gpio-utils.c

/*
 * GPIO tools - helpers library for the GPIO tools
 *
 * Copyright (C) 2015 Linus Walleij
 * Copyright (C) 2016 Bamvor Jian Zhang
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <getopt.h>
#include <sys/ioctl.h>
#include <linux/gpio.h>
#include "gpio-utils.h"

#define COMSUMER "gpio-utils"

/**
 * doc: Operation of gpio
 *
 * Provide the api of gpiochip for chardev interface. There are two
 * types of api.  The first one provide as same function as each
 * ioctl, including request and release for lines of gpio, read/write
 * the value of gpio. If the user want to do lots of read and write of
 * lines of gpio, user should use this type of api.
 *
 * The second one provide the easy to use api for user. Each of the
 * following api will request gpio lines, do the operation and then
 * release these lines.
 */
/**
 * gpiotools_request_linehandle() - request gpio lines in a gpiochip
 * @device_name:	The name of gpiochip without prefix "/dev/",
 *			such as "gpiochip0"
 * @lines:		An array desired lines, specified by offset
 *			index for the associated GPIO device.
 * @nline:		The number of lines to request.
 * @flag:		The new flag for requsted gpio. Reference
 *			"linux/gpio.h" for the meaning of flag.
 * @data:		Default value will be set to gpio when flag is
 *			GPIOHANDLE_REQUEST_OUTPUT.
 * @consumer_label:	The name of consumer, such as "sysfs",
 *			"powerkey". This is useful for other users to
 *			know who is using.
 *
 * Request gpio lines through the ioctl provided by chardev. User
 * could call gpiotools_set_values() and gpiotools_get_values() to
 * read and write respectively through the returned fd. Call
 * gpiotools_release_linehandle() to release these lines after that.
 *
 * Return:		On success return the fd;
 *			On failure return the errno.
 */
int gpiotools_request_linehandle(const char *device_name, unsigned int *lines,
				 unsigned int nlines, unsigned int flag,
				 struct gpiohandle_data *data,
				 const char *consumer_label)
{
	struct gpiohandle_request req;
	char *chrdev_name;
	int fd;
	int i;
	int ret;

	ret = asprintf(&chrdev_name, "/dev/%s", device_name);
	if (ret < 0)
		return -ENOMEM;

	fd = open(chrdev_name, 0);
	if (fd == -1) {
		ret = -errno;
		fprintf(stderr, "Failed to open %s, %s\n",
			chrdev_name, strerror(errno));
		goto exit_close_error;
	}

	for (i = 0; i < nlines; i++)
		req.lineoffsets[i] = lines[i];

	req.flags = flag;
	strcpy(req.consumer_label, consumer_label);
	req.lines = nlines;
	if (flag & GPIOHANDLE_REQUEST_OUTPUT)
		memcpy(req.default_values, data, sizeof(req.default_values));

	ret = ioctl(fd, GPIO_GET_LINEHANDLE_IOCTL, &req);
	if (ret == -1) {
		ret = -errno;
		fprintf(stderr, "Failed to issue %s (%d), %s\n",
			"GPIO_GET_LINEHANDLE_IOCTL", ret, strerror(errno));
	}

exit_close_error:
	if (close(fd) == -1)
		perror("Failed to close GPIO character device file");
	free(chrdev_name);
	return ret < 0 ? ret : req.fd;
}
/**
 * gpiotools_set_values(): Set the value of gpio(s)
 * @fd:			The fd returned by
 *			gpiotools_request_linehandle().
 * @data:		The array of values want to set.
 *
 * Return:		On success return 0;
 *			On failure return the errno.
 */
int gpiotools_set_values(const int fd, struct gpiohandle_data *data)
{
	int ret;

	ret = ioctl(fd, GPIOHANDLE_SET_LINE_VALUES_IOCTL, data);
	if (ret == -1) {
		ret = -errno;
		fprintf(stderr, "Failed to issue %s (%d), %s\n",
			"GPIOHANDLE_SET_LINE_VALUES_IOCTL", ret,
			strerror(errno));
	}

	return ret;
}

/**
 * gpiotools_get_values(): Get the value of gpio(s)
 * @fd:			The fd returned by
 *			gpiotools_request_linehandle().
 * @data:		The array of values get from hardware.
 *
 * Return:		On success return 0;
 *			On failure return the errno.
 */
int gpiotools_get_values(const int fd, struct gpiohandle_data *data)
{
	int ret;

	ret = ioctl(fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, data);
	if (ret == -1) {
		ret = -errno;
		fprintf(stderr, "Failed to issue %s (%d), %s\n",
			"GPIOHANDLE_GET_LINE_VALUES_IOCTL", ret,
			strerror(errno));
	}

	return ret;
}

/**
 * gpiotools_release_linehandle(): Release the line(s) of gpiochip
 * @fd:			The fd returned by
 *			gpiotools_request_linehandle().
 *
 * Return:		On success return 0;
 *			On failure return the errno.
 */
int gpiotools_release_linehandle(const int fd)
{
	int ret;

	ret = close(fd);
	if (ret == -1) {
		perror("Failed to close GPIO LINEHANDLE device file");
		ret = -errno;
	}

	return ret;
}

/**
 * gpiotools_get(): Get value from specific line
 * @device_name:	The name of gpiochip without prefix "/dev/",
 *			such as "gpiochip0"
 * @line:		number of line, such as 2.
 *
 * Return:		On success return 0;
 *			On failure return the errno.
 */
int gpiotools_get(const char *device_name, unsigned int line)
{
	struct gpiohandle_data data;
	unsigned int lines[] = {line};

	gpiotools_gets(device_name, lines, 1, &data);
	return data.values[0];
}


/**
 * gpiotools_gets(): Get values from specific lines.
 * @device_name:	The name of gpiochip without prefix "/dev/",
 *			such as "gpiochip0".
 * @lines:		An array desired lines, specified by offset
 *			index for the associated GPIO device.
 * @nline:		The number of lines to request.
 * @data:		The array of values get from gpiochip.
 *
 * Return:		On success return 0;
 *			On failure return the errno.
 */
int gpiotools_gets(const char *device_name, unsigned int *lines,
		   unsigned int nlines, struct gpiohandle_data *data)
{
	int fd;
	int ret;
	int ret_close;

	ret = gpiotools_request_linehandle(device_name, lines, nlines,
					   GPIOHANDLE_REQUEST_INPUT, data,
					   COMSUMER);
	if (ret < 0)
		return ret;

	fd = ret;
	ret = gpiotools_get_values(fd, data);
	ret_close = gpiotools_release_linehandle(fd);
	return ret < 0 ? ret : ret_close;
}

/**
 * gpiotools_set(): Set value to specific line
 * @device_name:	The name of gpiochip without prefix "/dev/",
 *			such as "gpiochip0"
 * @line:		number of line, such as 2.
 * @value:		The value of gpio, must be 0(low) or 1(high).
 *
 * Return:		On success return 0;
 *			On failure return the errno.
 */
int gpiotools_set(const char *device_name, unsigned int line,
		  unsigned int value)
{
	struct gpiohandle_data data;
	unsigned int lines[] = {line};

	data.values[0] = value;
	return gpiotools_sets(device_name, lines, 1, &data);
}

/**
 * gpiotools_sets(): Set values to specific lines.
 * @device_name:	The name of gpiochip without prefix "/dev/",
 *			such as "gpiochip0".
 * @lines:		An array desired lines, specified by offset
 *			index for the associated GPIO device.
 * @nline:		The number of lines to request.
 * @data:		The array of values set to gpiochip, must be
 *			0(low) or 1(high).
 *
 * Return:		On success return 0;
 *			On failure return the errno.
 */
int gpiotools_sets(const char *device_name, unsigned int *lines,
		   unsigned int nlines, struct gpiohandle_data *data)
{
	int ret;

	ret = gpiotools_request_linehandle(device_name, lines, nlines,
					   GPIOHANDLE_REQUEST_OUTPUT, data,
					   COMSUMER);
	if (ret < 0)
		return ret;

	return gpiotools_release_linehandle(ret);
}