Linux: framebuffer Test Program

Set FB to 24-Bit mode:

Fbset-FB/dev/fb0-G 800 600 800 24-n

Fill FB with r g B:

Use-FB 255 0 0 // red

Use-FB 0 255 0 // green

...

 

Use-fb.c code:

/* Use-fb.c */

# Include <stdio. h>
# Include <fcntl. h>
# Include <Linux/FB. h>
# Include <sys/Mman. h>
# Include <stdlib. h>

Struct fb_var_screeninfo vinfo;

Int
Main (INT argc, char * argv [])
{
Int fbfd, fbsize, I;
Int red, green, blue;
Unsigned char * fbbuf;

If (argc! = 4 ){
Printf ("Usage: Use-FB red green blue/N ");
Exit (0 );
}
Red = atoi (argv [1]);
Green = atoi (argv [2]);
Blue = atoi (argv [3]);
 
/* Open video memory */
If (fbfd = open ("/dev/fb0", o_rdwr) <0 ){
Exit (1 );
}
/* Get variable display parameters */
If (IOCTL (fbfd, fbioget_vscreeninfo, & vinfo )){
Printf ("Bad vscreeninfo IOCTL/N ");
Exit (2 );
}
/* Size of Frame Buffer */
Fbsize = vinfo. xres * vinfo. yres * (vinfo. bits_per_pixel/8 );
/* Map video memory */
If (fbbuf = MMAP (0, fbsize, prot_read | prot_write,
Map_shared, fbfd, 0) = (void *)-1 ){
Exit (3 );
}
/* Clear the screen */
For (I = 0; I <fbsize; I ++ ){
* (Fbbuf + I ++) = red;
* (Fbbuf + I ++) = green;
* (Fbbuf + I) = blue;
}

Printf ("clear screen with RGB: % S % s/n", argv [1], argv [2], argv [3]);
Munmap (fbbuf, fbsize );
Close (fbfd );
}