//-------------------------------------------------------------------
//	nicstudy.cpp	 (An enhancement of our 'nicregs.cpp' deno)
//
//	This program utilizes our 'user8139.c' device-driver to map 
//	the RealTek 8139 network interface registers to user-space; 
//	also to do read(), write(), and lseek() on a kernel buffer.
//
//	It is assumed that the System Administrator has created the
//	required character-mode device-node in the '/dev' directory
//	before the user attempts to execute this program:
//
//			root#  mknod /dev/nic c 98 0
//			root#  chmod a+rw /dev/nic
//
//	programmer: ALLAN CRUSE
//	written on: 06 APR 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <sys/mman.h>	// for mmap(), munmap()
#include <string.h>	// for memset(), strncpy()
#include <unistd.h>	// for sleep()

char nicname[] = "/dev/nic";

void show_nic_registers( void *vm )
{
	// display the contents of io-memory in hexadecimal format
	printf( "\n\nRealTek 8139 Registers mapped at %p \n", vm );	
	unsigned long 	*lp = (unsigned long *)vm;
	for (int i = 0; i < 64; i++)
		{
		if ( ( i % 8 ) == 0 ) printf( "\n%02X: ", i*4 ); 
		printf( "%08lX ", lp[ i ] );
		}
	printf( "\n" );
}

int main( int argc, char **argv )
{
	// open the device-file
	int	fd = open( nicname, O_RDWR );
	if ( fd < 0 ) { perror( nicname ); exit(1); }

	// map the device's io-memory to user-space
	int	prot = PROT_READ | PROT_WRITE;
	int	flag = MAP_SHARED;
	int	size = 0x1000;
	int	base = 0;  
	void	*vm = mmap( NULL, size, prot, flag, fd, base );
	if ( vm == MAP_FAILED ) { perror( "mmap" ); exit(1); }
	
	// display the contents of io-memory in hexadecimal format
	show_nic_registers( vm );

	//-----------------------------------------
	// OK, now let's study packet transmission
	//-----------------------------------------
	int	io = (int)vm;
	unsigned char	*RTCommand = (unsigned char *)(io+0x37);
	unsigned long	*TxStatus0 = (unsigned long *)(io+0x10);
	unsigned long	*Tx_Config = (unsigned long *)(io+0x40);

	// reset the network controller
	*RTCommand = 0x10;
	sleep(1);

	// place our network packet into the kernel buffer area
	char	packet[ 64 ] = {0};
	memset( packet+0, 0xFF, 6 );	// broadcast address
	memset( packet+6, 0x00, 6 );	// unspecified source
	strncpy( packet+16, "Hello", 5 ); 
	lseek( fd, 0, SEEK_SET );	// point to TxBuffer0
	int 	nbytes = write( fd, packet, sizeof(packet) );	
	printf( "\n%d bytes written to kernel buffer \n", nbytes );

	// now try to transmit the packet
	*RTCommand = 0x04;	// enable TX
	*Tx_Config = 0;		// configure TX
	*TxStatus0 = 64;	// transmit TxBuffer0
	
	sleep( 1 );	

	show_nic_registers( vm );
}