| Simon Glass | 9d2cb8e | 2011-10-07 13:53:50 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2011 The Chromium OS Authors. |
| 3 | * See file CREDITS for list of people who contributed to this |
| 4 | * project. |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU General Public License as |
| 8 | * published by the Free Software Foundation; either version 2 of |
| 9 | * the License, or (at your option) any later version. |
| 10 | * |
| 11 | * This program is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | * GNU General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License |
| 17 | * along with this program; if not, write to the Free Software |
| 18 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, |
| 19 | * MA 02111-1307 USA |
| 20 | */ |
| 21 | |
| 22 | /* |
| 23 | * Generic GPIO API for U-Boot |
| 24 | * |
| 25 | * GPIOs are numbered from 0 to GPIO_COUNT-1 which value is defined |
| 26 | * by the SOC/architecture. |
| 27 | * |
| 28 | * Each GPIO can be an input or output. If an input then its value can |
| 29 | * be read as 0 or 1. If an output then its value can be set to 0 or 1. |
| 30 | * If you try to write an input then the value is undefined. If you try |
| 31 | * to read an output, barring something very unusual, you will get |
| 32 | * back the value of the output that you previously set. |
| 33 | * |
| 34 | * In some cases the operation may fail, for example if the GPIO number |
| 35 | * is out of range, or the GPIO is not available because its pin is |
| 36 | * being used by another function. In that case, functions may return |
| 37 | * an error value of -1. |
| 38 | */ |
| 39 | |
| 40 | /** |
| 41 | * Make a GPIO an input. |
| 42 | * |
| 43 | * @param gp GPIO number |
| 44 | * @return 0 if ok, -1 on error |
| 45 | */ |
| 46 | int gpio_direction_input(int gp); |
| 47 | |
| 48 | /** |
| 49 | * Make a GPIO an output, and set its value. |
| 50 | * |
| 51 | * @param gp GPIO number |
| 52 | * @param value GPIO value (0 for low or 1 for high) |
| 53 | * @return 0 if ok, -1 on error |
| 54 | */ |
| 55 | int gpio_direction_output(int gp, int value); |
| 56 | |
| 57 | /** |
| 58 | * Get a GPIO's value. This will work whether the GPIO is an input |
| 59 | * or an output. |
| 60 | * |
| 61 | * @param gp GPIO number |
| 62 | * @return 0 if low, 1 if high, -1 on error |
| 63 | */ |
| 64 | int gpio_get_value(int gp); |
| 65 | |
| 66 | /** |
| 67 | * Set an output GPIO's value. The GPIO must already be an output of |
| 68 | * this function may have no effect. |
| 69 | * |
| 70 | * @param gp GPIO number |
| 71 | * @param value GPIO value (0 for low or 1 for high) |
| 72 | * @return 0 if ok, -1 on error |
| 73 | */ |
| 74 | int gpio_set_value(int gp, int value); |