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authorDavid Brownell <dbrownell@users.sourceforge.net>2008-02-05 01:28:24 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-05 12:44:13 -0500
commit15fae37d9f5f21571a9618d8353164b6ddfea6f6 (patch)
tree13b4fb5479cf3a9522c6673cc6ccae20b6658e55 /include
parent1c44f5f16fee880b294f8068354bfb9dddf1349b (diff)
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 <dbrownell@users.sourceforge.net> Acked-by: Jean Delvare <khali@linux-fr.org> Cc: Eric Miao <eric.miao@marvell.com> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Haavard Skinnemoen <hskinnemoen@atmel.com> Cc: Philipp Zabel <philipp.zabel@gmail.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Ben Gardner <bgardner@wabtec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/i2c/pcf857x.h45
1 files changed, 45 insertions, 0 deletions
diff --git a/include/linux/i2c/pcf857x.h b/include/linux/i2c/pcf857x.h
new file mode 100644
index 000000000000..ba8ea6e16476
--- /dev/null
+++ b/include/linux/i2c/pcf857x.h
@@ -0,0 +1,45 @@
1#ifndef __LINUX_PCF857X_H
2#define __LINUX_PCF857X_H
3
4/**
5 * struct pcf857x_platform_data - data to set up pcf857x driver
6 * @gpio_base: number of the chip's first GPIO
7 * @n_latch: optional bit-inverse of initial register value; if
8 * you leave this initialized to zero the driver will act
9 * like the chip was just reset
10 * @setup: optional callback issued once the GPIOs are valid
11 * @teardown: optional callback issued before the GPIOs are invalidated
12 * @context: optional parameter passed to setup() and teardown()
13 *
14 * In addition to the I2C_BOARD_INFO() state appropriate to each chip,
15 * the i2c_board_info used with the pcf875x driver must provide the
16 * chip "type" ("pcf8574", "pcf8574a", "pcf8575", "pcf8575c") and its
17 * platform_data (pointer to one of these structures) with at least
18 * the gpio_base value initialized.
19 *
20 * The @setup callback may be used with the kind of board-specific glue
21 * which hands the (now-valid) GPIOs to other drivers, or which puts
22 * devices in their initial states using these GPIOs.
23 *
24 * These GPIO chips are only "quasi-bidirectional"; read the chip specs
25 * to understand the behavior. They don't have separate registers to
26 * record which pins are used for input or output, record which output
27 * values are driven, or provide access to input values. That must be
28 * inferred by reading the chip's value and knowing the last value written
29 * to it. If you leave n_latch initialized to zero, that last written
30 * value is presumed to be all ones (as if the chip were just reset).
31 */
32struct pcf857x_platform_data {
33 unsigned gpio_base;
34 unsigned n_latch;
35
36 int (*setup)(struct i2c_client *client,
37 int gpio, unsigned ngpio,
38 void *context);
39 int (*teardown)(struct i2c_client *client,
40 int gpio, unsigned ngpio,
41 void *context);
42 void *context;
43};
44
45#endif /* __LINUX_PCF857X_H */