/*
 * pcf857x - driver for pcf857x, pca857x, and pca967x I2C GPIO expanders
 *
 * Copyright (C) 2007 David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/i2c/pcf857x.h>

#include <asm/gpio.h>


/*
 * The pcf857x, pca857x, and pca967x chips only expose one read and one
 * write register.  Writing a "one" bit (to match the reset state) lets
 * that pin be used as an input; it's not an open-drain model, but acts
 * a bit like one.  This is described as "quasi-bidirectional"; read the
 * chip documentation for details.
 *
 * Many other I2C GPIO expander chips (like the pca953x models) have
 * more complex register models and more conventional circuitry using
 * push/pull drivers.  They often use the same 0x20..0x27 addresses as
 * pcf857x parts, making the "legacy" I2C driver model problematic.
 */
struct pcf857x {
        struct gpio_chip        chip;
        struct i2c_client       *client;
        unsigned                out;            /* software latch */
};

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

/* Talk to 8-bit I/O expander */

static int pcf857x_input8(struct gpio_chip *chip, unsigned offset)
{
        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);

        gpio->out |= (1 << offset);
        return i2c_smbus_write_byte(gpio->client, gpio->out);
}

static int pcf857x_get8(struct gpio_chip *chip, unsigned offset)
{
        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
        s32             value;

        value = i2c_smbus_read_byte(gpio->client);
        return (value < 0) ? 0 : (value & (1 << offset));
}

static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value)
{
        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
        unsigned        bit = 1 << offset;

        if (value)
                gpio->out |= bit;
        else
                gpio->out &= ~bit;
        return i2c_smbus_write_byte(gpio->client, gpio->out);
}

static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value)
{
        pcf857x_output8(chip, offset, value);
}

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

/* Talk to 16-bit I/O expander */

static int i2c_write_le16(struct i2c_client *client, u16 word)
{
        u8 buf[2] = { word & 0xff, word >> 8, };
        int status;

        status = i2c_master_send(client, buf, 2);
        return (status < 0) ? status : 0;
}

static int i2c_read_le16(struct i2c_client *client)
{
        u8 buf[2];
        int status;

        status = i2c_master_recv(client, buf, 2);
        if (status < 0)
                return status;
        return (buf[1] << 8) | buf[0];
}

static int pcf857x_input16(struct gpio_chip *chip, unsigned offset)
{
        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);

        gpio->out |= (1 << offset);
        return i2c_write_le16(gpio->client, gpio->out);
}

static int pcf857x_get16(struct gpio_chip *chip, unsigned offset)
{
        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
        int             value;

        value = i2c_read_le16(gpio->client);
        return (value < 0) ? 0 : (value & (1 << offset));
}

static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value)
{
        struct pcf857x  *gpio = container_of(chip, struct pcf857x, chip);
        unsigned        bit = 1 << offset;

        if (value)
                gpio->out |= bit;
        else
                gpio->out &= ~bit;
        return i2c_write_le16(gpio->client, gpio->out);
}

static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value)
{
        pcf857x_output16(chip, offset, value);
}

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

static int pcf857x_probe(struct i2c_client *client)
{
        struct pcf857x_platform_data    *pdata;
        struct pcf857x                  *gpio;
        int                             status;

        pdata = client->dev.platform_data;
        if (!pdata)
                return -ENODEV;

        /* Allocate, initialize, and register this gpio_chip. */
        gpio = kzalloc(sizeof *gpio, GFP_KERNEL);
        if (!gpio)
                return -ENOMEM;

        gpio->chip.base = pdata->gpio_base;
        gpio->chip.can_sleep = 1;

        /* NOTE:  the OnSemi jlc1562b is also largely compatible with
         * these parts, notably for output.  It has a low-resolution
         * DAC instead of pin change IRQs; and its inputs can be the
         * result of comparators.
         */

        /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f;
         * 9670, 9672, 9764, and 9764a use quite a variety.
         *
         * NOTE: we don't distinguish here between *4 and *4a parts.
         */
        if (strcmp(client->name, "pcf8574") == 0
                        || strcmp(client->name, "pca8574") == 0
                        || strcmp(client->name, "pca9670") == 0
                        || strcmp(client->name, "pca9672") == 0
                        || strcmp(client->name, "pca9674") == 0
                        ) {
                gpio->chip.ngpio = 8;
                gpio->chip.direction_input = pcf857x_input8;
                gpio->chip.get = pcf857x_get8;
                gpio->chip.direction_output = pcf857x_output8;
                gpio->chip.set = pcf857x_set8;

                if (!i2c_check_functionality(client->adapter,
                                I2C_FUNC_SMBUS_BYTE))
                        status = -EIO;

                /* fail if there's no chip present */
                else
                        status = i2c_smbus_read_byte(client);

        /* '75/'75c addresses are 0x20..0x27, just like the '74;
         * the '75c doesn't have a current source pulling high.
         * 9671, 9673, and 9765 use quite a variety of addresses.
         *
         * NOTE: we don't distinguish here between '75 and '75c parts.
         */
        } else if (strcmp(client->name, "pcf8575") == 0
                        || strcmp(client->name, "pca8575") == 0
                        || strcmp(client->name, "pca9671") == 0
                        || strcmp(client->name, "pca9673") == 0
                        || strcmp(client->name, "pca9675") == 0
                        ) {
                gpio->chip.ngpio = 16;
                gpio->chip.direction_input = pcf857x_input16;
                gpio->chip.get = pcf857x_get16;
                gpio->chip.direction_output = pcf857x_output16;
                gpio->chip.set = pcf857x_set16;

                if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
                        status = -EIO;

                /* fail if there's no chip present */
                else
                        status = i2c_read_le16(client);

        } else
                status = -ENODEV;

        if (status < 0)
                goto fail;

        gpio->chip.label = client->name;

        gpio->client = client;
        i2c_set_clientdata(client, gpio);

        /* NOTE:  these chips have strange "quasi-bidirectional" I/O pins.
         * We can't actually know whether a pin is configured (a) as output
         * and driving the signal low, or (b) as input and reporting a low
         * value ... without knowing the last value written since the chip
         * came out of reset (if any).  We can't read the latched output.
         *
         * In short, the only reliable solution for setting up pin direction
         * is to do it explicitly.  The setup() method can do that, but it
         * may cause transient glitching since it can't know the last value
         * written (some pins may need to be driven low).
         *
         * Using pdata->n_latch avoids that trouble.  When left initialized
         * to zero, our software copy of the "latch" then matches the chip's
         * all-ones reset state.  Otherwise it flags pins to be driven low.
         */
        gpio->out = ~pdata->n_latch;

        status = gpiochip_add(&gpio->chip);
        if (status < 0)
                goto fail;

        /* NOTE: these chips can issue "some pin-changed" IRQs, which we
         * don't yet even try to use.  Among other issues, the relevant
         * genirq state isn't available to modular drivers; and most irq
         * methods can't be called from sleeping contexts.
         */

        dev_info(&client->dev, "gpios %d..%d on a %s%s\n",
                        gpio->chip.base,
                        gpio->chip.base + gpio->chip.ngpio - 1,
                        client->name,
                        client->irq ? " (irq ignored)" : "");

        /* Let platform code set up the GPIOs and their users.
         * Now is the first time anyone could use them.
         */
        if (pdata->setup) {
                status = pdata->setup(client,
                                gpio->chip.base, gpio->chip.ngpio,
                                pdata->context);
                if (status < 0)
                        dev_warn(&client->dev, "setup --> %d\n", status);
        }

        return 0;

fail:
        dev_dbg(&client->dev, "probe error %d for '%s'\n",
                        status, client->name);
        kfree(gpio);
        return status;
}

static int pcf857x_remove(struct i2c_client *client)
{
        struct pcf857x_platform_data    *pdata = client->dev.platform_data;
        struct pcf857x                  *gpio = i2c_get_clientdata(client);
        int                             status = 0;

        if (pdata->teardown) {
                status = pdata->teardown(client,
                                gpio->chip.base, gpio->chip.ngpio,
                                pdata->context);
                if (status < 0) {
                        dev_err(&client->dev, "%s --> %d\n",
                                        "teardown", status);
                        return status;
                }
        }

        status = gpiochip_remove(&gpio->chip);
        if (status == 0)
                kfree(gpio);
        else
                dev_err(&client->dev, "%s --> %d\n", "remove", status);
        return status;
}

static struct i2c_driver pcf857x_driver = {
        .driver = {
                .name   = "pcf857x",
                .owner  = THIS_MODULE,
        },
        .probe  = pcf857x_probe,
        .remove = pcf857x_remove,
};

static int __init pcf857x_init(void)
{
        return i2c_add_driver(&pcf857x_driver);
}
module_init(pcf857x_init);

static void __exit pcf857x_exit(void)
{
        i2c_del_driver(&pcf857x_driver);
}
module_exit(pcf857x_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Brownell");