[PATCH v2 08/15] HID: ft260: uart: add modem pins control via ioctl

[Michael Zaidman <michael.zaidman@gmail.com>]

Add TIOCMGET/TIOCMSET (and thus TIOCMBIS/TIOCMBIC) support so userspace
can drive DTR/RTS when the modem pins are in GPIO mode. This enables
programming an ESP32 over the FT260 with esptool, which resets the chip
via those lines.

Also key GPIO sysfs registration off chip_mode rather than USB interface
number 0, and include DCD/RI in UART mode 3/4 GPIO sets so the modem
mask matches the pins esptool needs.

The RTS, CTS, DTR and DSR pins are active-low, so TIOCMGET inverts the
sense of those four lines and TIOCMSET drives 0 to assert them. DCD and
RI are not inverted. Rio Liu found and fixed the polarity.

Keep the errno from ft260_get_interface_type() so a failed status read
does not probe-succeed after teardown. Return -EINVAL when the modem
pins are not in GPIO mode, propagate gpio_get_all() errors from
TIOCMGET, and copy the GPIO shadow under the port lock for TIOCMSET
(reported by Sashiko).

Co-developed-by: Rio Liu <rio@r26.me>
Signed-off-by: Rio Liu <rio@r26.me>
Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>

---
v2: polarity fix folded in (Rio Liu); preserve get_interface_type
errno; tiocmget/tiocmset error paths and locked shadow copy (reported
by Sashiko).
---
 drivers/hid/hid-ft260.c | 150 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 131 insertions(+), 19 deletions(-)

diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c
index 4b0b55c98f90..4106066b6a89 100644
--- a/drivers/hid/hid-ft260.c
+++ b/drivers/hid/hid-ft260.c
@@ -16,6 +16,7 @@
 #include <linux/serial.h>
 #include <linux/serial_core.h>
 #include <linux/kfifo.h>
+#include <linux/tty.h>
 #include <linux/tty_flip.h>
 #include <linux/math.h>
 #include <linux/minmax.h>
@@ -183,7 +184,7 @@ enum {
 	FT260_GPIO_DIR_OUTPUT		= 0x01,
 };
 
-/* GPIO offsets */
+/* GPIO bit masks */
 #define FT260_GPIO_0		BIT(0)
 #define FT260_GPIO_1		BIT(1)
 #define FT260_GPIO_2		BIT(2)
@@ -213,7 +214,8 @@ enum {
 #define FT260_GPIO_UART_MODE_1_SET	FT260_GPIO_UART_DTR_DSR
 #define FT260_GPIO_UART_MODE_2_SET	FT260_GPIO_UART_RTS_CTS
 #define FT260_GPIO_UART_MODE_3_SET	(FT260_GPIO_UART_RTS_CTS | \
-					 FT260_GPIO_UART_DTR_DSR)
+					 FT260_GPIO_UART_DTR_DSR | \
+					 FT260_GPIO_UART_DCD_RI)
 #define FT260_GPIO_UART_MODE_4_SET	FT260_GPIO_UART_MODE_3_SET
 #define FT260_GPIO_UART_DEFAULT		FT260_GPIO_UART_MODE_0_SET
 #define FT260_GPIO_UART_MODE_1_CLR	(FT260_GPIO_UART_RX_TX | \
@@ -223,6 +225,16 @@ enum {
 #define FT260_GPIO_UART_MODE_3_CLR	FT260_GPIO_UART_RX_TX
 #define FT260_GPIO_UART_MODES		5
 
+/* UART modem control GPIO offsets */
+enum {
+	FT260_GPIO_UART_DCD		= (4),
+	FT260_GPIO_UART_RI		= (5),
+	FT260_GPIO_UART_RTS		= (7),
+	FT260_GPIO_UART_CTS		= (10),
+	FT260_GPIO_UART_DTR		= (11),
+	FT260_GPIO_UART_DSR		= (13),
+};
+
 #define FT260_SET_REQUEST_VALUE(report_id) ((FT260_FEATURE << 8) | (report_id))
 
 /* Feature In reports */
@@ -449,6 +461,7 @@ MODULE_DEVICE_TABLE(hid, ft260_devices);
 struct ft260_device {
 	struct i2c_adapter adap;
 	struct hid_device *hdev;
+	int chip_mode;
 	int iface_type;
 	int iface_id;
 	struct list_head device_list;
@@ -1106,7 +1119,27 @@ static void ft260_gpio_en_update(struct hid_device *hdev, u8 req, u8 value)
 	else
 		ft260_gpio_en_clr(dev, bitmap);
 exit:
-	hid_info(hdev, "enabled GPIOs: %04x\n", dev->gpio_en);
+	hid_info(hdev, "enabled GPIOs: %04x, bitmap %04x\n",
+		 dev->gpio_en, bitmap);
+}
+
+static void ft260_gpio_output_cfg(struct ft260_gpio_state *gpio,
+				  u32 offset, int value)
+{
+	if (offset < FT260_GPIO_0_5_COUNT) {
+		gpio->dirs |= BIT(offset);
+		if (value)
+			gpio->vals |= !!value << offset;
+		else
+			gpio->vals &= ~BIT(offset);
+	} else {
+		offset = offset - FT260_GPIO_0_5_COUNT;
+		gpio->ex_dirs |= BIT(offset);
+		if (value)
+			gpio->ex_vals |= !!value << offset;
+		else
+			gpio->ex_vals &= ~BIT(offset);
+	}
 }
 
 static int ft260_gpio_set(struct gpio_chip *gc, u32 offset, int value)
@@ -1155,7 +1188,7 @@ static int ft260_gpio_set(struct gpio_chip *gc, u32 offset, int value)
 			rep.gpio.ex_vals &= ~BIT(offset);
 	}
 
-	ft260_dbg("dirs %#02x vals %#02x ex_dir %#02x ex_vals %#02x\n",
+	ft260_dbg("dirs %#02x vals %#02x ex_dirs %#02x ex_vals %#02x\n",
 		  rep.gpio.dirs, rep.gpio.vals,
 		  rep.gpio.ex_dirs, rep.gpio.ex_vals);
 
@@ -1307,8 +1340,6 @@ static int ft260_gpio_init(struct ft260_device *dev,
 	char prefix[] = "ft260_";
 	u8 mode = cfg->chip_mode;
 
-	hid_info(hdev, "initialize gpio chip\n");
-
 	dev->gpio_uart_mode[0] = (u16)FT260_GPIO_UART_MODE_0_SET;
 	dev->gpio_uart_mode[1] = (u16)FT260_GPIO_UART_MODE_1_SET;
 	dev->gpio_uart_mode[2] = (u16)FT260_GPIO_UART_MODE_2_SET;
@@ -1352,7 +1383,6 @@ static int ft260_gpio_init(struct ft260_device *dev,
 		goto exit;
 	}
 	snprintf(label, label_sz, "%s%s", prefix, dev_name(&hdev->dev));
-	hid_info(hdev, "initialize gpio chip on %s\n", label);
 
 	dev->gc->label			= label;
 	dev->gc->direction_input	= ft260_gpio_direction_input;
@@ -1423,6 +1453,7 @@ static int ft260_get_interface_type(struct ft260_device *dev,
 	ft260_dbg("wakeup_int: 0x%02x\n", cfg->enable_wakeup_int);
 
 	dev->power_saving_en = cfg->power_saving_en;
+	dev->chip_mode = cfg->chip_mode;
 
 	switch (cfg->chip_mode) {
 	case FT260_MODE_ALL:
@@ -1440,7 +1471,6 @@ static int ft260_get_interface_type(struct ft260_device *dev,
 		break;
 	}
 
-	dev->iface_type = ret;
 	return ret;
 }
 
@@ -1941,6 +1971,80 @@ static void ft260_uart_set_termios(struct tty_struct *tty,
 	ft260_uart_change_speed(port, &tty->termios, NULL);
 }
 
+static int ft260_uart_tiocmget(struct tty_struct *tty)
+{
+	struct ft260_device *port = tty->driver_data;
+	int gpios;
+
+	/*
+	 * The modem lines control via ioctl is allowed only
+	 * when the related pins are in the gpio mode.
+	 */
+	int mask = FT260_GPIO_UART_MODE_4_SET;
+
+	if ((port->gpio_en & mask) != mask) {
+		ft260_dbg("Illegal gpio config %#02x != mask %#04x\n",
+			  port->gpio_en, mask);
+		return -EINVAL;
+	}
+
+	gpios = ft260_gpio_get_all(port->gc, FT260_GPIO_VALUE);
+	if (gpios < 0)
+		return gpios;
+
+	return ((!(gpios & FT260_GPIO_B) ? TIOCM_RTS : 0) |
+		(!(gpios & FT260_GPIO_E) ? TIOCM_CTS : 0) |
+		(!(gpios & FT260_GPIO_F) ? TIOCM_DTR : 0) |
+		(!(gpios & FT260_GPIO_H) ? TIOCM_DSR : 0) |
+		((gpios & FT260_GPIO_4) ? TIOCM_CAR : 0) |
+		((gpios & FT260_GPIO_5) ? TIOCM_RNG : 0));
+}
+
+static int ft260_uart_tiocmset(struct tty_struct *tty,
+			       unsigned int set, unsigned int clear)
+{
+	int ret;
+	struct ft260_device *port = tty->driver_data;
+	struct ft260_gpio_write_request_report rep;
+	struct hid_device *hdev = port->hdev;
+	int mask = FT260_GPIO_UART_MODE_4_SET;
+
+	if ((port->gpio_en & mask) != mask) {
+		ft260_dbg("Illegal gpio config %#02x != mask %#04x\n",
+			  port->gpio_en, mask);
+		return -EINVAL;
+	}
+	rep.report = FT260_GPIO;
+
+	mutex_lock(&port->lock);
+	rep.gpio = port->gpio;
+
+	if (set & TIOCM_RTS)
+		ft260_gpio_output_cfg(&rep.gpio, FT260_GPIO_UART_RTS, 0);
+	if (set & TIOCM_DTR)
+		ft260_gpio_output_cfg(&rep.gpio, FT260_GPIO_UART_DTR, 0);
+	if (clear & TIOCM_RTS)
+		ft260_gpio_output_cfg(&rep.gpio, FT260_GPIO_UART_RTS, 1);
+	if (clear & TIOCM_DTR)
+		ft260_gpio_output_cfg(&rep.gpio, FT260_GPIO_UART_DTR, 1);
+
+	ft260_dbg("dirs %#02x vals %#02x ex_dirs %#02x ex_vals %#02x\n",
+		  rep.gpio.dirs, rep.gpio.vals,
+		  rep.gpio.ex_dirs, rep.gpio.ex_vals);
+
+	ret = ft260_hid_feature_report_set(hdev, (u8 *)&rep, sizeof(rep));
+	if (unlikely(ret < 0)) {
+		hid_err(hdev, "%s: cannot set GPIO: %d\n", __func__, ret);
+		mutex_unlock(&port->lock);
+		return -EIO;
+	}
+
+	port->gpio = rep.gpio;
+	mutex_unlock(&port->lock);
+
+	return 0;
+}
+
 static int ft260_uart_install(struct tty_driver *driver, struct tty_struct *tty)
 {
 	int idx = tty->index;
@@ -2021,6 +2125,8 @@ static const struct tty_operations ft260_uart_ops = {
 	.write_room		= ft260_uart_write_room,
 	.chars_in_buffer	= ft260_uart_chars_in_buffer,
 	.set_termios		= ft260_uart_set_termios,
+	.tiocmget		= ft260_uart_tiocmget,
+	.tiocmset		= ft260_uart_tiocmset,
 	.hangup			= ft260_uart_hangup,
 	.install		= ft260_uart_install,
 	.cleanup		= ft260_uart_cleanup,
@@ -2164,14 +2270,16 @@ static int ft260_i2c_probe(struct ft260_device *dev,
 		return ret;
 	}
 
-	ret = ft260_gpio_init(dev, cfg);
-	if (ret)
-		goto err_i2c_free;
+	if (cfg->chip_mode == FT260_MODE_I2C) {
+		ret = ft260_gpio_init(dev, cfg);
+		if (ret)
+			goto err_i2c_free;
 
-	ret = sysfs_create_group(&hdev->dev.kobj, &ft260_attr_group);
-	if (ret < 0) {
-		hid_err(hdev, "failed to create sysfs attrs\n");
-		goto err_i2c_free;
+		ret = sysfs_create_group(&hdev->dev.kobj, &ft260_attr_group);
+		if (ret < 0) {
+			hid_err(hdev, "failed to create sysfs attrs\n");
+			goto err_i2c_free;
+		}
 	}
 
 	return 0;
@@ -2232,7 +2340,8 @@ static int ft260_uart_probe(struct ft260_device *dev,
 
 	cfg->uart_mode = FT260_UART_CFG_FLOW_CTRL_NONE;
 
-	if (dev->iface_id == 0) {
+	if (dev->chip_mode & FT260_MODE_UART ||
+	    dev->chip_mode == FT260_MODE_ALL) {
 		ret = ft260_gpio_init(dev, cfg);
 		if (ret)
 			goto err_hid_report;
@@ -2311,8 +2420,9 @@ static int ft260_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	ret = ft260_get_interface_type(dev, &cfg);
 	if (ret <= FT260_IFACE_NONE)
 		goto err_hid_close;
+	dev->iface_type = ret;
 
-	if (ret == FT260_IFACE_I2C) {
+	if (dev->iface_type == FT260_IFACE_I2C) {
 		ret = ft260_i2c_probe(dev, &cfg);
 		if (ret)
 			goto err_hid_close;
@@ -2353,10 +2463,12 @@ static void ft260_remove(struct hid_device *hdev)
 		tty_port_unregister_device(&dev->port, ft260_tty_driver,
 					   dev->index);
 		ft260_uart_port_remove(dev);
-		if (dev->iface_id == 0)
+		if (dev->chip_mode & FT260_MODE_UART ||
+		    dev->chip_mode == FT260_MODE_ALL)
 			sysfs_remove_group(&hdev->dev.kobj, &ft260_attr_group);
 	} else {
-		sysfs_remove_group(&hdev->dev.kobj, &ft260_attr_group);
+		if (dev->chip_mode == FT260_MODE_I2C)
+			sysfs_remove_group(&hdev->dev.kobj, &ft260_attr_group);
 		i2c_del_adapter(&dev->adap);
 	}
 
-- 
2.43.0