From 15fae37d9f5f21571a9618d8353164b6ddfea6f6 Mon Sep 17 00:00:00 2001 From: David Brownell Date: Mon, 4 Feb 2008 22:28:24 -0800 Subject: gpiolib: pcf857x i2c gpio expander support This is a new-style I2C driver for most common 8 and 16 bit I2C based "quasi-bidirectional" GPIO expanders: pcf8574 or pcf8575, and several compatible models (mostly faster, supporting I2C at up to 1 MHz). 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 has been a big factor in the proliferation of board-specific drivers for these chips... stuff that rarely makes it upstream since it's so ugly. This driver will let such boards use standard calls. Since it's a new-style driver, these devices must be configured as part of board-specific init. That eliminates the need for error-prone manual configuration of module parameters, and makes compatibility with legacy drivers (pcf8574.c, pc8575.c) for these chips easier (there's a clear either/or disjunction). Signed-off-by: David Brownell Acked-by: Jean Delvare Cc: Eric Miao Cc: Sam Ravnborg Cc: Haavard Skinnemoen Cc: Philipp Zabel Cc: Russell King Cc: Ben Gardner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/i2c/pcf857x.h | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 include/linux/i2c/pcf857x.h (limited to 'include/linux/i2c') diff --git a/include/linux/i2c/pcf857x.h b/include/linux/i2c/pcf857x.h new file mode 100644 index 00000000000..ba8ea6e1647 --- /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 */ -- cgit v1.2.3