2 * Copyright (c) 2011 The Chromium OS Authors.
3 * Copyright (c) 2011, NVIDIA Corp. All rights reserved.
4 * See file CREDITS for list of people who contributed to this
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License as
9 * published by the Free Software Foundation; either version 2 of
10 * the License, or (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
23 #ifndef _ASM_GENERIC_GPIO_H_
24 #define _ASM_GENERIC_GPIO_H_
27 * Generic GPIO API for U-Boot
29 * GPIOs are numbered from 0 to GPIO_COUNT-1 which value is defined
30 * by the SOC/architecture.
32 * Each GPIO can be an input or output. If an input then its value can
33 * be read as 0 or 1. If an output then its value can be set to 0 or 1.
34 * If you try to write an input then the value is undefined. If you try
35 * to read an output, barring something very unusual, you will get
36 * back the value of the output that you previously set.
38 * In some cases the operation may fail, for example if the GPIO number
39 * is out of range, or the GPIO is not available because its pin is
40 * being used by another function. In that case, functions may return
41 * an error value of -1.
45 * Request a gpio. This should be called before any of the other functions
46 * are used on this gpio.
48 * @param gp GPIO number
49 * @param label User label for this GPIO
50 * @return 0 if ok, -1 on error
52 int gpio_request(unsigned gpio, const char *label);
55 * Stop using the GPIO. This function should not alter pin configuration.
57 * @param gpio GPIO number
58 * @return 0 if ok, -1 on error
60 int gpio_free(unsigned gpio);
63 * Make a GPIO an input.
65 * @param gpio GPIO number
66 * @return 0 if ok, -1 on error
68 int gpio_direction_input(unsigned gpio);
71 * Make a GPIO an output, and set its value.
73 * @param gpio GPIO number
74 * @param value GPIO value (0 for low or 1 for high)
75 * @return 0 if ok, -1 on error
77 int gpio_direction_output(unsigned gpio, int value);
80 * Get a GPIO's value. This will work whether the GPIO is an input
83 * @param gpio GPIO number
84 * @return 0 if low, 1 if high, -1 on error
86 int gpio_get_value(unsigned gpio);
89 * Set an output GPIO's value. The GPIO must already be an output or
90 * this function may have no effect.
92 * @param gpio GPIO number
93 * @param value GPIO value (0 for low or 1 for high)
94 * @return 0 if ok, -1 on error
96 int gpio_set_value(unsigned gpio, int value);
97 #endif /* _ASM_GENERIC_GPIO_H_ */