1 /* 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 5 * project. 6 * 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. 11 * 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. 16 * 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, 20 * MA 02111-1307 USA 21 */ 22 23 #ifndef _ASM_GENERIC_GPIO_H_ 24 #define _ASM_GENERIC_GPIO_H_ 25 26 /* 27 * Generic GPIO API for U-Boot 28 * 29 * GPIOs are numbered from 0 to GPIO_COUNT-1 which value is defined 30 * by the SOC/architecture. 31 * 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. 37 * 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. 42 */ 43 44 /** 45 * Request ownership of a GPIO. 46 * 47 * @param gpio GPIO number 48 * @param label Name given to the GPIO 49 * @return 0 if ok, -1 on error 50 */ 51 int gpio_request(unsigned gpio, const char *label); 52 53 /** 54 * Stop using the GPIO. This function should not alter pin configuration. 55 * 56 * @param gpio GPIO number 57 * @return 0 if ok, -1 on error 58 */ 59 int gpio_free(unsigned gpio); 60 61 /** 62 * Make a GPIO an input. 63 * 64 * @param gpio GPIO number 65 * @return 0 if ok, -1 on error 66 */ 67 int gpio_direction_input(unsigned gpio); 68 69 /** 70 * Make a GPIO an output, and set its value. 71 * 72 * @param gpio GPIO number 73 * @param value GPIO value (0 for low or 1 for high) 74 * @return 0 if ok, -1 on error 75 */ 76 int gpio_direction_output(unsigned gpio, int value); 77 78 /** 79 * Get a GPIO's value. This will work whether the GPIO is an input 80 * or an output. 81 * 82 * @param gpio GPIO number 83 * @return 0 if low, 1 if high, -1 on error 84 */ 85 int gpio_get_value(unsigned gpio); 86 87 /** 88 * Set an output GPIO's value. The GPIO must already be an output or 89 * this function may have no effect. 90 * 91 * @param gpio GPIO number 92 * @param value GPIO value (0 for low or 1 for high) 93 * @return 0 if ok, -1 on error 94 */ 95 int gpio_set_value(unsigned gpio, int value); 96 97 /** 98 * Request a gpio. This should be called before any of the other functions 99 * are used on this gpio. 100 * 101 * @param gp GPIO number 102 * @param label User label for this GPIO 103 * @return 0 if ok, -1 on error 104 */ 105 int gpio_request(unsigned gpio, const char *label); 106 #endif /* _ASM_GENERIC_GPIO_H_ */ 107