[PATCH v7] usb:serial:pl2303: add GPIOs interface on PL2303

[Wang YanQing <udknight@gmail.com>]

PL2303 USB Serial devices always has GPIOs, this patch add
generic gpio support interfaces for pl2303 USB Serial devices
in pl2303_type_data and pl2303_serial_private, then use them
to add GPIOs support for one type of them, PL2303HXA.

Known issue:
If gpios are in use(export to userspace through sysfs interface, etc),
then call pl2303_release(unplug usb-serial convertor, modprobe -r, etc),
will cause trouble, so we need to make sure there is no gpio user before
call pl2303_release.

Signed-off-by: Wang YanQing <udknight@gmail.com>
---
 Changes 
 v6-v7:
 1: add generic gpio support interfaces for pl2303 USB Serial devices
    in pl2303_type_data and pl2303_serial_private suggested by Andreas Mohr.
 2: drop different label names for different pl2303 instance suggested by Johan Hovold.
 3: fix missing lock corrected by Johan Hovold.
 4: use prefix pl2303hx_gpio instead pl2303_gpio, pl2303_gpio is over generic for current code,
    and now we move gpio_startup|gpio_release into type-specified data structure, so pl2303hx_gpio
    is a better prefix.
 5: make words in Kconfig a little more useful and clarified.
 6: many misc code quality enhancement suggested by Johan Hovold.

 v5-v6:
 1: fix typo error in Kconfig reported by Andreas Mohr 
 2: add const qulification to gpio_dir_mask and gpio_value_mask suggested by Andreas Mohr

 v4-v5:
 1: fix gpio_chip.lable been overwrited by template_chip. 
 2: use idr to manage minor instead of crude monotonous atomic increment. 

 v3-v4:
 1: fix missing static for gpio_dir_mask and gpio_value_mask 
 2: reduce unneeded compile macro defined suggested by gnomes@lxorguk.ukuu.org.uk 
 3: use true instead of 1 corrected by Linus Walleij
 4: ignore return value of gpiochip_remove suggested by Linus Walleij
 5: fix multi gpio_chips registered by pl2303 can't be distinguished in kernel space. 

 v2-v3:
 1: fix errors and warnings reported by Daniele Forsi checked with checkpatch.pl 
 2: fix missing GPIOLIB dependence in Kconfig 
 3: fix pl2303_gpio_get can't work 

 v1-v2:  
 1:drop gpio-pl2303.c and relation stuff 
 2:hang gpio stuff off of pl2303.c  

 drivers/usb/serial/Kconfig  |  10 +++
 drivers/usb/serial/pl2303.c | 202 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 212 insertions(+)

diff --git a/drivers/usb/serial/Kconfig b/drivers/usb/serial/Kconfig
index 3ce5c74..008ec57 100644
--- a/drivers/usb/serial/Kconfig
+++ b/drivers/usb/serial/Kconfig
@@ -516,6 +516,16 @@ config USB_SERIAL_PL2303
 	  To compile this driver as a module, choose M here: the
 	  module will be called pl2303.
 
+config USB_SERIAL_PL2303_GPIO
+	bool "USB Prolific 2303 Single Port GPIOs support"
+	depends on USB_SERIAL_PL2303 && GPIOLIB
+	---help---
+	  Say Y here if you want to use GPIOs on PL2303 USB Serial single port
+	  adapter from Prolific.
+
+	  It supports 2 dedicated GPIOs on PL2303HXA only currently.
+	  If unsure, say N.
+
 config USB_SERIAL_OTI6858
 	tristate "USB Ours Technology Inc. OTi-6858 USB To RS232 Bridge Controller"
 	help
diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index b3d5a35..edbe634 100644
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -28,6 +28,8 @@
 #include <linux/usb.h>
 #include <linux/usb/serial.h>
 #include <asm/unaligned.h>
+#include <linux/gpio.h>
+#include <linux/mutex.h>
 #include "pl2303.h"
 
 
@@ -131,6 +133,8 @@ MODULE_DEVICE_TABLE(usb, id_table);
 #define UART_OVERRUN_ERROR		0x40
 #define UART_CTS			0x80
 
+#define PL2303HX_REG_GPIO_CONTROL	0x01
+#define PL2303HX_REG_GPIO_STATE	0x81
 
 enum pl2303_type {
 	TYPE_01,	/* Type 0 and 1 (difference unknown) */
@@ -141,11 +145,15 @@ enum pl2303_type {
 struct pl2303_type_data {
 	speed_t max_baud_rate;
 	unsigned long quirks;
+	u16 ngpio;
+	int (*gpio_startup)(struct usb_serial *serial);
+	void (*gpio_release)(struct usb_serial *serial);
 };
 
 struct pl2303_serial_private {
 	const struct pl2303_type_data *type;
 	unsigned long quirks;
+	void *gpio;
 };
 
 struct pl2303_private {
@@ -156,11 +164,24 @@ struct pl2303_private {
 	u8 line_settings[7];
 };
 
+#ifdef CONFIG_USB_SERIAL_PL2303_GPIO
+static int pl2303hx_gpio_startup(struct usb_serial *serial);
+static void pl2303hx_gpio_release(struct usb_serial *serial);
+#else
+static inline int pl2303hx_gpio_startup(struct usb_serial *serial) { return 0; }
+static inline void pl2303hx_gpio_release(struct usb_serial *serial) {}
+#endif
+
 static const struct pl2303_type_data pl2303_type_data[TYPE_COUNT] = {
 	[TYPE_01] = {
 		.max_baud_rate =	1228800,
 		.quirks =		PL2303_QUIRK_LEGACY,
 	},
+	[TYPE_HX] = {
+		.ngpio = 2,
+		.gpio_startup = pl2303hx_gpio_startup,
+		.gpio_release = pl2303hx_gpio_release,
+	}
 };
 
 static int pl2303_vendor_read(struct usb_serial *serial, u16 value,
@@ -213,6 +234,176 @@ static int pl2303_probe(struct usb_serial *serial,
 	return 0;
 }
 
+#ifdef CONFIG_USB_SERIAL_PL2303_GPIO
+struct pl2303hx_gpio_data {
+	/*
+	 * 0..3: unknown (zero)
+	 * 4: gp0 output enable (1: gp0 pin is output, 0: gp0 pin is input)
+	 * 5: gp1 output enable (1: gp1 pin is output, 0: gp1 pin is input)
+	 * 6: gp0 pin value
+	 * 7: gp1 pin value
+	 */
+	u8 index;
+	struct mutex lock;
+	struct usb_serial *serial;
+	struct gpio_chip gpio_chip;
+};
+
+static inline struct pl2303hx_gpio_data *to_pl2303hx_gpio_data(struct gpio_chip *chip)
+{
+	return container_of(chip, struct pl2303hx_gpio_data, gpio_chip);
+}
+
+static u8 pl2303hx_gpio_dir_mask(unsigned offset)
+{
+	switch(offset)
+	{
+	case 0:
+		return 0x10;
+	case 1:
+		return 0x20;
+	default:
+		break;
+	};
+	return 0;
+}
+
+static u8 pl2303hx_gpio_value_mask(unsigned offset)
+{
+	switch(offset)
+	{
+	case 0:
+		return 0x40;
+	case 1:
+		return 0x80;
+	default:
+		break;
+	};
+	return 0;
+}
+
+static int pl2303hx_gpio_direction_in(struct gpio_chip *chip, unsigned offset)
+{
+	struct pl2303hx_gpio_data *gpio = to_pl2303hx_gpio_data(chip);
+	int ret;
+
+	mutex_lock(&gpio->lock);
+	gpio->index &= ~pl2303hx_gpio_dir_mask(offset);
+	ret = pl2303_vendor_write(gpio->serial, PL2303HX_REG_GPIO_CONTROL, gpio->index);
+	mutex_unlock(&gpio->lock);
+
+	return ret;
+}
+
+static int pl2303hx_gpio_direction_out(struct gpio_chip *chip,
+				unsigned offset, int value)
+{
+	struct pl2303hx_gpio_data *gpio = to_pl2303hx_gpio_data(chip);
+	int ret;
+
+	mutex_lock(&gpio->lock);
+	gpio->index |= pl2303hx_gpio_dir_mask(offset);
+	if (value)
+		gpio->index |= pl2303hx_gpio_value_mask(offset);
+	else
+		gpio->index &= ~pl2303hx_gpio_value_mask(offset);
+
+	ret = pl2303_vendor_write(gpio->serial, PL2303HX_REG_GPIO_CONTROL, gpio->index);
+	mutex_unlock(&gpio->lock);
+
+	return ret;
+}
+
+static void pl2303hx_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
+{
+	struct pl2303hx_gpio_data *gpio = to_pl2303hx_gpio_data(chip);
+
+	mutex_lock(&gpio->lock);
+	if (value)
+		gpio->index |= pl2303hx_gpio_value_mask(offset);
+	else
+		gpio->index &= ~pl2303hx_gpio_value_mask(offset);
+
+	pl2303_vendor_write(gpio->serial, PL2303HX_REG_GPIO_CONTROL, gpio->index);
+	mutex_unlock(&gpio->lock);
+}
+
+static int pl2303hx_gpio_get(struct gpio_chip *chip, unsigned offset)
+{
+	struct pl2303hx_gpio_data *gpio = to_pl2303hx_gpio_data(chip);
+	unsigned char *buf;
+	int value = 0;
+
+	buf = kmalloc(1, GFP_KERNEL);
+	if (!buf) {
+		return -ENOMEM;
+	}
+
+	mutex_lock(&gpio->lock);
+	if (pl2303_vendor_read(gpio->serial, PL2303HX_REG_GPIO_STATE, buf)) {
+		mutex_unlock(&gpio->lock);
+		return -EIO;
+	}
+
+	value = buf[0] & pl2303hx_gpio_value_mask(offset);
+	mutex_unlock(&gpio->lock);
+	kfree(buf);
+
+	return value;
+}
+
+static int pl2303hx_gpio_startup(struct usb_serial *serial)
+{
+	struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
+	struct pl2303hx_gpio_data *gpio;
+	int ret;
+
+	gpio = kzalloc(sizeof(struct pl2303hx_gpio_data), GFP_KERNEL);
+	if (!gpio) {
+		dev_err(&serial->interface->dev,
+			"Failed to allocate pl2303_gpio_data\n");
+		return -ENOMEM;
+	}
+
+	gpio->index = 0x00;
+	gpio->serial = serial;
+	mutex_init(&gpio->lock);
+
+	gpio->gpio_chip.label = "pl2303";
+	gpio->gpio_chip.owner = THIS_MODULE;
+	gpio->gpio_chip.direction_input = pl2303hx_gpio_direction_in;
+	gpio->gpio_chip.get = pl2303hx_gpio_get;
+	gpio->gpio_chip.direction_output = pl2303hx_gpio_direction_out;
+	gpio->gpio_chip.set = pl2303hx_gpio_set;
+	gpio->gpio_chip.can_sleep  = true;
+	gpio->gpio_chip.ngpio = spriv->type->ngpio;
+	gpio->gpio_chip.base = -1;
+	gpio->gpio_chip.dev = &serial->interface->dev;
+
+	/* initialize GPIOs, input mode as default */
+	pl2303_vendor_write(gpio->serial, PL2303HX_REG_GPIO_CONTROL, gpio->index);
+
+	ret = gpiochip_add(&gpio->gpio_chip);
+	if (ret < 0) {
+		dev_err(&serial->interface->dev,
+			"Could not register gpiochip, %d\n", ret);
+		kfree(gpio);
+		return ret;
+	}
+	spriv->gpio = gpio;
+	return 0;
+}
+
+static void pl2303hx_gpio_release(struct usb_serial *serial)
+{
+	struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
+	struct pl2303hx_gpio_data *gpio = (struct pl2303hx_gpio_data *)spriv->gpio;
+
+	gpiochip_remove(&gpio->gpio_chip);
+	kfree(gpio);
+}
+#endif
+
 static int pl2303_startup(struct usb_serial *serial)
 {
 	struct pl2303_serial_private *spriv;
@@ -262,6 +453,15 @@ static int pl2303_startup(struct usb_serial *serial)
 
 	kfree(buf);
 
+	if (spriv->type->ngpio > 0) {
+		int ret;
+
+		ret = spriv->type->gpio_startup(serial);
+		if (ret) {
+			kfree(spriv);
+			return ret;
+		}
+	}
 	return 0;
 }
 
@@ -269,6 +469,8 @@ static void pl2303_release(struct usb_serial *serial)
 {
 	struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
 
+	if (spriv->type->ngpio > 0)
+		spriv->type->gpio_release(serial);
 	kfree(spriv);
 }
 
-- 
1.8.5.5.dirty