sysmo-att-ctrl/util/gpio.c

/* GPIO handler routines */

/* (C) 2016 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
 * All Rights Reserved
 *
 * Author: Philipp Maier
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdint.h>
#include <errno.h>
#include <string.h>
#include <osmocom/core/talloc.h>
#include <osmocom/core/utils.h>
#include "gpio.h"

#define SYSFS_EXPORT "/sys/class/gpio/export"
#define SYSFS_UNEXPORT "/sys/class/gpio/unexport"
#define SYSFS_DIRECTION "/sys/class/gpio/gpio%d/direction"
#define SYSFS_VALUE "/sys/class/gpio/gpio%d/value"

/* Open sysfs endpoints and initalize GPIOs */
struct gpio_descr *gpio_open(void *ctx, unsigned int *gpios,
			     unsigned int gpios_len)
{
	int i;
	char buf[255];
	FILE *fd_export = NULL;
	FILE *fd_direction[MAX_GPIOS];
	FILE *fd_value[MAX_GPIOS];
	struct gpio_descr *gd;

	OSMO_ASSERT(gpios);
	OSMO_ASSERT(gpios_len <= MAX_GPIOS);

	/* Export requested GPIOs to userspace */
	fd_export = fopen(SYSFS_EXPORT, "w");
	if (!fd_export) {
		printf("Error: Could not open: %s\n", SYSFS_EXPORT);
		return NULL;
	} else {
		for (i = 0; i < gpios_len; i++) {
			sprintf(buf, "%d", gpios[i]);
			rewind(fd_export);
			fputs(buf, fd_export);
		}
		fclose(fd_export);
		fd_export = NULL;
	}

	/* Open GPIO file descriptors */
	for (i = 0; i < gpios_len; i++) {
		sprintf(buf, SYSFS_DIRECTION, gpios[i]);
		fd_direction[i] = fopen(buf, "w");
		if (!fd_direction[i]) {
			printf("Error: Could not open: %s\n", buf);
			return NULL;
		}

		sprintf(buf, SYSFS_VALUE, gpios[i]);
		fd_value[i] = fopen(buf, "w");
		if (!fd_value[i]) {
			printf("Error: Could not open: %s\n", buf);
			return NULL;
		}
	}

	/* Configure GPIOs as outputs */
	for (i = 0; i < gpios_len; i++) {
		rewind(fd_direction[i]);
		fputs("out", fd_direction[i]);
		fflush(fd_direction[i]);
	}

	/* Generate descriptor struct */
	gd = talloc_zero(ctx, struct gpio_descr);
	memcpy(gd->gpios, gpios, sizeof(gd->gpios));
	gd->gpios_len = gpios_len;
	memcpy(gd->fd_direction, fd_direction, sizeof(gd->fd_direction));
	memcpy(gd->fd_value, fd_value, sizeof(gd->fd_value));

	return gd;
}

/* Close sysfs endpoints and unintialize GPIOs */
void gpio_close(struct gpio_descr *gd)
{
	int i;
	char buf[255];
	FILE *fd_unexport = NULL;

	OSMO_ASSERT(gd);

	/* Close GPIOs file descriptors */
	for (i = 0; i < gd->gpios_len; i++) {
		if (gd->fd_direction[i])
			fclose(gd->fd_direction[i]);
		if (gd->fd_value[i])
			fclose(gd->fd_value[i]);
	}

	/* Remove requested GPIOs from userspace */
	fd_unexport = fopen(SYSFS_UNEXPORT, "w");
	if (fd_unexport) {
		for (i = 0; i < gd->gpios_len; i++) {
			sprintf(buf, "%d", gd->gpios[i]);
			rewind(fd_unexport);
			fputs(buf, fd_unexport);
		}
		fclose(fd_unexport);
	}

	/* Free descriptor struct */
	talloc_free(gd);
}

/* Set GPIO pin status */
void gpio_set(struct gpio_descr *gd, unsigned int gpio, unsigned int state)
{
	OSMO_ASSERT(gd);
	OSMO_ASSERT(gpio < gd->gpios_len);

	rewind(gd->fd_value[gpio]);
	if (state)
		fputs("1", gd->fd_value[gpio]);
	else
		fputs("0", gd->fd_value[gpio]);

	fflush(gd->fd_value[gpio]);
}