/*
* 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>
static const struct i2c_device_id pcf857x_id[] = {
{ "pcf8574", 8 },
{ "pca8574", 8 },
{ "pca9670", 8 },
{ "pca9672", 8 },
{ "pca9674", 8 },
{ "pcf8575", 16 },
{ "pca8575", 16 },
{ "pca9671", 16 },
{ "pca9673", 16 },
{ "pca9675", 16 },
{ }
};
MODULE_DEVICE_TABLE(i2c, pcf857x_id);
/*
* 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,
const struct i2c_device_id *id)
{
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.
*/
gpio->chip.ngpio = id->driver_data;
if (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 (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,
.id_table = pcf857x_id,
};
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");
