linux/drivers/gpio/pcf857x.c

/*
 * 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;
	gpio->chip.owner = THIS_MODULE;

	/* 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");