/*==================== basic IO access : port_write_then_read.c ===============

  PURPOSE - show port write and read.
          - usage ./port_write_then_read port_num value
*/
#include <iostream.h>
#include <iomanip.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/io.h>

int main( int argc, char *argv[] )
{
        if ( argc != 3 ) {
                cerr << "usage: " << argv[ 0 ] << " port_num write_value\n"
                     << "Both numbers are in hexadecimal\n";
                exit( 1 );
        }
  
        // Output a byte to a port:
        int  port_num = strtol( argv[ 1 ], NULL, 16 ) & 0x3ff;
        char value    = strtol( argv[ 2 ], NULL, 16 ) & 0xff;
        outb( value, port_num );
        
        // Read the data byte port:
        cout << showbase << "Wrote " << hex << value << " to port "
             << port_num << ", read back " << ( unsigned ) inb( port_num )
             << endl;
        exit( 0 ); 
}