include/linux/i2c/pcf857x.h

   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 its
  16  * platform_data (pointer to one of these structures) with at least
  17  * the gpio_base value initialized.
  18  *
  19  * The @setup callback may be used with the kind of board-specific glue
  20  * which hands the (now-valid) GPIOs to other drivers, or which puts
  21  * devices in their initial states using these GPIOs.
  22  *
  23  * These GPIO chips are only "quasi-bidirectional"; read the chip specs
  24  * to understand the behavior.  They don't have separate registers to
  25  * record which pins are used for input or output, record which output
  26  * values are driven, or provide access to input values.  That must be
  27  * inferred by reading the chip's value and knowing the last value written
  28  * to it.  If you leave n_latch initialized to zero, that last written
  29  * value is presumed to be all ones (as if the chip were just reset).
  30  */
  31 struct pcf857x_platform_data {
  32         unsigned        gpio_base;
  33         unsigned        n_latch;
  34
  35         int             (*setup)(struct i2c_client *client,
  36                                         int gpio, unsigned ngpio,
  37                                         void *context);
  38         int             (*teardown)(struct i2c_client *client,
  39                                         int gpio, unsigned ngpio,
  40                                         void *context);
  41         void            *context;
  42 };
  43
  44 #endif /* __LINUX_PCF857X_H */