gpio.h
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/*
* Copyright (c) 2011 The Chromium OS Authors.
* Copyright (c) 2011, NVIDIA Corp. All rights reserved.
* SPDX-License-Identifier: GPL-2.0+
*/
#ifndef _ASM_GENERIC_GPIO_H_
#define _ASM_GENERIC_GPIO_H_
/*
* Generic GPIO API for U-Boot
*
* GPIOs are numbered from 0 to GPIO_COUNT-1 which value is defined
* by the SOC/architecture.
*
* Each GPIO can be an input or output. If an input then its value can
* be read as 0 or 1. If an output then its value can be set to 0 or 1.
* If you try to write an input then the value is undefined. If you try
* to read an output, barring something very unusual, you will get
* back the value of the output that you previously set.
*
* In some cases the operation may fail, for example if the GPIO number
* is out of range, or the GPIO is not available because its pin is
* being used by another function. In that case, functions may return
* an error value of -1.
*/
/**
* Request a gpio. This should be called before any of the other functions
* are used on this gpio.
*
* @param gp GPIO number
* @param label User label for this GPIO
* @return 0 if ok, -1 on error
*/
int gpio_request(unsigned gpio, const char *label);
/**
* Stop using the GPIO. This function should not alter pin configuration.
*
* @param gpio GPIO number
* @return 0 if ok, -1 on error
*/
int gpio_free(unsigned gpio);
/**
* Make a GPIO an input.
*
* @param gpio GPIO number
* @return 0 if ok, -1 on error
*/
int gpio_direction_input(unsigned gpio);
/**
* Make a GPIO an output, and set its value.
*
* @param gpio GPIO number
* @param value GPIO value (0 for low or 1 for high)
* @return 0 if ok, -1 on error
*/
int gpio_direction_output(unsigned gpio, int value);
/**
* Get a GPIO's value. This will work whether the GPIO is an input
* or an output.
*
* @param gpio GPIO number
* @return 0 if low, 1 if high, -1 on error
*/
int gpio_get_value(unsigned gpio);
/**
* Set an output GPIO's value. The GPIO must already be an output or
* this function may have no effect.
*
* @param gpio GPIO number
* @param value GPIO value (0 for low or 1 for high)
* @return 0 if ok, -1 on error
*/
int gpio_set_value(unsigned gpio, int value);
#endif /* _ASM_GENERIC_GPIO_H_ */