mirror of
https://github.com/54shady/kernel_drivers_examples.git
synced 2026-01-13 16:02:37 +00:00
97 lines
2.3 KiB
C
97 lines
2.3 KiB
C
#include <stdlib.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <linux/fb.h>
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#include <sys/mman.h>
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#include <sys/ioctl.h>
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#ifdef ANDROID_SYSTEM
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#define DEFAULT_FB_DEVICE "/dev/graphics/fb0"
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#else
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#define DEFAULT_FB_DEVICE "/dev/fb0"
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#endif
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/*
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* Usage:
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* Android:
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* # stop
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* ./lcd_test
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* # start
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* Linux:
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* ./lcd_test
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*/
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int main(int argc, char *argv[])
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{
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int fd = 0;
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struct fb_var_screeninfo vinfo;
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struct fb_fix_screeninfo finfo;
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long int screensize = 0;
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char *fbp = 0;
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int x = 0, y = 0;
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long int location = 0;
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/* Open the file for reading and writing */
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fd = open(DEFAULT_FB_DEVICE, O_RDWR);
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if (fd == -1) {
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perror("Error: cannot open framebuffer device");
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exit(1);
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}
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printf("The framebuffer device was opened successfully.\n");
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/* Get fixed screen information */
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if (ioctl(fd, FBIOGET_FSCREENINFO, &finfo) == -1) {
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perror("Error reading fixed information");
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exit(2);
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}
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/* Get variable screen information */
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if (ioctl(fd, FBIOGET_VSCREENINFO, &vinfo) == -1) {
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perror("Error reading variable information");
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exit(3);
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}
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printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
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/* Figure out the size of the screen in bytes */
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screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
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/* Map the device to memory */
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fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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if (fbp < 0) {
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perror("Error: failed to map framebuffer device to memory");
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exit(4);
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}
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printf("The framebuffer device was mapped to memory successfully.\n");
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/* Figure out where in memory to put the pixel */
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for (y = 0; y < vinfo.yres; y++)
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{
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for (x = 0; x < vinfo.xres; x++)
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{
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location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +
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(y+vinfo.yoffset) * finfo.line_length;
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if (vinfo.bits_per_pixel == 32)
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{
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*(fbp + location) = 100;// Some blue
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*(fbp + location + 1) = 15+(x-100)/2; // A little green
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*(fbp + location + 2) = 200-(y-100)/5;// A lot of red
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*(fbp + location + 3) = 0;// No transparency
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}
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else //assume 16bpp
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{
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int b = 10;
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int g = (x-100)/6; // A little green
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int r = 31-(y-100)/16;// A lot of red
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unsigned short int t = r<<11 | g << 5 | b;
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*((unsigned short int*)(fbp + location)) = t;
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}
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}
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}
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munmap(fbp, screensize);
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close(fd);
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return 0;
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}
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