The Linux kernel GPIO api operates with chips, lines, handles, and events. The chip and line structures represent info about gpio chips, and gpio lines, respectively. They are used to e.g. lookup a line with a certain name, and/or line flags. The handle structure is used to "obtain" a handle to one or more gpio lines on a chip. Until the file descriptor in this handle is closed, the gpio lines cannot be used by others. The same file descriptor is used when setting or getting the line values (one can also set the initial value when obtaining handles for output lines). The event structure is used to get a file descriptor that can be used with select/poll to wait for changes in line levels. This commit add simple support for setting and getting the value for a single gpio line. It does so by obtaining a line handle to get/set the value, and then release the handle immediately again. Functionality that could be implemented, but is postponed until the need arises includes: * looking up a gpio line by its name * setting/getting multiple gpio lines with a single function * waiting for events * holding on to handles Some of the above probably require adding structures to represent gpio lines and events, while handles should be private to the class. --- Changes since v1: * added gpiochip info and corresponding getters * changed "line" to "line_num" a few places Changes since RFC: * added gpio.h to ell.h * changed copyright to Geanix * open gpiochip in l_gpio_chip_new() * open gpiochip read-only * added input checks * clear ioctl structs with memset instead of = {0} * reorder error-paths Makefile.am | 6 +- ell/ell.h | 1 + ell/ell.sym | 7 +++ ell/gpio.c | 175 ++++++++++++++++++++++++++++++++++++++++++++++++++++ ell/gpio.h | 49 +++++++++++++++ 5 files changed, 236 insertions(+), 2 deletions(-) create mode 100644 ell/gpio.c create mode 100644 ell/gpio.h diff --git a/Makefile.am b/Makefile.am index 8401972..0ecb9a1 100644 --- a/Makefile.am +++ b/Makefile.am @@ -51,7 +51,8 @@ pkginclude_HEADERS = ell/ell.h \ ell/dhcp.h \ ell/cert.h \ ell/ecc.h \ - ell/ecdh.h + ell/ecdh.h \ + ell/gpio.h lib_LTLIBRARIES = ell/libell.la @@ -119,7 +120,8 @@ ell_libell_la_SOURCES = $(linux_headers) \ ell/ecc.h \ ell/ecc-external.c \ ell/ecc.c \ - ell/ecdh.c + ell/ecdh.c \ + ell/gpio.c ell_libell_la_LDFLAGS = -no-undefined \ -Wl,--version-script=$(top_srcdir)/ell/ell.sym \ diff --git a/ell/ell.h b/ell/ell.h index aab6417..fb1dd79 100644 --- a/ell/ell.h +++ b/ell/ell.h @@ -59,3 +59,4 @@ #include <ell/cert.h> #include <ell/ecc.h> #include <ell/ecdh.h> +#include <ell/gpio.h> diff --git a/ell/ell.sym b/ell/ell.sym index 841bc49..793e4c3 100644 --- a/ell/ell.sym +++ b/ell/ell.sym @@ -463,6 +463,13 @@ global: /* ecdh */ l_ecdh_generate_key_pair; l_ecdh_generate_shared_secret; + /* gpio */ + l_gpio_chip_new; + l_gpio_chip_free; + l_gpio_chip_get_label; + l_gpio_chip_get_num_lines; + l_gpio_chip_get_line_value; + l_gpio_chip_set_line_value; local: *; }; diff --git a/ell/gpio.c b/ell/gpio.c new file mode 100644 index 0000000..83032f9 --- /dev/null +++ b/ell/gpio.c @@ -0,0 +1,175 @@ +/* + * + * Embedded Linux library + * + * Copyright (C) 2018 Geanix. All rights reserved. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + * + */ + +#ifdef HAVE_CONFIG_H +#include <config.h> +#endif + +#include <unistd.h> +#include <sys/ioctl.h> +#include <fcntl.h> +#include <linux/gpio.h> + +#include "util.h" +#include "gpio.h" +#include "private.h" + +struct l_gpio_chip { + int fd; + char *label; + uint32_t num_lines; +}; + +LIB_EXPORT struct l_gpio_chip *l_gpio_chip_new(const char *chip_name) +{ + struct l_gpio_chip *chip; + struct gpiochip_info info; + char *path; + int ret; + + if (!chip_name) + return NULL; + + chip = l_new(struct l_gpio_chip, 1); + + path = l_strdup_printf("/dev/%s", chip_name); + chip->fd = open(path, O_RDONLY | O_CLOEXEC); + l_free(path); + + if (chip->fd < 0) { + l_free(chip); + return NULL; + } + + memset(&info, 0, sizeof(info)); + + ret = ioctl(chip->fd, GPIO_GET_CHIPINFO_IOCTL, &info); + if (ret < 0) { + l_free(chip); + return NULL; + } + + if (info.label) + chip->label = l_strndup(info.label, sizeof(info.label)); + + chip->num_lines = info.lines; + + return chip; +} + +LIB_EXPORT void l_gpio_chip_free(struct l_gpio_chip *chip) +{ + if (!chip) + return; + + if (chip->fd >= 0) + close(chip->fd); + + l_free(chip->label); + l_free(chip); +} + +LIB_EXPORT const char *l_gpio_chip_get_label(struct l_gpio_chip *chip) +{ + if (!chip) + return NULL; + + return chip->label; +} + +LIB_EXPORT uint32_t l_gpio_chip_get_num_lines(struct l_gpio_chip *chip) +{ + if (!chip) + return 0; + + return chip->num_lines; +} + +LIB_EXPORT bool l_gpio_chip_get_line_value(struct l_gpio_chip *chip, + uint32_t line_num, bool *value) +{ + struct gpiohandle_request req; + struct gpiohandle_data data; + int ret; + + if (!chip) + return false; + + if (line_num >= chip->num_lines) + return false; + + if (chip->fd < 0) + return false; + + memset(&req, 0, sizeof(req)); + req.lineoffsets[0] = line_num; + req.lines = 1; + req.flags = GPIOHANDLE_REQUEST_INPUT; + + ret = ioctl(chip->fd, GPIO_GET_LINEHANDLE_IOCTL, &req); + if (ret < 0 || req.fd <= 0) + return false; + + memset(&data, 0, sizeof(data)); + + ret = ioctl(req.fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, &data); + + close(req.fd); + + if (ret < 0) + return false; + + if (value) + *value = !!data.values[0]; + + return true; +} + +LIB_EXPORT bool l_gpio_chip_set_line_value(struct l_gpio_chip *chip, + uint32_t line_num, bool value) +{ + struct gpiohandle_request req; + int ret; + + if (!chip) + return false; + + if (line_num >= chip->num_lines) + return false; + + if (chip->fd < 0) + return false; + + memset(&req, 0, sizeof(req)); + req.lineoffsets[0] = line_num; + req.lines = 1; + req.flags = GPIOHANDLE_REQUEST_OUTPUT; + req.default_values[0] = value; + + ret = ioctl(chip->fd, GPIO_GET_LINEHANDLE_IOCTL, &req); + if (ret < 0 || req.fd <= 0) + return false; + + close(req.fd); + + return true; +} diff --git a/ell/gpio.h b/ell/gpio.h new file mode 100644 index 0000000..9f4ae6a --- /dev/null +++ b/ell/gpio.h @@ -0,0 +1,49 @@ +/* + * + * Embedded Linux library + * + * Copyright (C) 2011-2018 Intel Corporation. All rights reserved. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + * + */ + +#ifndef __ELL_GPIO_H +#define __ELL_GPIO_H + +#include <stdint.h> +#include <stdbool.h> + +#ifdef __cplusplus +extern "C" { +#endif + +struct l_gpio_chip; + +struct l_gpio_chip *l_gpio_chip_new(const char *chip_name); +void l_gpio_chip_free(struct l_gpio_chip *chip); + +const char *l_gpio_chip_get_label(struct l_gpio_chip *chip); +uint32_t l_gpio_chip_get_num_lines(struct l_gpio_chip *chip); +bool l_gpio_chip_get_line_value(struct l_gpio_chip *chip, uint32_t line_num, + bool *value); +bool l_gpio_chip_set_line_value(struct l_gpio_chip *chip, uint32_t line_num, + bool value); + +#ifdef __cplusplus +} +#endif + +#endif /* __ELL_GPIO_H */ -- 2.20.0