rpi_pin.c

/*	Raspberry Pi pin access wrapper
	Copyright (c) 2014 Andrey Chilikin (https://github.com/achilikin)
    
	This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 2 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>

#include "rpi_pin.h"

#if _DEBUG
#define _IFDEB(x) do { x; } while(0)
#else
#define _IFDEB(x)
#endif

static const char *irq_mode[] = { "none\n", "rising\n", "falling\n", "both\n" };

static uint8_t valid_pins_r1[64] =
{
//  pin index
//  0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	1,1,0,0,1,0,0,1,1,1,1,1,0,0,1,1,0,1,1,0,0,1,1,1,1,1,0,0,0,0,0,0
};

static uint8_t valid_pins_r2[64] =
{
//  pin index
//  0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	0,0,1,1,1,0,0,1,1,1,1,1,0,0,1,1,0,1,1,0,0,0,1,1,1,1,0,1,1,1,1,1
};

static uint8_t *pvalid_pins = valid_pins_r2;

static int pin_fds[64];

#define FPIN_EXPORTED  0x0001
#define FPIN_DIR_INPUT 0x0020

static int pin_flags[64];

int rpi_pin_init(int pi_revision)
{
	if (pi_revision == 1)
		pvalid_pins = valid_pins_r1;

	return 0;
}

int rpi_pin_export(uint8_t pin, enum PIN_DIRECTION dir)
{
	FILE *fd;
	char file[128];

	if ((pin > 63) || !pvalid_pins[pin]) {
		_IFDEB(fprintf(stderr, "%s: invalid pin #%u\n", __func__, pin));
		return -1;
	}

	if ((fd = fopen ("/sys/class/gpio/export", "w")) == NULL) {
		_IFDEB(fprintf(stderr, "%s: unable to export pin #%u\n", __func__, pin));
		return -1;
	}
	fprintf(fd, "%d\n", pin);
	fclose(fd);

	sprintf(file, "/sys/class/gpio/gpio%d/direction", pin);
	if ((fd = fopen (file, "w")) == NULL) {
		_IFDEB(fprintf(stderr, "%s: unable to set direction for pin #%u\n", __func__, pin));
		return -1;
	}

	pin_flags[pin] |= FPIN_EXPORTED;
	if (dir == RPI_INPUT)
		pin_flags[pin] |= FPIN_DIR_INPUT;
	fprintf(fd, (dir == RPI_INPUT) ? "in\n" : "out\n");
	fclose(fd);

	sprintf(file, "/sys/class/gpio/gpio%d/value", pin);
	pin_fds[pin] = open(file, O_RDWR);

	return 0;
}

int rpi_pin_set_dir(uint8_t pin, enum PIN_DIRECTION dir)
{
	FILE *fd;
	char file[128];

	if ((pin > 63) || !pvalid_pins[pin])
		return -1;
	
	if (!(pin_flags[pin] & FPIN_EXPORTED))
		return -1;

	sprintf(file, "/sys/class/gpio/gpio%d/direction", pin);
	if ((fd = fopen (file, "w")) == NULL) {
		_IFDEB(fprintf(stderr, "%s: unable to set direction for pin #%u\n", __func__, pin));
		return -1;
	}

	if (dir == RPI_INPUT) {
		pin_flags[pin] |= FPIN_DIR_INPUT;
		fprintf(fd, "in\n");
	}
	else {
		pin_flags[pin] &= ~FPIN_DIR_INPUT;
		fprintf(fd, "out\n");
	}
	fclose(fd);

	return 0;
}

// read input value:
//	0 - low
//	1 - high
// -1 - error
int rpi_pin_get(uint8_t pin)
{
	// this will check pin validity as well
	int fd = rpi_pin_fd(pin);

	if (fd < 0)
		return -1;

	if (!(pin_flags[pin] & FPIN_DIR_INPUT))
		return -1;

	return rpi_pin_poll_clear(fd);
}

// set output value
int rpi_pin_set(uint8_t pin, uint8_t value)
{
	// this will check pin validity as well
	int fd = rpi_pin_fd(pin);

	if (fd < 0)
		return -1;

	if (pin_flags[pin] & FPIN_DIR_INPUT)
		return -1;
	
	lseek(fd, 0, SEEK_SET);
	return (write(fd, value ? "1" : "0", 1) == 1) ? 0 : -1;
}

int rpi_pin_unexport(uint8_t pin)
{
	FILE *fd;

	if ((pin > 63) || !pvalid_pins[pin])
		return -1;

	if (!(pin_flags[pin] & FPIN_EXPORTED))
		return 0;

	if ((fd = fopen ("/sys/class/gpio/unexport", "w")) == NULL) {
		_IFDEB(fprintf(stderr, "%s: unable to unexport pin #%u\n", __func__, pin));
		return -1;
	}
	fprintf(fd, "%d\n", pin);
	fclose(fd);

	pin_flags[pin] = 0;
	close(pin_fds[pin]);
	pin_fds[pin] = -1;

	return 0;
}

// functions for pin change of value edge detection support using poll()

// returns pin's file descriptor
int rpi_pin_fd(uint8_t pin)
{
	if ((pin > 63) || !pvalid_pins[pin])
		return -1;

	if (pin_flags[pin] & FPIN_EXPORTED)
		return pin_fds[pin];

	return -1;
}

// enables POLLPRI on edge detection, pin must be in INPUT mode
// returns file descriptor to be used with poll() or -1 as error
int rpi_pin_poll_enable(uint8_t pin, enum PIN_EDGE_MODE mode)
{
	FILE *fd;
	char file[128];

	if ((pin > 63) || !pvalid_pins[pin])
		return -1;

	if (!(pin_flags[pin] & FPIN_EXPORTED))
		rpi_pin_export(pin, RPI_INPUT);

	if (pin_fds[pin] < 0)
		return -1;

	sprintf(file, "/sys/class/gpio/gpio%d/edge", pin);
	if ((fd = fopen (file, "w")) == NULL) {
		_IFDEB(fprintf(stderr, "%s: setting edge detection failed for pin #%u: %s\n", __func__, pin));
		return -1;
	}

	fputs(irq_mode[mode], fd);
	fclose(fd);

	rpi_pin_poll_clear(pin_fds[pin]);

	return pin_fds[pin];
}