100 lines
3.4 KiB
C
100 lines
3.4 KiB
C
#include <errno.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#define GPIO_IFACE_MISSING = -1
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#define GPIO_PIN_EXP_FAIL = -2
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#define GPIO_DIR_CONT_FAIL = -3
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#define GPIO_SWITCH_FAIL = -4
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#define GPIO_PIN_UNX_NF = -5
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#define GPIO_PIN_UNX_FAIL = -6
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#define GPIO_PREFIX "/sys/class/gpio/"
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#define GPIO_EXPORT "export"
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#define GPIO_UNEXPORT "unexport"
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#define MAX_PATHLEN 512
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#define PRINTERRANDRET(mesg, varfmt, var) \
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{ \
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fprintf(stderr, "%s \"%" varfmt "\". %s (%i)\n", mesg, var, strerror(errno), errno); \
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return 1; \
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}
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ssize_t exportPin(signed int pinno);
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ssize_t setPinDirection(signed int pinno, char* value);
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ssize_t setPinValue(signed int pinno, int value);
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int main(int argc, char* argv[])
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{
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int pinno = (argc > 1) ? atoi(argv[1]) : 0;
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bool value = (argc > 2) ? atoi(argv[2]) : 0;
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if (pinno != exportPin(pinno))
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return -1;
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if (pinno != setPinDirection(pinno, "out"))
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return -1;
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if (pinno != setPinValue(pinno, value))
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return -1;
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return 0;
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}
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ssize_t exportPin(signed int pinno)
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{
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if (chdir(GPIO_PREFIX) != 0)
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PRINTERRANDRET("Failed to change directory to", "s", GPIO_PREFIX);
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char buffer[MAX_PATHLEN];
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int fd;
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ssize_t nbytes;
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if ((fd = open(GPIO_EXPORT, O_WRONLY)) < 0)
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PRINTERRANDRET("Failed to open export", "s", GPIO_EXPORT);
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if ((nbytes = snprintf(buffer, MAX_PATHLEN, "%i", pinno)) <= 0)
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PRINTERRANDRET("Couldn't format pin number as string", "i", pinno);
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if (write(fd, buffer, nbytes) != nbytes && errno != EBUSY)
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PRINTERRANDRET("Couldn't write pin number to the exporter", "i", pinno);
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if (close(fd) != 0)
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PRINTERRANDRET("Couldn't close exporter", "i", pinno);
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return pinno;
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}
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ssize_t setPinDirection(signed int pinno, char* value)
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{
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if (chdir(GPIO_PREFIX) != 0)
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PRINTERRANDRET("Failed to change directory to", "s", GPIO_PREFIX);
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char buffer[MAX_PATHLEN];
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int fd;
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ssize_t nbytes;
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if ((nbytes = snprintf(buffer, MAX_PATHLEN, "gpio%i/direction", pinno)) <= 0)
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PRINTERRANDRET("Couldn't format pin path as string", "i", pinno);
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if ((fd = open(buffer, O_WRONLY)) < 0)
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PRINTERRANDRET("Failed to open pin path.", "s", GPIO_EXPORT);
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if (write(fd, value, strlen(value)) != nbytes && errno != EBUSY)
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PRINTERRANDRET("Couldn't write pin direction", "i", pinno);
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if (close(fd) != 0)
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PRINTERRANDRET("Couldn't close pin direction file", "i", pinno);
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return pinno;
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}
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ssize_t setPinValue(signed int pinno, int value)
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{
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if (chdir(GPIO_PREFIX) != 0)
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PRINTERRANDRET("Failed to change directory to", "s", GPIO_PREFIX);
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char buffer[MAX_PATHLEN];
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int fd;
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ssize_t nbytes;
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if ((nbytes = snprintf(buffer, MAX_PATHLEN, "gpio%i/value", pinno)) <= 0)
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PRINTERRANDRET("Couldn't format pin path as string", "i", pinno);
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if ((fd = open(buffer, O_WRONLY)) < 0)
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PRINTERRANDRET("Failed to open pin path.", "s", GPIO_EXPORT);
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if ((nbytes = snprintf(buffer, MAX_PATHLEN, "%i", value)) <= 0)
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PRINTERRANDRET("Couldn't format pin value as string", "i", value);
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if (write(fd, buffer, nbytes) != nbytes && errno != EBUSY)
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PRINTERRANDRET("Couldn't write pin value", "i", pinno);
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if (close(fd) != 0)
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PRINTERRANDRET("Couldn't close pin value file", "i", pinno);
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return pinno;
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}
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