[microblaze-uclinux] mmap fails when executed on frame buffer device /dev/fb0

["Bergeron, Mario" <Mario.Bergeron@xxxxxxxxx>]

I have a custom frame buffer which I believe is active.  I assume that this frame buffer is actively executing because of the following three observations:

 

1) The /dev/fb0 device exists

 

2) I can see the printk messages appear when the OS boots:

   myfb.c: framebuffer at 0x14000000, mapped to 0x14000000, using 4096K, total 4096K

   myfb.c: mode is 1024x768x32, linelength=4096

   fb0: virtual frame buffer device, using 4096K of video memory, at address 0x14000000

 

3) I can also see the I/O memory space I requested using the "cat /proc/iomem" command:

   > cat /proc/iomem

   14000000-143fffff : My Frame Buffer RAM

   ...

 

 

Now, I want to test the frame buffer.

All of the basic code examples that I have found which communicate with a frame buffer all perform a call to mmap( ).

For example:

   fbdev=open("/dev/fb0", O_RDWR);
   fb=(Uint16 *)mmap(0, 320*240*sizeof(uint16), PROT_WRITE, MAP_SHARED, fbdev, 0);

I always get ENODEV when I call mmap( ) ...

Actually the fb_mmap( ) function declared in fb_ops is not even called.

 

Any ideas on what could be causing this ?

Have I missed something ?

 

Regards,

 

Mario