//-------------------------------------------------------------------
//	instatus.cpp
//
//	This program produces a visualization for the state of the 
//	SVGA's Input Status Register 1 by continuously drawing its 
//	volatile contents to successive pixel-locations within the 
//	graphics display memory (using a 1024x768 256-color mode); 
//      the program terminates when the screen is completely full.
//
//	 compile using:  $ g++ instatus.cpp int86.cpp -o instatus
//
//	programmer: ALLAN CRUSE
//	written on: 13 SEP 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for lseek()  
#include <sys/mman.h>	// for mmap()
#include <sys/io.h>	// for inb()
#include "int86.h"	// for init8086(), int86()

#define VRAM_BASE	0xA0000000
#define INPUT_STATUS_1	0x03DA

unsigned char	*vram = (unsigned char*)VRAM_BASE;
int vesa_mode = 0x4105, hres = 1024, vres = 768;
struct vm86plus_struct	vm;

int main( int argc, char **argv )
{
	// memory-map the graphics display-memory into user-space
	int	vd = open( "/dev/vram", O_RDWR );
	if ( vd < 0 ) { perror( "/dev/vram" ); exit(1); }
	int	size = lseek( vd, 0, SEEK_END );
	int	prot = PROT_READ | PROT_WRITE;
	int	flag = MAP_FIXED | MAP_SHARED;
	void	*mm = (void*)VRAM_BASE;
	if ( mmap( mm, size, prot, flag, vd, 0 ) == MAP_FAILED )
		{ perror( "mmap" ); exit(1); }
	
	// enter graphics mode
	init8086();			// enable BIOS and I/O access
	vm.regs.eax = 0x4F02;		// VESA Set Display Mode
	vm.regs.ebx = vesa_mode;	// Specify Mode ID
	int86( 0x10, vm );		// invoke BIOS service

	// fill the visible screen with bytes from INPUT_STATUS_1
	for (int pel = 0; pel < hres * vres; pel++)
		vram[ pel ] = inb( INPUT_STATUS_1 );
	getchar();			// await <ENTER>-key

	// leave graphics mode
	vm.regs.eax = 0x0003;		// VGA Set Display Mode 3
	int86( 0x10, vm );		// invoke BIOS service
	printf( "\ndone\n\n" );		// show termination message
}