tjh.dev
Linux kernel mirror (for testing)
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kernel
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linux
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 */