Get/Set screen brightness value on NetBSD

brightness.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/sysctl.h>
#include <inttypes.h>

bool    device_enabled(char *);
char    *find_device(void);
int     get_brightness(char *);
void    set_brightness(char *, unsigned int);
int     usage(void);

bool device_enabled(char *device) {
        size_t size = sizeof(int);
        int buf = 0;
        int res = 0;
        char *name = malloc(BUFSIZ);
        snprintf(name, BUFSIZ, "hw.acpi.%s.bios_switch", device);

        if (sysctlbyname(name, &buf, &size, NULL, 0) == -1) {
                if (errno != ENOENT)
                        fprintf(stderr, "Sysctl failed: %s\n", strerror(errno));
        } else {
                res = buf;
        }

        free(name);
        name = NULL;
        return (res == 1);
}

char *find_device(void) {
        char *vga = "acpivga";
        char *device = NULL;
        device = malloc(BUFSIZ);

        /* get first enabled device */
        for (int num_dev = 0; num_dev < 10; num_dev++) {
                snprintf(device, BUFSIZ, "%s%d", vga, num_dev);
                if (device_enabled(device)) {
                        snprintf(device, BUFSIZ, "acpiout%d", num_dev);
                        return device;
                }
        }

        free(device);
        device = NULL;
        return NULL;
}


int get_brightness(char *device_name) {
        size_t size = sizeof(int);
        int buf = 0;
        int res = 0;
        char *name = malloc(BUFSIZ);
        sprintf(name, "hw.acpi.%s.brightness", device_name);

        if (sysctlbyname(name, &buf, &size, NULL, 0) == -1)
                printf("%s\n", strerror(errno));
        else
                res = buf;

        free(name);
        name = NULL;

        return res;
}

void set_brightness(char *device_name, unsigned int level) {
        size_t size = sizeof(level);
        char *name = malloc(BUFSIZ);
        sprintf(name, "hw.acpi.%s.brightness", device_name);

        if (sysctlbyname(name, NULL, NULL, &level, size) == -1)
                printf("%s\n", strerror(errno));

        free(name);
        name = NULL;
}

int usage(void) {
        const char *progname = getprogname();
        fprintf(stderr, "usage: %s get\n", progname);
        fprintf(stderr, "usage: %s set [0:100]\n", progname);
        return EXIT_FAILURE;
}

int main(int argc, char **argv) {
        if (argc < 2)
                return usage();

        if (strncmp(argv[1], "set", 4) == 0) {
                if (argc != 3)
                        return usage();

                char *buf = strndup(argv[2], BUFSIZ);

                int e;
                intmax_t lval = strtoi(buf, NULL, 10, 0, 100, &e);
                free(buf);
                buf = NULL;

                if (e)
                        return usage();

                char *device = find_device();

                set_brightness(device, lval);

                free(device);
                device = NULL;
        } else if (strncmp(argv[1], "get", 4) == 0) {
                char *device = find_device();

                if (device == NULL) {
                        printf("No devices found.\n");
                        return EXIT_FAILURE;
                } else {
                        printf("current brightness for %s = %u\n",
                                device, get_brightness(device));
                        free(device);
                        device = NULL;
                }
        }
        return EXIT_SUCCESS;
}