diff options
| -rw-r--r-- | drivers/gpio/Kconfig | 23 | ||||
| -rw-r--r-- | drivers/gpio/Makefile | 1 | ||||
| -rw-r--r-- | drivers/gpio/pcf857x.c | 330 | ||||
| -rw-r--r-- | include/linux/i2c/pcf857x.h | 45 |
4 files changed, 399 insertions, 0 deletions
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig index 560687c..36d5d6a 100644 --- a/drivers/gpio/Kconfig +++ b/drivers/gpio/Kconfig @@ -27,6 +27,29 @@ config DEBUG_GPIO comment "I2C GPIO expanders:" +config GPIO_PCF857X + tristate "PCF857x, PCA857x, and PCA967x I2C GPIO expanders" + depends on I2C + help + Say yes here to provide access to most "quasi-bidirectional" I2C + GPIO expanders used for additional digital outputs or inputs. + Most of these parts are from NXP, though TI is a second source for + some of them. Compatible models include: + + 8 bits: pcf8574, pcf8574a, pca8574, pca8574a, + pca9670, pca9672, pca9674, pca9674a + + 16 bits: pcf8575, pcf8575c, pca8575, + pca9671, pca9673, pca9675 + + Your board setup code will need to declare the expanders in + use, and assign numbers to the GPIOs they expose. Those GPIOs + can then be used from drivers and other kernel code, just like + other GPIOs, but only accessible from task contexts. + + This driver provides an in-kernel interface to those GPIOs using + platform-neutral GPIO calls. + comment "SPI GPIO expanders:" endmenu diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile index c3da039..b469ab2 100644 --- a/drivers/gpio/Makefile +++ b/drivers/gpio/Makefile @@ -4,3 +4,4 @@ ccflags-$(CONFIG_DEBUG_GPIO) += -DDEBUG obj-$(CONFIG_HAVE_GPIO_LIB) += gpiolib.o +obj-$(CONFIG_GPIO_PCF857X) += pcf857x.o diff --git a/drivers/gpio/pcf857x.c b/drivers/gpio/pcf857x.c new file mode 100644 index 0000000..c6b3b53 --- /dev/null +++ b/drivers/gpio/pcf857x.c @@ -0,0 +1,330 @@ +/* + * 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"); diff --git a/include/linux/i2c/pcf857x.h b/include/linux/i2c/pcf857x.h new file mode 100644 index 0000000..ba8ea6e --- /dev/null +++ b/include/linux/i2c/pcf857x.h @@ -0,0 +1,45 @@ +#ifndef __LINUX_PCF857X_H +#define __LINUX_PCF857X_H + +/** + * struct pcf857x_platform_data - data to set up pcf857x driver + * @gpio_base: number of the chip's first GPIO + * @n_latch: optional bit-inverse of initial register value; if + * you leave this initialized to zero the driver will act + * like the chip was just reset + * @setup: optional callback issued once the GPIOs are valid + * @teardown: optional callback issued before the GPIOs are invalidated + * @context: optional parameter passed to setup() and teardown() + * + * In addition to the I2C_BOARD_INFO() state appropriate to each chip, + * the i2c_board_info used with the pcf875x driver must provide the + * chip "type" ("pcf8574", "pcf8574a", "pcf8575", "pcf8575c") and its + * platform_data (pointer to one of these structures) with at least + * the gpio_base value initialized. + * + * The @setup callback may be used with the kind of board-specific glue + * which hands the (now-valid) GPIOs to other drivers, or which puts + * devices in their initial states using these GPIOs. + * + * These GPIO chips are only "quasi-bidirectional"; read the chip specs + * to understand the behavior. They don't have separate registers to + * record which pins are used for input or output, record which output + * values are driven, or provide access to input values. That must be + * inferred by reading the chip's value and knowing the last value written + * to it. If you leave n_latch initialized to zero, that last written + * value is presumed to be all ones (as if the chip were just reset). + */ +struct pcf857x_platform_data { + unsigned gpio_base; + unsigned n_latch; + + int (*setup)(struct i2c_client *client, + int gpio, unsigned ngpio, + void *context); + int (*teardown)(struct i2c_client *client, + int gpio, unsigned ngpio, + void *context); + void *context; +}; + +#endif /* __LINUX_PCF857X_H */ |
