I have an SSD 1306 OLED display on my Beaglebone that is configured as a framebuffer in LInux (3.8.13).
I want to use mmap to get its framebuffer so I can draw on it. The mmap call does return a pointer, but subsequent operations will segfault.
This is the C code:
`
#include <stdio.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/fb.h>
#include <sys/ioctl.h>
#include <wakkomononormalh.h>
#include <string.h>
#include <time.h>static char b[1024]; /* Local image buffer */
static struct timespec displaydelay;int main()
{
struct fb_fix_screeninfo fb_fixed_info; /* Framebuffer information */int fbfd = 0;
char *fbp = 0;//Open the file for reading and writing
fbfd = open(“/dev/fb0”, O_RDWR);//Map the device to memory
fbp = (char *)mmap(0, fb_fixed_info.smem_len, PROT_READ | PROT_WRITE, MAP_SHARED,
fbfd, 0);if ((int)fbp == -1) { printf(“Error: failed to map framebuffer device to memory./n”);
return 4;
}printf(“The framebuffer device was mapped to memory successfully./n”);
// Clear screen
memset(b,0,fb_fixed_info.smem_len);
memcpy(fbp,b,screensize);`
The code fails at memcpy. I knew I would have a learning curve, but I have been in circles on this. I thought I dodged a bullet not having to write kernel drivers for my project, but…
Thanks.