USb: Break support for WinChipHead CH341 340 USB->Serial "chip"

Here is a patch to the ch341 driver which adds serial break support.
Signed-off-by: Tim Small <tim@seoss.co.uk>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/ch341.c

@@ -56,6 +56,18 @@
 #define CH341_BAUDBASE_FACTOR 1532620800
 #define CH341_BAUDBASE_DIVMAX 3
 
+/* Break support - the information used to implement this was gleaned from
+ * the Net/FreeBSD uchcom.c driver by Takanori Watanabe.  Domo arigato.
+ */
+
+#define CH341_REQ_WRITE_REG    0x9A
+#define CH341_REQ_READ_REG     0x95
+#define CH341_REG_BREAK1       0x05
+#define CH341_REG_BREAK2       0x18
+#define CH341_NBREAK_BITS_REG1 0x01
+#define CH341_NBREAK_BITS_REG2 0x40
+
+
 static int debug;
 
 static struct usb_device_id id_table [] = {
@@ -373,6 +385,45 @@ static void ch341_set_termios(struct tty_struct *tty,
 	 */
 }
 
+static void ch341_break_ctl(struct tty_struct *tty, int break_state)
+{
+	const uint16_t ch341_break_reg =
+		CH341_REG_BREAK1 | ((uint16_t) CH341_REG_BREAK2 << 8);
+	struct usb_serial_port *port = tty->driver_data;
+	int r;
+	uint16_t reg_contents;
+	uint8_t break_reg[2];
+
+	dbg("%s()", __func__);
+
+	r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
+			ch341_break_reg, 0, break_reg, sizeof(break_reg));
+	if (r < 0) {
+		printk(KERN_WARNING "%s: USB control read error whilst getting"
+				" break register contents.\n", __FILE__);
+		return;
+	}
+	dbg("%s - initial ch341 break register contents - reg1: %x, reg2: %x",
+			__func__, break_reg[0], break_reg[1]);
+	if (break_state != 0) {
+		dbg("%s - Enter break state requested", __func__);
+		break_reg[0] &= ~CH341_NBREAK_BITS_REG1;
+		break_reg[1] &= ~CH341_NBREAK_BITS_REG2;
+	} else {
+		dbg("%s - Leave break state requested", __func__);
+		break_reg[0] |= CH341_NBREAK_BITS_REG1;
+		break_reg[1] |= CH341_NBREAK_BITS_REG2;
+	}
+	dbg("%s - New ch341 break register contents - reg1: %x, reg2: %x",
+			__func__, break_reg[0], break_reg[1]);
+	reg_contents = (uint16_t)break_reg[0] | ((uint16_t)break_reg[1] << 8);
+	r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
+			ch341_break_reg, reg_contents);
+	if (r < 0)
+		printk(KERN_WARNING "%s: USB control write error whilst setting"
+				" break register contents.\n", __FILE__);
+}
+
 static int ch341_tiocmset(struct tty_struct *tty, struct file *file,
 			  unsigned int set, unsigned int clear)
 {
@@ -576,6 +627,7 @@ static struct usb_serial_driver ch341_device = {
 	.close             = ch341_close,
 	.ioctl             = ch341_ioctl,
 	.set_termios       = ch341_set_termios,
+	.break_ctl         = ch341_break_ctl,
 	.tiocmget          = ch341_tiocmget,
 	.tiocmset          = ch341_tiocmset,
 	.read_int_callback = ch341_read_int_callback,