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