case TIOCGICOUNT:
+		retval = tty_tiocgicount(tty, p);
+		/* For the moment allow fall through to the old method */
+        	if (retval != -EINVAL)
+			return retval;
+		break;
 	case TCFLSH:
 		switch (arg) {
 		case TCIFLUSH:

drivers/serial/serial_core.c

···
  * NB: both 1->0 and 0->1 transitions are counted except for
  *     RI where only 0->1 is counted.
  */
-static int uart_get_count(struct uart_state *state,
-			  struct serial_icounter_struct __user *icnt)
+static int uart_get_icount(struct tty_struct *tty,
+			  struct serial_icounter_struct *icount)
 {
-	struct serial_icounter_struct icount;
+	struct uart_state *state = tty->driver_data;
 	struct uart_icount cnow;
 	struct uart_port *uport = state->uart_port;
 
···
 	memcpy(&cnow, &uport->icount, sizeof(struct uart_icount));
 	spin_unlock_irq(&uport->lock);
 
-	icount.cts         = cnow.cts;
-	icount.dsr         = cnow.dsr;
-	icount.rng         = cnow.rng;
-	icount.dcd         = cnow.dcd;
-	icount.rx          = cnow.rx;
-	icount.tx          = cnow.tx;
-	icount.frame       = cnow.frame;
-	icount.overrun     = cnow.overrun;
-	icount.parity      = cnow.parity;
-	icount.brk         = cnow.brk;
-	icount.buf_overrun = cnow.buf_overrun;
+	icount->cts         = cnow.cts;
+	icount->dsr         = cnow.dsr;
+	icount->rng         = cnow.rng;
+	icount->dcd         = cnow.dcd;
+	icount->rx          = cnow.rx;
+	icount->tx          = cnow.tx;
+	icount->frame       = cnow.frame;
+	icount->overrun     = cnow.overrun;
+	icount->parity      = cnow.parity;
+	icount->brk         = cnow.brk;
+	icount->buf_overrun = cnow.buf_overrun;
 
-	return copy_to_user(icnt, &icount, sizeof(icount)) ? -EFAULT : 0;
+	return 0;
 }
 
 /*
···
 	switch (cmd) {
 	case TIOCMIWAIT:
 		ret = uart_wait_modem_status(state, arg);
-		break;
-
-	case TIOCGICOUNT:
-		ret = uart_get_count(state, uarg);
 		break;
 	}
 
···
 #endif
 	.tiocmget	= uart_tiocmget,
 	.tiocmset	= uart_tiocmset,
+	.get_icount	= uart_get_icount,
 #ifdef CONFIG_CONSOLE_POLL
 	.poll_init	= uart_poll_init,
 	.poll_get_char	= uart_poll_get_char,

drivers/usb/serial/usb-serial.c

···
 	return -EINVAL;
 }
 
+static int serial_get_icount(struct tty_struct *tty,
+				struct serial_icounter_struct *icount)
+{
+	struct usb_serial_port *port = tty->driver_data;
+
+	dbg("%s - port %d", __func__, port->number);
+
+	if (port->serial->type->get_icount)
+		return port->serial->type->get_icount(tty, icount);
+	return -EINVAL;
+}
+
 /*
  * We would be calling tty_wakeup here, but unfortunately some line
  * disciplines have an annoying habit of calling tty->write from
···
 	.chars_in_buffer =	serial_chars_in_buffer,
 	.tiocmget =		serial_tiocmget,
 	.tiocmset =		serial_tiocmset,
+	.get_icount = 		serial_get_icount,
 	.cleanup = 		serial_cleanup,
 	.install = 		serial_install,
 	.proc_fops =		&serial_proc_fops,

include/linux/tty_driver.h

···
  *	unless the tty also has a valid tty->termiox pointer.
  *
  *	Optional: Called under the termios lock
+ *
+ * int (*get_icount)(struct tty_struct *tty, struct serial_icounter *icount);
+ *
+ *	Called when the device receives a TIOCGICOUNT ioctl. Passed a kernel
+ *	structure to complete. This method is optional and will only be called
+ *	if provided (otherwise EINVAL will be returned).
  */
 
 #include <linux/fs.h>
···
 
 struct tty_struct;
 struct tty_driver;
+struct serial_icounter_struct;
 
 struct tty_operations {
 	struct tty_struct * (*lookup)(struct tty_driver *driver,
···
 			unsigned int set, unsigned int clear);
 	int (*resize)(struct tty_struct *tty, struct winsize *ws);
 	int (*set_termiox)(struct tty_struct *tty, struct termiox *tnew);
+	int (*get_icount)(struct tty_struct *tty,
+				struct serial_icounter_struct *icount);
 #ifdef CONFIG_CONSOLE_POLL
 	int (*poll_init)(struct tty_driver *driver, int line, char *options);
 	int (*poll_get_char)(struct tty_driver *driver, int line);

include/linux/usb/serial.h

···
 	int  (*tiocmget)(struct tty_struct *tty, struct file *file);
 	int  (*tiocmset)(struct tty_struct *tty, struct file *file,
 			 unsigned int set, unsigned int clear);
+	int  (*get_icount)(struct tty_struct *tty,
+			struct serial_icounter_struct *icount);
 	/* Called by the tty layer for port level work. There may or may not
 	   be an attached tty at this point */
 	void (*dtr_rts)(struct usb_serial_port *port, int on);