/* MCP23S08 SPI/I2C GPIO driver */

#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/i2c.h>
#include <linux/spi/spi.h>
#include <linux/spi/mcp23s08.h>
#include <linux/slab.h>
#include <asm/byteorder.h>
#include <linux/interrupt.h>
#include <linux/of_device.h>
#include <linux/regmap.h>
#include <linux/pinctrl/pinctrl.h>
#include <linux/pinctrl/pinconf.h>
#include <linux/pinctrl/pinconf-generic.h>

/*
 * MCP types supported by driver
 */
#define MCP_TYPE_S08	0
#define MCP_TYPE_S17	1
#define MCP_TYPE_008	2
#define MCP_TYPE_017	3
#define MCP_TYPE_S18    4

#define MCP_MAX_DEV_PER_CS	8

/* Registers are all 8 bits wide.
 *
 * The mcp23s17 has twice as many bits, and can be configured to work
 * with either 16 bit registers or with two adjacent 8 bit banks.
 */
#define MCP_IODIR	0x00		/* init/reset:  all ones */
#define MCP_IPOL	0x01
#define MCP_GPINTEN	0x02
#define MCP_DEFVAL	0x03
#define MCP_INTCON	0x04
#define MCP_IOCON	0x05
#	define IOCON_MIRROR	(1 << 6)
#	define IOCON_SEQOP	(1 << 5)
#	define IOCON_HAEN	(1 << 3)
#	define IOCON_ODR	(1 << 2)
#	define IOCON_INTPOL	(1 << 1)
#	define IOCON_INTCC	(1)
#define MCP_GPPU	0x06
#define MCP_INTF	0x07
#define MCP_INTCAP	0x08
#define MCP_GPIO	0x09
#define MCP_OLAT	0x0a

struct mcp23s08;

struct mcp23s08 {
	u8			addr;
	bool			irq_active_high;
	bool			reg_shift;

	u16			irq_rise;
	u16			irq_fall;
	int			irq;
	bool			irq_controller;
	int			cached_gpio;
	/* lock protects regmap access with bypass/cache flags */
	struct mutex		lock;

	struct gpio_chip	chip;

	struct regmap		*regmap;
	struct device		*dev;

	struct pinctrl_dev	*pctldev;
	struct pinctrl_desc	pinctrl_desc;
};

static const struct reg_default mcp23x08_defaults[] = {
	{.reg = MCP_IODIR,		.def = 0xff},
	{.reg = MCP_IPOL,		.def = 0x00},
	{.reg = MCP_GPINTEN,		.def = 0x00},
	{.reg = MCP_DEFVAL,		.def = 0x00},
	{.reg = MCP_INTCON,		.def = 0x00},
	{.reg = MCP_IOCON,		.def = 0x00},
	{.reg = MCP_GPPU,		.def = 0x00},
	{.reg = MCP_OLAT,		.def = 0x00},
};

static const struct regmap_range mcp23x08_volatile_range = {
	.range_min = MCP_INTF,
	.range_max = MCP_GPIO,
};

static const struct regmap_access_table mcp23x08_volatile_table = {
	.yes_ranges = &mcp23x08_volatile_range,
	.n_yes_ranges = 1,
};

static const struct regmap_range mcp23x08_precious_range = {
	.range_min = MCP_GPIO,
	.range_max = MCP_GPIO,
};

static const struct regmap_access_table mcp23x08_precious_table = {
	.yes_ranges = &mcp23x08_precious_range,
	.n_yes_ranges = 1,
};

static const struct regmap_config mcp23x08_regmap = {
	.reg_bits = 8,
	.val_bits = 8,

	.reg_stride = 1,
	.volatile_table = &mcp23x08_volatile_table,
	.precious_table = &mcp23x08_precious_table,
	.reg_defaults = mcp23x08_defaults,
	.num_reg_defaults = ARRAY_SIZE(mcp23x08_defaults),
	.cache_type = REGCACHE_FLAT,
	.max_register = MCP_OLAT,
};

static const struct reg_default mcp23x16_defaults[] = {
	{.reg = MCP_IODIR << 1,		.def = 0xffff},
	{.reg = MCP_IPOL << 1,		.def = 0x0000},
	{.reg = MCP_GPINTEN << 1,	.def = 0x0000},
	{.reg = MCP_DEFVAL << 1,	.def = 0x0000},
	{.reg = MCP_INTCON << 1,	.def = 0x0000},
	{.reg = MCP_IOCON << 1,		.def = 0x0000},
	{.reg = MCP_GPPU << 1,		.def = 0x0000},
	{.reg = MCP_OLAT << 1,		.def = 0x0000},
};

static const struct regmap_range mcp23x16_volatile_range = {
	.range_min = MCP_INTF << 1,
	.range_max = MCP_GPIO << 1,
};

static const struct regmap_access_table mcp23x16_volatile_table = {
	.yes_ranges = &mcp23x16_volatile_range,
	.n_yes_ranges = 1,
};

static const struct regmap_range mcp23x16_precious_range = {
	.range_min = MCP_GPIO << 1,
	.range_max = MCP_GPIO << 1,
};

static const struct regmap_access_table mcp23x16_precious_table = {
	.yes_ranges = &mcp23x16_precious_range,
	.n_yes_ranges = 1,
};

static const struct regmap_config mcp23x17_regmap = {
	.reg_bits = 8,
	.val_bits = 16,

	.reg_stride = 2,
	.max_register = MCP_OLAT << 1,
	.volatile_table = &mcp23x16_volatile_table,
	.precious_table = &mcp23x16_precious_table,
	.reg_defaults = mcp23x16_defaults,
	.num_reg_defaults = ARRAY_SIZE(mcp23x16_defaults),
	.cache_type = REGCACHE_FLAT,
	.val_format_endian = REGMAP_ENDIAN_LITTLE,
};

static int mcp_read(struct mcp23s08 *mcp, unsigned int reg, unsigned int *val)
{
	return regmap_read(mcp->regmap, reg << mcp->reg_shift, val);
}

static int mcp_write(struct mcp23s08 *mcp, unsigned int reg, unsigned int val)
{
	return regmap_write(mcp->regmap, reg << mcp->reg_shift, val);
}

static int mcp_set_mask(struct mcp23s08 *mcp, unsigned int reg,
		       unsigned int mask, bool enabled)
{
	u16 val  = enabled ? 0xffff : 0x0000;
	return regmap_update_bits(mcp->regmap, reg << mcp->reg_shift,
				  mask, val);
}

static int mcp_set_bit(struct mcp23s08 *mcp, unsigned int reg,
		       unsigned int pin, bool enabled)
{
	u16 mask = BIT(pin);
	return mcp_set_mask(mcp, reg, mask, enabled);
}

static const struct pinctrl_pin_desc mcp23x08_pins[] = {
	PINCTRL_PIN(0, "gpio0"),
	PINCTRL_PIN(1, "gpio1"),
	PINCTRL_PIN(2, "gpio2"),
	PINCTRL_PIN(3, "gpio3"),
	PINCTRL_PIN(4, "gpio4"),
	PINCTRL_PIN(5, "gpio5"),
	PINCTRL_PIN(6, "gpio6"),
	PINCTRL_PIN(7, "gpio7"),
};

static const struct pinctrl_pin_desc mcp23x17_pins[] = {
	PINCTRL_PIN(0, "gpio0"),
	PINCTRL_PIN(1, "gpio1"),
	PINCTRL_PIN(2, "gpio2"),
	PINCTRL_PIN(3, "gpio3"),
	PINCTRL_PIN(4, "gpio4"),
	PINCTRL_PIN(5, "gpio5"),
	PINCTRL_PIN(6, "gpio6"),
	PINCTRL_PIN(7, "gpio7"),
	PINCTRL_PIN(8, "gpio8"),
	PINCTRL_PIN(9, "gpio9"),
	PINCTRL_PIN(10, "gpio10"),
	PINCTRL_PIN(11, "gpio11"),
	PINCTRL_PIN(12, "gpio12"),
	PINCTRL_PIN(13, "gpio13"),
	PINCTRL_PIN(14, "gpio14"),
	PINCTRL_PIN(15, "gpio15"),
};

static int mcp_pinctrl_get_groups_count(struct pinctrl_dev *pctldev)
{
	return 0;
}

static const char *mcp_pinctrl_get_group_name(struct pinctrl_dev *pctldev,
						unsigned int group)
{
	return NULL;
}

static int mcp_pinctrl_get_group_pins(struct pinctrl_dev *pctldev,
					unsigned int group,
					const unsigned int **pins,
					unsigned int *num_pins)
{
	return -ENOTSUPP;
}

static const struct pinctrl_ops mcp_pinctrl_ops = {
	.get_groups_count = mcp_pinctrl_get_groups_count,
	.get_group_name = mcp_pinctrl_get_group_name,
	.get_group_pins = mcp_pinctrl_get_group_pins,
#ifdef CONFIG_OF
	.dt_node_to_map = pinconf_generic_dt_node_to_map_pin,
	.dt_free_map = pinconf_generic_dt_free_map,
#endif
};

static int mcp_pinconf_get(struct pinctrl_dev *pctldev, unsigned int pin,
			      unsigned long *config)
{
	struct mcp23s08 *mcp = pinctrl_dev_get_drvdata(pctldev);
	enum pin_config_param param = pinconf_to_config_param(*config);
	unsigned int data, status;
	int ret;

	switch (param) {
	case PIN_CONFIG_BIAS_PULL_UP:
		ret = mcp_read(mcp, MCP_GPPU, &data);
		if (ret < 0)
			return ret;
		status = (data & BIT(pin)) ? 1 : 0;
		break;
	default:
		dev_err(mcp->dev, "Invalid config param %04x\n", param);
		return -ENOTSUPP;
	}

	*config = 0;

	return status ? 0 : -EINVAL;
}

static int mcp_pinconf_set(struct pinctrl_dev *pctldev, unsigned int pin,
			      unsigned long *configs, unsigned int num_configs)
{
	struct mcp23s08 *mcp = pinctrl_dev_get_drvdata(pctldev);
	enum pin_config_param param;
	u32 arg, mask;
	u16 val;
	int ret = 0;
	int i;

	for (i = 0; i < num_configs; i++) {
		param = pinconf_to_config_param(configs[i]);
		arg = pinconf_to_config_argument(configs[i]);

		switch (param) {
		case PIN_CONFIG_BIAS_PULL_UP:
			val = arg ? 0xFFFF : 0x0000;
			mask = BIT(pin);
			ret = mcp_set_bit(mcp, MCP_GPPU, pin, arg);
			break;
		default:
			dev_err(mcp->dev, "Invalid config param %04x\n", param);
			return -ENOTSUPP;
		}
	}

	return ret;
}

static const struct pinconf_ops mcp_pinconf_ops = {
	.pin_config_get = mcp_pinconf_get,
	.pin_config_set = mcp_pinconf_set,
	.is_generic = true,
};

/*----------------------------------------------------------------------*/

#ifdef CONFIG_SPI_MASTER

static int mcp23sxx_spi_write(void *context, const void *data, size_t count)
{
	struct mcp23s08 *mcp = context;
	struct spi_device *spi = to_spi_device(mcp->dev);
	struct spi_message m;
	struct spi_transfer t[2] = { { .tx_buf = &mcp->addr, .len = 1, },
				     { .tx_buf = data, .len = count, }, };

	spi_message_init(&m);
	spi_message_add_tail(&t[0], &m);
	spi_message_add_tail(&t[1], &m);

	return spi_sync(spi, &m);
}

static int mcp23sxx_spi_gather_write(void *context,
				const void *reg, size_t reg_size,
				const void *val, size_t val_size)
{
	struct mcp23s08 *mcp = context;
	struct spi_device *spi = to_spi_device(mcp->dev);
	struct spi_message m;
	struct spi_transfer t[3] = { { .tx_buf = &mcp->addr, .len = 1, },
				     { .tx_buf = reg, .len = reg_size, },
				     { .tx_buf = val, .len = val_size, }, };

	spi_message_init(&m);
	spi_message_add_tail(&t[0], &m);
	spi_message_add_tail(&t[1], &m);
	spi_message_add_tail(&t[2], &m);

	return spi_sync(spi, &m);
}

static int mcp23sxx_spi_read(void *context, const void *reg, size_t reg_size,
				void *val, size_t val_size)
{
	struct mcp23s08 *mcp = context;
	struct spi_device *spi = to_spi_device(mcp->dev);
	u8 tx[2];

	if (reg_size != 1)
		return -EINVAL;

	tx[0] = mcp->addr | 0x01;
	tx[1] = *((u8 *) reg);

	return spi_write_then_read(spi, tx, sizeof(tx), val, val_size);
}

static const struct regmap_bus mcp23sxx_spi_regmap = {
	.write = mcp23sxx_spi_write,
	.gather_write = mcp23sxx_spi_gather_write,
	.read = mcp23sxx_spi_read,
};

#endif /* CONFIG_SPI_MASTER */

/*----------------------------------------------------------------------*/

/* A given spi_device can represent up to eight mcp23sxx chips
 * sharing the same chipselect but using different addresses
 * (e.g. chips #0 and #3 might be populated, but not #1 or $2).
 * Driver data holds all the per-chip data.
 */
struct mcp23s08_driver_data {
	unsigned		ngpio;
	struct mcp23s08		*mcp[8];
	struct mcp23s08		chip[];
};


static int mcp23s08_direction_input(struct gpio_chip *chip, unsigned offset)
{
	struct mcp23s08	*mcp = gpiochip_get_data(chip);
	int status;

	mutex_lock(&mcp->lock);
	status = mcp_set_bit(mcp, MCP_IODIR, offset, true);
	mutex_unlock(&mcp->lock);

	return status;
}

static int mcp23s08_get(struct gpio_chip *chip, unsigned offset)
{
	struct mcp23s08	*mcp = gpiochip_get_data(chip);
	int status, ret;

	mutex_lock(&mcp->lock);

	/* REVISIT reading this clears any IRQ ... */
	ret = mcp_read(mcp, MCP_GPIO, &status);
	if (ret < 0)
		status = 0;
	else {
		mcp->cached_gpio = status;
		status = !!(status & (1 << offset));
	}

	mutex_unlock(&mcp->lock);
	return status;
}

static int __mcp23s08_set(struct mcp23s08 *mcp, unsigned mask, bool value)
{
	return mcp_set_mask(mcp, MCP_OLAT, mask, value);
}

static void mcp23s08_set(struct gpio_chip *chip, unsigned offset, int value)
{
	struct mcp23s08	*mcp = gpiochip_get_data(chip);
	unsigned mask = BIT(offset);

	mutex_lock(&mcp->lock);
	__mcp23s08_set(mcp, mask, !!value);
	mutex_unlock(&mcp->lock);
}

static int
mcp23s08_direction_output(struct gpio_chip *chip, unsigned offset, int value)
{
	struct mcp23s08	*mcp = gpiochip_get_data(chip);
	unsigned mask = BIT(offset);
	int status;

	mutex_lock(&mcp->lock);
	status = __mcp23s08_set(mcp, mask, value);
	if (status == 0) {
		status = mcp_set_mask(mcp, MCP_IODIR, mask, false);
	}
	mutex_unlock(&mcp->lock);
	return status;
}

/*----------------------------------------------------------------------*/
static irqreturn_t mcp23s08_irq(int irq, void *data)
{
	struct mcp23s08 *mcp = data;
	int intcap, intcon, intf, i, gpio, gpio_orig, intcap_mask, defval;
	unsigned int child_irq;
	bool intf_set, intcap_changed, gpio_bit_changed,
		defval_changed, gpio_set;

	mutex_lock(&mcp->lock);
	if (mcp_read(mcp, MCP_INTF, &intf) < 0) {
		mutex_unlock(&mcp->lock);
		return IRQ_HANDLED;
	}

	if (mcp_read(mcp, MCP_INTCAP, &intcap) < 0) {
		mutex_unlock(&mcp->lock);
		return IRQ_HANDLED;
	}

	if (mcp_read(mcp, MCP_INTCON, &intcon) < 0) {
		mutex_unlock(&mcp->lock);
		return IRQ_HANDLED;
	}

	if (mcp_read(mcp, MCP_DEFVAL, &defval) < 0) {
		mutex_unlock(&mcp->lock);
		return IRQ_HANDLED;
	}

	/* This clears the interrupt(configurable on S18) */
	if (mcp_read(mcp, MCP_GPIO, &gpio) < 0) {
		mutex_unlock(&mcp->lock);
		return IRQ_HANDLED;
	}
	gpio_orig = mcp->cached_gpio;
	mcp->cached_gpio = gpio;
	mutex_unlock(&mcp->lock);

	if (intf == 0) {
		/* There is no interrupt pending */
		return IRQ_HANDLED;
	}

	dev_dbg(mcp->chip.parent,
		"intcap 0x%04X intf 0x%04X gpio_orig 0x%04X gpio 0x%04X\n",
		intcap, intf, gpio_orig, gpio);

	for (i = 0; i < mcp->chip.ngpio; i++) {
		/* We must check all of the inputs on the chip,
		 * otherwise we may not notice a change on >=2 pins.
		 *
		 * On at least the mcp23s17, INTCAP is only updated
		 * one byte at a time(INTCAPA and INTCAPB are
		 * not written to at the same time - only on a per-bank
		 * basis).
		 *
		 * INTF only contains the single bit that caused the
		 * interrupt per-bank.  On the mcp23s17, there is
		 * INTFA and INTFB.  If two pins are changed on the A
		 * side at the same time, INTF will only have one bit
		 * set.  If one pin on the A side and one pin on the B
		 * side are changed at the same time, INTF will have
		 * two bits set.  Thus, INTF can't be the only check
		 * to see if the input has changed.
		 */

		intf_set = intf & BIT(i);
		if (i < 8 && intf_set)
			intcap_mask = 0x00FF;
		else if (i >= 8 && intf_set)
			intcap_mask = 0xFF00;
		else
			intcap_mask = 0x00;

		intcap_changed = (intcap_mask &
			(intcap & BIT(i))) !=
			(intcap_mask & (BIT(i) & gpio_orig));
		gpio_set = BIT(i) & gpio;
		gpio_bit_changed = (BIT(i) & gpio_orig) !=
			(BIT(i) & gpio);
		defval_changed = (BIT(i) & intcon) &&
			((BIT(i) & gpio) !=
			(BIT(i) & defval));

		if (((gpio_bit_changed || intcap_changed) &&
			(BIT(i) & mcp->irq_rise) && gpio_set) ||
		    ((gpio_bit_changed || intcap_changed) &&
			(BIT(i) & mcp->irq_fall) && !gpio_set) ||
		    defval_changed) {
			child_irq = irq_find_mapping(mcp->chip.irq.domain, i);
			handle_nested_irq(child_irq);
		}
	}

	return IRQ_HANDLED;
}

static void mcp23s08_irq_mask(struct irq_data *data)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(data);
	struct mcp23s08 *mcp = gpiochip_get_data(gc);
	unsigned int pos = data->hwirq;

	mcp_set_bit(mcp, MCP_GPINTEN, pos, false);
}

static void mcp23s08_irq_unmask(struct irq_data *data)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(data);
	struct mcp23s08 *mcp = gpiochip_get_data(gc);
	unsigned int pos = data->hwirq;

	mcp_set_bit(mcp, MCP_GPINTEN, pos, true);
}

static int mcp23s08_irq_set_type(struct irq_data *data, unsigned int type)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(data);
	struct mcp23s08 *mcp = gpiochip_get_data(gc);
	unsigned int pos = data->hwirq;
	int status = 0;

	if ((type & IRQ_TYPE_EDGE_BOTH) == IRQ_TYPE_EDGE_BOTH) {
		mcp_set_bit(mcp, MCP_INTCON, pos, false);
		mcp->irq_rise |= BIT(pos);
		mcp->irq_fall |= BIT(pos);
	} else if (type & IRQ_TYPE_EDGE_RISING) {
		mcp_set_bit(mcp, MCP_INTCON, pos, false);
		mcp->irq_rise |= BIT(pos);
		mcp->irq_fall &= ~BIT(pos);
	} else if (type & IRQ_TYPE_EDGE_FALLING) {
		mcp_set_bit(mcp, MCP_INTCON, pos, false);
		mcp->irq_rise &= ~BIT(pos);
		mcp->irq_fall |= BIT(pos);
	} else if (type & IRQ_TYPE_LEVEL_HIGH) {
		mcp_set_bit(mcp, MCP_INTCON, pos, true);
		mcp_set_bit(mcp, MCP_DEFVAL, pos, false);
	} else if (type & IRQ_TYPE_LEVEL_LOW) {
		mcp_set_bit(mcp, MCP_INTCON, pos, true);
		mcp_set_bit(mcp, MCP_DEFVAL, pos, true);
	} else
		return -EINVAL;

	return status;
}

static void mcp23s08_irq_bus_lock(struct irq_data *data)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(data);
	struct mcp23s08 *mcp = gpiochip_get_data(gc);

	mutex_lock(&mcp->lock);
	regcache_cache_only(mcp->regmap, true);
}

static void mcp23s08_irq_bus_unlock(struct irq_data *data)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(data);
	struct mcp23s08 *mcp = gpiochip_get_data(gc);

	regcache_cache_only(mcp->regmap, false);
	regcache_sync(mcp->regmap);

	mutex_unlock(&mcp->lock);
}

static struct irq_chip mcp23s08_irq_chip = {
	.name = "gpio-mcp23xxx",
	.irq_mask = mcp23s08_irq_mask,
	.irq_unmask = mcp23s08_irq_unmask,
	.irq_set_type = mcp23s08_irq_set_type,
	.irq_bus_lock = mcp23s08_irq_bus_lock,
	.irq_bus_sync_unlock = mcp23s08_irq_bus_unlock,
};

static int mcp23s08_irq_setup(struct mcp23s08 *mcp)
{
	struct gpio_chip *chip = &mcp->chip;
	int err;
	unsigned long irqflags = IRQF_ONESHOT | IRQF_SHARED;

	if (mcp->irq_active_high)
		irqflags |= IRQF_TRIGGER_HIGH;
	else
		irqflags |= IRQF_TRIGGER_LOW;

	err = devm_request_threaded_irq(chip->parent, mcp->irq, NULL,
					mcp23s08_irq,
					irqflags, dev_name(chip->parent), mcp);
	if (err != 0) {
		dev_err(chip->parent, "unable to request IRQ#%d: %d\n",
			mcp->irq, err);
		return err;
	}

	return 0;
}

static int mcp23s08_irqchip_setup(struct mcp23s08 *mcp)
{
	struct gpio_chip *chip = &mcp->chip;
	int err;

	err =  gpiochip_irqchip_add_nested(chip,
					   &mcp23s08_irq_chip,
					   0,
					   handle_simple_irq,
					   IRQ_TYPE_NONE);
	if (err) {
		dev_err(chip->parent,
			"could not connect irqchip to gpiochip: %d\n", err);
		return err;
	}

	gpiochip_set_nested_irqchip(chip,
				    &mcp23s08_irq_chip,
				    mcp->irq);

	return 0;
}

/*----------------------------------------------------------------------*/

#ifdef CONFIG_DEBUG_FS

#include <linux/seq_file.h>

/*
 * This compares the chip's registers with the register
 * cache and corrects any incorrectly set register. This
 * can be used to fix state for MCP23xxx, that temporary
 * lost its power supply.
 */
#define MCP23S08_CONFIG_REGS 8
static int __check_mcp23s08_reg_cache(struct mcp23s08 *mcp)
{
	int cached[MCP23S08_CONFIG_REGS];
	int err = 0, i;

	/* read cached config registers */
	for (i = 0; i < MCP23S08_CONFIG_REGS; i++) {
		err = mcp_read(mcp, i, &cached[i]);
		if (err)
			goto out;
	}

	regcache_cache_bypass(mcp->regmap, true);

	for (i = 0; i < MCP23S08_CONFIG_REGS; i++) {
		int uncached;
		err = mcp_read(mcp, i, &uncached);
		if (err)
			goto out;

		if (uncached != cached[i]) {
			dev_err(mcp->dev, "restoring reg 0x%02x from 0x%04x to 0x%04x (power-loss?)\n",
				i, uncached, cached[i]);
			mcp_write(mcp, i, cached[i]);
		}
	}

out:
	if (err)
		dev_err(mcp->dev, "read error: reg=%02x, err=%d", i, err);
	regcache_cache_bypass(mcp->regmap, false);
	return err;
}

/*
 * This shows more info than the generic gpio dump code:
 * pullups, deglitching, open drain drive.
 */
static void mcp23s08_dbg_show(struct seq_file *s, struct gpio_chip *chip)
{
	struct mcp23s08	*mcp;
	char		bank;
	int		t;
	unsigned	mask;
	int iodir, gpio, gppu;

	mcp = gpiochip_get_data(chip);

	/* NOTE: we only handle one bank for now ... */
	bank = '0' + ((mcp->addr >> 1) & 0x7);

	mutex_lock(&mcp->lock);

	t = __check_mcp23s08_reg_cache(mcp);
	if (t) {
		seq_printf(s, " I/O Error\n");
		goto done;
	}
	t = mcp_read(mcp, MCP_IODIR, &iodir);
	if (t) {
		seq_printf(s, " I/O Error\n");
		goto done;
	}
	t = mcp_read(mcp, MCP_GPIO, &gpio);
	if (t) {
		seq_printf(s, " I/O Error\n");
		goto done;
	}
	t = mcp_read(mcp, MCP_GPPU, &gppu);
	if (t) {
		seq_printf(s, " I/O Error\n");
		goto done;
	}

	for (t = 0, mask = BIT(0); t < chip->ngpio; t++, mask <<= 1) {
		const char *label;

		label = gpiochip_is_requested(chip, t);
		if (!label)
			continue;

		seq_printf(s, " gpio-%-3d P%c.%d (%-12s) %s %s %s",
			chip->base + t, bank, t, label,
			(iodir & mask) ? "in " : "out",
			(gpio & mask) ? "hi" : "lo",
			(gppu & mask) ? "up" : "  ");
		/* NOTE:  ignoring the irq-related registers */
		seq_puts(s, "\n");
	}
done:
	mutex_unlock(&mcp->lock);
}

#else
#define mcp23s08_dbg_show	NULL
#endif

/*----------------------------------------------------------------------*/

static int mcp23s08_probe_one(struct mcp23s08 *mcp, struct device *dev,
			      void *data, unsigned addr, unsigned type,
			      unsigned int base, int cs)
{
	int status, ret;
	bool mirror = false;
	struct regmap_config *one_regmap_config = NULL;

	mutex_init(&mcp->lock);

	mcp->dev = dev;
	mcp->addr = addr;
	mcp->irq_active_high = false;

	mcp->chip.direction_input = mcp23s08_direction_input;
	mcp->chip.get = mcp23s08_get;
	mcp->chip.direction_output = mcp23s08_direction_output;
	mcp->chip.set = mcp23s08_set;
	mcp->chip.dbg_show = mcp23s08_dbg_show;
#ifdef CONFIG_OF_GPIO
	mcp->chip.of_gpio_n_cells = 2;
	mcp->chip.of_node = dev->of_node;
#endif

	switch (type) {
#ifdef CONFIG_SPI_MASTER
	case MCP_TYPE_S08:
	case MCP_TYPE_S17:
		switch (type) {
		case MCP_TYPE_S08:
			one_regmap_config =
				devm_kmemdup(dev, &mcp23x08_regmap,
					sizeof(struct regmap_config), GFP_KERNEL);
			mcp->reg_shift = 0;
			mcp->chip.ngpio = 8;
			mcp->chip.label = "mcp23s08";
			break;
		case MCP_TYPE_S17:
			one_regmap_config =
				devm_kmemdup(dev, &mcp23x17_regmap,
					sizeof(struct regmap_config), GFP_KERNEL);
			mcp->reg_shift = 1;
			mcp->chip.ngpio = 16;
			mcp->chip.label = "mcp23s17";
			break;
		}
		if (!one_regmap_config)
			return -ENOMEM;

		one_regmap_config->name = devm_kasprintf(dev, GFP_KERNEL, "%d", (addr & ~0x40) >> 1);
		mcp->regmap = devm_regmap_init(dev, &mcp23sxx_spi_regmap, mcp,
					       one_regmap_config);
		break;

	case MCP_TYPE_S18:
		if (!one_regmap_config)
			return -ENOMEM;
		mcp->regmap = devm_regmap_init(dev, &mcp23sxx_spi_regmap, mcp,
					       &mcp23x17_regmap);
		mcp->reg_shift = 1;
		mcp->chip.ngpio = 16;
		mcp->chip.label = "mcp23s18";
		break;
#endif /* CONFIG_SPI_MASTER */

#if IS_ENABLED(CONFIG_I2C)
	case MCP_TYPE_008:
		mcp->regmap = devm_regmap_init_i2c(data, &mcp23x08_regmap);
		mcp->reg_shift = 0;
		mcp->chip.ngpio = 8;
		mcp->chip.label = "mcp23008";
		break;

	case MCP_TYPE_017:
		mcp->regmap = devm_regmap_init_i2c(data, &mcp23x17_regmap);
		mcp->reg_shift = 1;
		mcp->chip.ngpio = 16;
		mcp->chip.label = "mcp23017";
		break;
#endif /* CONFIG_I2C */

	default:
		dev_err(dev, "invalid device type (%d)\n", type);
		return -EINVAL;
	}

	if (IS_ERR(mcp->regmap))
		return PTR_ERR(mcp->regmap);

	mcp->chip.base = base;
	mcp->chip.can_sleep = true;
	mcp->chip.parent = dev;
	mcp->chip.owner = THIS_MODULE;

	/* verify MCP_IOCON.SEQOP = 0, so sequential reads work,
	 * and MCP_IOCON.HAEN = 1, so we work with all chips.
	 */

	ret = mcp_read(mcp, MCP_IOCON, &status);
	if (ret < 0)
		goto fail;

	mcp->irq_controller =
		device_property_read_bool(dev, "interrupt-controller");
	if (mcp->irq && mcp->irq_controller) {
		mcp->irq_active_high =
			device_property_read_bool(dev,
					      "microchip,irq-active-high");

		mirror = device_property_read_bool(dev, "microchip,irq-mirror");
	}

	if ((status & IOCON_SEQOP) || !(status & IOCON_HAEN) || mirror ||
	     mcp->irq_active_high) {
		/* mcp23s17 has IOCON twice, make sure they are in sync */
		status &= ~(IOCON_SEQOP | (IOCON_SEQOP << 8));
		status |= IOCON_HAEN | (IOCON_HAEN << 8);
		if (mcp->irq_active_high)
			status |= IOCON_INTPOL | (IOCON_INTPOL << 8);
		else
			status &= ~(IOCON_INTPOL | (IOCON_INTPOL << 8));

		if (mirror)
			status |= IOCON_MIRROR | (IOCON_MIRROR << 8);

		if (type == MCP_TYPE_S18)
			status |= IOCON_INTCC | (IOCON_INTCC << 8);

		ret = mcp_write(mcp, MCP_IOCON, status);
		if (ret < 0)
			goto fail;
	}

	if (mcp->irq && mcp->irq_controller) {
		ret = mcp23s08_irqchip_setup(mcp);
		if (ret)
			goto fail;
	}

	ret = devm_gpiochip_add_data(dev, &mcp->chip, mcp);
	if (ret < 0)
		goto fail;

	mcp->pinctrl_desc.name = "mcp23xxx-pinctrl";
	mcp->pinctrl_desc.pctlops = &mcp_pinctrl_ops;
	mcp->pinctrl_desc.confops = &mcp_pinconf_ops;
	mcp->pinctrl_desc.npins = mcp->chip.ngpio;
	if (mcp->pinctrl_desc.npins == 8)
		mcp->pinctrl_desc.pins = mcp23x08_pins;
	else if (mcp->pinctrl_desc.npins == 16)
		mcp->pinctrl_desc.pins = mcp23x17_pins;
	mcp->pinctrl_desc.owner = THIS_MODULE;

	mcp->pctldev = devm_pinctrl_register(dev, &mcp->pinctrl_desc, mcp);
	if (IS_ERR(mcp->pctldev)) {
		ret = PTR_ERR(mcp->pctldev);
		goto fail;
	}

	if (mcp->irq)
		ret = mcp23s08_irq_setup(mcp);

fail:
	if (ret < 0)
		dev_dbg(dev, "can't setup chip %d, --> %d\n", addr, ret);
	return ret;
}

/*----------------------------------------------------------------------*/

#ifdef CONFIG_OF
#ifdef CONFIG_SPI_MASTER
static const struct of_device_id mcp23s08_spi_of_match[] = {
	{
		.compatible = "microchip,mcp23s08",
		.data = (void *) MCP_TYPE_S08,
	},
	{
		.compatible = "microchip,mcp23s17",
		.data = (void *) MCP_TYPE_S17,
	},
	{
		.compatible = "microchip,mcp23s18",
		.data = (void *) MCP_TYPE_S18,
	},
/* NOTE: The use of the mcp prefix is deprecated and will be removed. */
	{
		.compatible = "mcp,mcp23s08",
		.data = (void *) MCP_TYPE_S08,
	},
	{
		.compatible = "mcp,mcp23s17",
		.data = (void *) MCP_TYPE_S17,
	},
	{ },
};
MODULE_DEVICE_TABLE(of, mcp23s08_spi_of_match);
#endif

#if IS_ENABLED(CONFIG_I2C)
static const struct of_device_id mcp23s08_i2c_of_match[] = {
	{
		.compatible = "microchip,mcp23008",
		.data = (void *) MCP_TYPE_008,
	},
	{
		.compatible = "microchip,mcp23017",
		.data = (void *) MCP_TYPE_017,
	},
/* NOTE: The use of the mcp prefix is deprecated and will be removed. */
	{
		.compatible = "mcp,mcp23008",
		.data = (void *) MCP_TYPE_008,
	},
	{
		.compatible = "mcp,mcp23017",
		.data = (void *) MCP_TYPE_017,
	},
	{ },
};
MODULE_DEVICE_TABLE(of, mcp23s08_i2c_of_match);
#endif
#endif /* CONFIG_OF */


#if IS_ENABLED(CONFIG_I2C)

static int mcp230xx_probe(struct i2c_client *client,
				    const struct i2c_device_id *id)
{
	struct mcp23s08_platform_data *pdata, local_pdata;
	struct mcp23s08 *mcp;
	int status;

	pdata = dev_get_platdata(&client->dev);
	if (!pdata) {
		pdata = &local_pdata;
		pdata->base = -1;
	}

	mcp = devm_kzalloc(&client->dev, sizeof(*mcp), GFP_KERNEL);
	if (!mcp)
		return -ENOMEM;

	mcp->irq = client->irq;
	status = mcp23s08_probe_one(mcp, &client->dev, client, client->addr,
				    id->driver_data, pdata->base, 0);
	if (status)
		return status;

	i2c_set_clientdata(client, mcp);

	return 0;
}

static const struct i2c_device_id mcp230xx_id[] = {
	{ "mcp23008", MCP_TYPE_008 },
	{ "mcp23017", MCP_TYPE_017 },
	{ },
};
MODULE_DEVICE_TABLE(i2c, mcp230xx_id);

static struct i2c_driver mcp230xx_driver = {
	.driver = {
		.name	= "mcp230xx",
		.of_match_table = of_match_ptr(mcp23s08_i2c_of_match),
	},
	.probe		= mcp230xx_probe,
	.id_table	= mcp230xx_id,
};

static int __init mcp23s08_i2c_init(void)
{
	return i2c_add_driver(&mcp230xx_driver);
}

static void mcp23s08_i2c_exit(void)
{
	i2c_del_driver(&mcp230xx_driver);
}

#else

static int __init mcp23s08_i2c_init(void) { return 0; }
static void mcp23s08_i2c_exit(void) { }

#endif /* CONFIG_I2C */

/*----------------------------------------------------------------------*/

#ifdef CONFIG_SPI_MASTER

static int mcp23s08_probe(struct spi_device *spi)
{
	struct mcp23s08_platform_data	*pdata, local_pdata;
	unsigned			addr;
	int				chips = 0;
	struct mcp23s08_driver_data	*data;
	int				status, type;
	unsigned			ngpio = 0;
	const struct			of_device_id *match;

	match = of_match_device(of_match_ptr(mcp23s08_spi_of_match), &spi->dev);
	if (match)
		type = (int)(uintptr_t)match->data;
	else
		type = spi_get_device_id(spi)->driver_data;

	pdata = dev_get_platdata(&spi->dev);
	if (!pdata) {
		pdata = &local_pdata;
		pdata->base = -1;

		status = device_property_read_u32(&spi->dev,
			"microchip,spi-present-mask", &pdata->spi_present_mask);
		if (status) {
			status = device_property_read_u32(&spi->dev,
				"mcp,spi-present-mask",
				&pdata->spi_present_mask);

			if (status) {
				dev_err(&spi->dev, "missing spi-present-mask");
				return -ENODEV;
			}
		}
	}

	if (!pdata->spi_present_mask || pdata->spi_present_mask > 0xff) {
		dev_err(&spi->dev, "invalid spi-present-mask");
		return -ENODEV;
	}

	for (addr = 0; addr < MCP_MAX_DEV_PER_CS; addr++) {
		if (pdata->spi_present_mask & BIT(addr))
			chips++;
	}

	if (!chips)
		return -ENODEV;

	data = devm_kzalloc(&spi->dev,
			    sizeof(*data) + chips * sizeof(struct mcp23s08),
			    GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	spi_set_drvdata(spi, data);

	for (addr = 0; addr < MCP_MAX_DEV_PER_CS; addr++) {
		if (!(pdata->spi_present_mask & BIT(addr)))
			continue;
		chips--;
		data->mcp[addr] = &data->chip[chips];
		data->mcp[addr]->irq = spi->irq;
		status = mcp23s08_probe_one(data->mcp[addr], &spi->dev, spi,
					    0x40 | (addr << 1), type,
					    pdata->base, addr);
		if (status < 0)
			return status;

		if (pdata->base != -1)
			pdata->base += data->mcp[addr]->chip.ngpio;
		ngpio += data->mcp[addr]->chip.ngpio;
	}
	data->ngpio = ngpio;

	return 0;
}

static const struct spi_device_id mcp23s08_ids[] = {
	{ "mcp23s08", MCP_TYPE_S08 },
	{ "mcp23s17", MCP_TYPE_S17 },
	{ "mcp23s18", MCP_TYPE_S18 },
	{ },
};
MODULE_DEVICE_TABLE(spi, mcp23s08_ids);

static struct spi_driver mcp23s08_driver = {
	.probe		= mcp23s08_probe,
	.id_table	= mcp23s08_ids,
	.driver = {
		.name	= "mcp23s08",
		.of_match_table = of_match_ptr(mcp23s08_spi_of_match),
	},
};

static int __init mcp23s08_spi_init(void)
{
	return spi_register_driver(&mcp23s08_driver);
}

static void mcp23s08_spi_exit(void)
{
	spi_unregister_driver(&mcp23s08_driver);
}

#else

static int __init mcp23s08_spi_init(void) { return 0; }
static void mcp23s08_spi_exit(void) { }

#endif /* CONFIG_SPI_MASTER */

/*----------------------------------------------------------------------*/

static int __init mcp23s08_init(void)
{
	int ret;

	ret = mcp23s08_spi_init();
	if (ret)
		goto spi_fail;

	ret = mcp23s08_i2c_init();
	if (ret)
		goto i2c_fail;

	return 0;

 i2c_fail:
	mcp23s08_spi_exit();
 spi_fail:
	return ret;
}
/* register after spi/i2c postcore initcall and before
 * subsys initcalls that may rely on these GPIOs
 */
subsys_initcall(mcp23s08_init);

static void __exit mcp23s08_exit(void)
{
	mcp23s08_spi_exit();
	mcp23s08_i2c_exit();
}
module_exit(mcp23s08_exit);

MODULE_LICENSE("GPL");