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Message-Id: <200710291851.49057.david-b@pacbell.net> Date: Mon, 29 Oct 2007 18:51:48 -0700 From: David Brownell <david-b@...bell.net> To: Linux Kernel list <linux-kernel@...r.kernel.org> Cc: Felipe Balbi <felipebalbi@...rs.sourceforge.net>, Bill Gatliff <bgat@...lgatliff.com>, Haavard Skinnemoen <hskinnemoen@...el.com>, Andrew Victor <andrew@...people.com>, Tony Lindgren <tony@...mide.com>, Jean Delvare <khali@...ux-fr.org>, "eric miao" <eric.y.miao@...il.com>, Kevin Hilman <khilman@...sta.com>, Paul Mundt <lethal@...ux-sh.org>, Ben Dooks <ben@...nity.fluff.org> Subject: [patch/rfc 2/4] pcf875x I2C GPIO expander driver This is a new-style I2C driver for some common 8 and 16 bit I2C based GPIO expanders: pcf8574 and pcf8575. Since it's a new-style driver, it's configured as part of board-specific init ... eliminating the need for error-prone manual configuration of module parameters. The driver exposes the GPIO signals using the platform-neutral GPIO programming interface, so they are easily accessed by other kernel code. The lack of such a flexible kernel API is what has ensured the proliferation of board-specific hacks for these chips... stuff that rarely makes it upstream since it's so ugly. This driver will let such board-specific code use standard GPIO calls. Signed-off-by: David Brownell <dbrownell@...rs.sourceforge.net> --- Note that there's currently a drivers/i2c/chips/pcf8574.c driver. Key differences include: this one talks to other kernel code so it can use the GPIOs "normally", but that one talks to userspace through sysfs. Also, this one is a "new style" I2C driver, so it's smaller and doesn't need all those error-prone module parameters. Plus, this one handles both 8 and 16 bit chip versions. drivers/i2c/chips/Kconfig | 18 ++ drivers/i2c/chips/Makefile | 1 drivers/i2c/chips/pcf857x.c | 309 ++++++++++++++++++++++++++++++++++++++++++++ include/linux/pcf857x.h | 43 ++++++ 4 files changed, 371 insertions(+) --- a/drivers/i2c/chips/Kconfig 2007-10-28 21:04:06.000000000 -0700 +++ b/drivers/i2c/chips/Kconfig 2007-10-29 14:16:01.000000000 -0700 @@ -51,6 +51,24 @@ config SENSORS_EEPROM This driver can also be built as a module. If so, the module will be called eeprom. +config GPIO_PCF857X + tristate "PCF875x GPIO expanders" + depends on GPIO_LIB + help + Say yes here to provide access to some I2C GPIO expanders which + may be used for additional digital outputs or inputs: + + - pcf8574, pcf8574a ... 8 bits, from NXP or TI + - pcf8575, pcf8575c ... 16 bits, from NXP or TI + + 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 only an in-kernel interface to those GPIOs. + Any sysfs interface to userspace would be provided separately. + config SENSORS_PCF8574 tristate "Philips PCF8574 and PCF8574A" depends on EXPERIMENTAL --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ b/include/linux/pcf857x.h 2007-10-28 21:09:49.000000000 -0700 @@ -0,0 +1,43 @@ +#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 output state + * @context: optional parameter passed to setup() and teardown() + * @setup: optional callback issued once the GPIOs are valid + * @teardown: optional callback issued before the GPIOs are invvalidated + * + * 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. + * + * Since these GPIO chips don't have conventional registers recording + * whether a pin is used for input or output, or an output latch to + * record the values being driven, the n_latch value may be used to + * avoid intialization glitches. Its inverted value initializes the + * value into which bits are masked before they're written to the PCF + * chip. That means that if it's left at zero, the chip is treated as + * if it came from power-up reset. + */ +struct pcf857x_platform_data { + unsigned gpio_base; + unsigned n_latch; + + void *context; + int (*setup)(struct i2c_client *client, + int gpio, unsigned ngpio, + void *context); + int (*teardown)(struct i2c_client *client, + int gpio, unsigned ngpio, + void *context); +}; + +#endif /* __LINUX_PCF857X_H */ --- a/drivers/i2c/chips/Makefile 2007-10-28 21:04:06.000000000 -0700 +++ b/drivers/i2c/chips/Makefile 2007-10-28 21:09:49.000000000 -0700 @@ -11,6 +11,7 @@ obj-$(CONFIG_SENSORS_M41T00) += m41t00.o obj-$(CONFIG_SENSORS_PCA9539) += pca9539.o obj-$(CONFIG_SENSORS_PCF8574) += pcf8574.o obj-$(CONFIG_SENSORS_PCF8591) += pcf8591.o +obj-$(CONFIG_GPIO_PCF857X) += pcf857x.o obj-$(CONFIG_ISP1301_OMAP) += isp1301_omap.o obj-$(CONFIG_TPS65010) += tps65010.o obj-$(CONFIG_SENSORS_TLV320AIC23) += tlv320aic23.o --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ b/drivers/i2c/chips/pcf857x.c 2007-10-29 14:12:21.000000000 -0700 @@ -0,0 +1,309 @@ +/* + * pcf857x - driver for pcf857{4,4a,5,5c} 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/i2c.h> +#include <linux/pcf857x.h> + +#include <asm/gpio.h> + + +/* + * The pcf857x chips only expose a one read register 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 it acts a bit like that. + * + * Some other I2C GPIO expander chips (like the pca9534, pca9535, pca9555, + * pca9539, mcp23008, and mc23017) have a more complex register model with + * more conventional input circuitry, often using 0x20..0x27 addresses. + */ +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, (u8) 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, (u8) 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, (u16) 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, (u16) 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 = 0; + + 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. + */ + + /* '74a addresses are 0x38..0x3f; '74 uses 0x20..0x27 */ + if (strcmp(client->name, "pcf8574a") == 0 + || strcmp(client->name, "pcf8574") == 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 */ + 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. + */ + } else if (strcmp(client->name, "pcf8575c") == 0 + || strcmp(client->name, "pcf8575") == 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 */ + status = i2c_read_le16(client); + + } else + status = -ENODEV; + + if (status < 0) { + dev_dbg(&client->dev, "probe error %d for '%s'\n", + status, client->name); + kfree(gpio); + return status; + } + + gpio->chip.label = client->name; + + gpio->client = client; + i2c_set_clientdata(client, gpio); + + /* NOTE: these chips have strange "pseudo-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. + * + * We use pdata->n_latch to avoid trouble. In the typical case it's + * left initialized to zero; our software copy of the "latch" then + * matches the chip's reset state. But there may be cases where a + * system must drive some pins low, without transient glitching. + * Handle those cases by assigning n_latch to a nonzero value. + */ + gpio->out = ~pdata->n_latch; + + status = gpiochip_add(&gpio->chip); + if (status < 0) { + kfree(gpio); + return status; + } + + /* 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 can use them. + */ + if (pdata->setup) { + status = pdata->setup(client, + gpio->chip.base, gpio->chip.ngpio, + pdata->context); + if (status < 0) + dev_dbg(&client->dev, "setup --> %d\n", status); + } + + return 0; +} + +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); +} +/* we want GPIOs to be ready at device_initcall() time */ +subsys_initcall(pcf857x_init); + +static void __exit pcf857x_exit(void) +{ + i2c_del_driver(&pcf857x_driver); +} +module_exit(pcf857x_exit); + +MODULE_LICENSE("GPL"); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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