pic.c

一个操作系统的源代码

/** pic.c
 **
 ** Original Author: Kasper Verdich Lund
 ** Date: 10/11/99
 **
 ** Description:
 ** Programable Interrupt Controller functions
 **
 ** This program is free software, you can redistribute it and/or
 ** modify it under the terms of the GNU General Public License
 ** as published by the Free Software Foundation; either version
 ** 2 of the License, or (at your option) any later version.
 **
 ** This program is distributed in the hope that it will be
 ** useful, but WITHOUT ANY WARRANTY; without even the implied
 ** warranty or MERCHANTABILITY or FITNESS FOR A PARTICULAR
 ** PURPOSE.  See the GNU General Public License for more
 ** details.
 **
 ** You should have received a copy of the GNU General Public
 ** License along with this program; if not, write to the
 ** Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 ** Boston, MA 02111-1307 USA
 **
 *********************************************************Apostle OS**/

#include <pic.h>
#include <io.h>
#include <types.h>

/* 16-bits of IRQ masking */
static word IRQmask;

/* reprogramPIC() is based on the Linux source code
 * could probably be done in a nicer more general way */
void reprogramPIC(void)
{
  /* move irqs to 0x20-0x2F 
   * this makes room for the exceptions 0x0-0x1F */
  outb(0x20,0x11); 
  io_wait();
  outb(0xA0,0x11);
  io_wait();
  outb(0x21,0x20);
  io_wait();
  outb(0xA1,0x28);
  io_wait();
  outb(0x21,0x4);
  io_wait();
  outb(0xA1,0x2);
  io_wait();
  outb(0x21,0x1);
  io_wait();
  outb(0xA1,0x1);
  io_wait();
  outb(0xA1,0xFF);
  io_wait();
  outb(0x21,0xFB);
  IRQmask = 0xFFFB; /* all IRQs are masked except IRQ2 */
}

void unmaskIRQ(int irq)
{
  IRQmask &= ~(1 << irq);
  if(irq < 8)
    outb(0x21, IRQmask & 0xFF);
  else
    outb(0xA1, IRQmask >> 8);
}

void maskIRQ(int irq)
{
  IRQmask |= (1 << irq);
  if(irq < 8)
    outb(0x21,IRQmask & 0xFF);
  else
    outb(0xA1,IRQmask >> 8);
}

void refreshIRQs(void)
{
  outb(0x21,IRQmask & 0xFF);
  outb(0xA1,IRQmask >> 8);
}