fbget.c

/*
 * MIT License
 *
 * Copyright (c) 2023 @cleanbaja
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/fb.h>

#define DEFAULT_FB_PATH "/dev/fb0"

int main(int argc, char** argv) {
    char *fb_path = DEFAULT_FB_PATH;

    if (argc > 1)
        fb_path = argv[1];

    int fb = open(fb_path, O_RDWR);
    if (fb < 0) {
        perror("open");
	return 1;
    }

    struct fb_var_screeninfo vinfo;
    if (ioctl(fb, FBIOGET_VSCREENINFO, &vinfo) < 0) {
        perror("ioctl");
	return 1;
    }

    printf("%ux%ux%u\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);

    close(fb);
    return 0;
}