linux-kernel - [PATCH v3] USB: serial: xr: Add TIOCGRS485 and TIOCSRS485 ioctls

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Date:   Tue, 14 Mar 2023 09:00:01 +0200
From:   Jarkko Sonninen <kasper@....fi>
To:     Jarkko Sonninen <kasper@....fi>
Cc:     Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3] USB: serial: xr: Add TIOCGRS485 and TIOCSRS485 ioctls

Add support for RS-485 in Exar USB adapters.
RS-485 mode is controlled by TIOCGRS485 and TIOCSRS485 ioctls.
Gpio mode register is set to enable RS-485.

Signed-off-by: Jarkko Sonninen <kasper@....fi>
---

In this version only rs485.flags are stored to state.
There is no locking as only one bit of the flags is used.
ioctl returns -ENOIOCTLCMD as the actual error handling is in tty code.

 drivers/usb/serial/xr_serial.c | 62 +++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/xr_serial.c b/drivers/usb/serial/xr_serial.c
index fdb0aae546c3..7b542ccb6596 100644
--- a/drivers/usb/serial/xr_serial.c
+++ b/drivers/usb/serial/xr_serial.c
@@ -93,6 +93,7 @@ struct xr_txrx_clk_mask {
 #define XR_GPIO_MODE_SEL_DTR_DSR	0x2
 #define XR_GPIO_MODE_SEL_RS485		0x3
 #define XR_GPIO_MODE_SEL_RS485_ADDR	0x4
+#define XR_GPIO_MODE_RS485_TX_H		0x8
 #define XR_GPIO_MODE_TX_TOGGLE		0x100
 #define XR_GPIO_MODE_RX_TOGGLE		0x200
 
@@ -237,6 +238,7 @@ static const struct xr_type xr_types[] = {
 struct xr_data {
 	const struct xr_type *type;
 	u8 channel;			/* zero-based index or interface number */
+	u32 rs485_flags;
 };
 
 static int xr_set_reg(struct usb_serial_port *port, u8 channel, u16 reg, u16 val)
@@ -645,9 +647,13 @@ static void xr_set_flow_mode(struct tty_struct *tty,
 	/* Set GPIO mode for controlling the pins manually by default. */
 	gpio_mode &= ~XR_GPIO_MODE_SEL_MASK;
 
+	if (data->rs485_flags & SER_RS485_ENABLED)
+		gpio_mode |= XR_GPIO_MODE_SEL_RS485 | XR_GPIO_MODE_RS485_TX_H;
+	else if (C_CRTSCTS(tty) && C_BAUD(tty) != B0)
+		gpio_mode |= XR_GPIO_MODE_SEL_RTS_CTS;
+
 	if (C_CRTSCTS(tty) && C_BAUD(tty) != B0) {
 		dev_dbg(&port->dev, "Enabling hardware flow ctrl\n");
-		gpio_mode |= XR_GPIO_MODE_SEL_RTS_CTS;
 		flow = XR_UART_FLOW_MODE_HW;
 	} else if (I_IXON(tty)) {
 		u8 start_char = START_CHAR(tty);
@@ -827,6 +833,59 @@ static void xr_set_termios(struct tty_struct *tty,
 	xr_set_flow_mode(tty, port, old_termios);
 }
 
+static int xr_get_rs485_config(struct tty_struct *tty,
+			 unsigned int __user *argp)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct xr_data *data = usb_get_serial_port_data(port);
+	struct serial_rs485 rs485;
+
+	dev_dbg(tty->dev, "Flags %02x\n", data->rs485_flags);
+	memset(&rs485, 0, sizeof(rs485));
+	rs485.flags = data->rs485_flags;
+	if (copy_to_user(argp, &rs485, sizeof(rs485)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int xr_set_rs485_config(struct tty_struct *tty,
+			 unsigned long __user *argp)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct xr_data *data = usb_get_serial_port_data(port);
+	struct serial_rs485 rs485;
+
+	if (copy_from_user(&rs485, argp, sizeof(rs485)))
+		return -EFAULT;
+
+	dev_dbg(tty->dev, "Flags %02x\n", rs485.flags);
+	data->rs485_flags = rs485.flags & SER_RS485_ENABLED;
+	xr_set_flow_mode(tty, port, (const struct ktermios *)0);
+
+	// Only the enable flag is implemented
+	memset(&rs485, 0, sizeof(rs485));
+	rs485.flags = data->rs485_flags;
+	if (copy_to_user(argp, &rs485, sizeof(rs485)))
+		return -EFAULT;
+
+	return 0;
+}
+
+
+static int xr_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
+{
+	void __user *argp = (void __user *)arg;
+
+	switch (cmd) {
+	case TIOCGRS485:
+		return xr_get_rs485_config(tty, argp);
+	case TIOCSRS485:
+		return xr_set_rs485_config(tty, argp);
+	}
+	return -ENOIOCTLCMD;
+}
+
 static int xr_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
 	int ret;
@@ -1010,6 +1069,7 @@ static struct usb_serial_driver xr_device = {
 	.set_termios		= xr_set_termios,
 	.tiocmget		= xr_tiocmget,
 	.tiocmset		= xr_tiocmset,
+	.ioctl			= xr_ioctl,
 	.dtr_rts		= xr_dtr_rts
 };
 
-- 
2.34.1