i.MX6: fb2 Framebuffer issue

Showing results for 
Search instead for 
Did you mean: 

i.MX6: fb2 Framebuffer issue

Contributor I

Hi ,  

Imx6 has 6 frame buffers - fb0 to fb5. We are able to get fb0 and fb1 working using the standard fb test program. Also, we are able to get fb0 and fb1 simultaneously working with alpha values set.

But, we are unable to get any other fbs working. We understand that fb2 is also BG like fb0. All the IOCTLs seem to work well, but we are unable to see any visual display for fb.

We have allocated vram for fb2, tried setting vscreen info in code corresponding to 800 * 480 and used vsync ioctl too. Setting vscreeninfo corresponding to fb0 - 1024 * 768 also does not solve the issue. But we are unable to see any output on screen, though there is no error. We have not got the LCD up for our board and hence trying to test the same using monitor currently.

Find code snippet below used and also the setenv values:  

bootargs :console=tty1 console=ttymxc1,115200 video=mxcfb0:dev=hdmi,1280x720M@60,if=RGB24 root=/dev/mmcblk0p2 rootfs=ext4 rw rootwait vmalloc=192M vram=1:3M,2:3M,3:3M,4:3M,5:3M  


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

int main()
        int fbfd = 0;
        struct fb_var_screeninfo vinfo;
        struct fb_fix_screeninfo finfo;
        long int screensize = 0;
        char *fbp = 0;
        int x = 0, y = 0;

        long int location = 0;
        int rc,errno;
        /* Open the file for reading and writing */
        fbfd = open("/dev/fb2", O_RDWR);
        if (!fbfd) {
                printf("Error: cannot open framebuffer device./n");

        printf("The framebuffer device was opened successfully./n");

        /* Get fixed screen information */

          if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {

                printf("Error reading fixed information./n");



         /* Get variable screen information */
        if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
                printf("Error reading variable information./n");

       /* Figure out the size of the screen in bytes */
        screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
        struct fb_var_screeninfo * screenInfo =  &vinfo;

        rc = ioctl(fbfd, FBIOBLANK, FB_BLANK_UNBLANK);
        if (rc)
         printf("Error setting size on device /dev/fb1, errno %d", errno);

        screenInfo->bits_per_pixel = 16;
        screenInfo->xres = 1280;
        screenInfo->yres = 720;
        screenInfo->xres_virtual = screenInfo->xres;
        screenInfo->yres_virtual = screenInfo->yres;
        screenInfo->xoffset = 0;
        screenInfo->yoffset = 0;

        rc = ioctl(fbfd, FBIOPUT_VSCREENINFO, screenInfo);
        screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
        printf("%dx%d, %dbpp\n screensize=%ld", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel,screensize);

        ioctl(fbfd, MXCFB_WAIT_FOR_VSYNC, 0);

        /* Map the device to memory */
        fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,
                fbfd, 0);      
        if ((int)fbp == -1) { printf("Error: failed to map  framebuffer device to memory./n");

        printf("The framebuffer device was mapped to memory successfully./n");


        for (x=50000; x < 400000;x++)      { 

         /* Figure out where in memory to put the pixel */

         location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +(y+vinfo.yoffset) * finfo.line_length;

        *(fbp + x) = 0xffffff; }

        munmap(fbp, screensize);
        return 0;

Is there any specific settings that we need to use to get fb2 working?
Also for our application use case, we need 3 layers - one of the menu, one for display for video like map and one more layer to show directions. So we need to simultaneously use 3 fbs.
Please suggest which fb combination to use and setting to be done for the same




Tags (1)
2 Replies

Contributor II

On i.mx6, ONLY the primary fb(fb0) is on, all other fbs are off. It needs to unblank the related fb by the following command:

echo 0 > /sys/class/graphics/fb2/blank.

For three layers, the hardware IPU by default doesn't support it. It can only support 2-layer(BG, FG). You can use ipu device interface to do combination, or use GPU to do combination.

0 Kudos

Contributor I


  you are several steps ahead of me, but sound like you go something working I need.

I only need the fb0 with a single alpha blended overlay (which I assume is fb1). You say you have that working. I have a similar set of code as your example but have not had the over lay display. Hints ? I would guess I have an setup issue or am not toggling alpha correctly.


0 Kudos