1 // Copyright (c) 2012 The Chromium OS Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include <fcntl.h> 6 #include <linux/fb.h> 7 #include <stdint.h> 8 #include <stdio.h> 9 #include <stdlib.h> 10 #include <sys/mman.h> 11 #include <sys/ioctl.h> 12 #include <unistd.h> 13 14 int main(int argc, char *argv[]) 15 { 16 const char* device_name = "/dev/fb0"; 17 struct fb_var_screeninfo info; 18 uint32_t screen_size = 0; 19 void *ptr = NULL; 20 int fd = -1; 21 FILE *file = NULL; 22 int ret = -1; 23 24 if (argc < 2) { 25 printf("Usage: getfb [filename]\n"); 26 printf("Writes the active framebuffer to output file [filename].\n"); 27 return 0; 28 } 29 30 // Open the file for reading and writing 31 fd = open(device_name, O_RDONLY); 32 if (fd == -1) { 33 fprintf(stderr, "Cannot open framebuffer device %s\n", device_name); 34 goto exit; 35 } 36 printf("The framebuffer device was opened successfully.\n"); 37 38 // Get fixed screen information 39 if (ioctl(fd, FBIOGET_VSCREENINFO, &info) == -1) { 40 fprintf(stderr, "Error reading variable screen information.\n"); 41 goto exit; 42 } 43 44 printf("Framebuffer info: %dx%d, %dbpp\n", info.xres, info.yres, 45 info.bits_per_pixel); 46 47 // Figure out the size of the screen in bytes 48 screen_size = info.xres * info.yres * info.bits_per_pixel / 8; 49 50 // Map the device to memory 51 ptr = mmap(0, screen_size, PROT_READ, MAP_SHARED, fd, 0); 52 if (ptr == MAP_FAILED) { 53 fprintf(stderr, "Error: failed to map framebuffer device to memory.\n"); 54 goto exit; 55 } 56 printf("The framebuffer device was mapped to memory successfully.\n"); 57 58 // Write it to output file. 59 file = fopen(argv[1], "w"); 60 if (!file) { 61 fprintf(stderr, "Could not open file %s for writing.\n", argv[1]); 62 goto exit; 63 } 64 65 if (fwrite(ptr, screen_size, 1, file) < 1) { 66 fprintf(stderr, "Error while writing framebuffer to file.\n"); 67 goto exit; 68 } 69 70 ret = 0; 71 72 exit: 73 if (file) 74 fclose(file); 75 76 if (ptr != MAP_FAILED && ptr) 77 munmap(ptr, screen_size); 78 79 if (fd >= 0) 80 close(fd); 81 82 return ret; 83 } 84
