root/include/linux/mc6821.h

#ifndef _MC6821_H_
#define _MC6821_H_

/*
 * This file describes the memery mapping of the MC6821 PIA.
 * The unions describe overlayed registers. Which of them is used is
 * determined by bit 2 of the corresponding control register.
 * this files expects the PIA_REG_PADWIDTH to be defined the numeric
 * value of the register spacing.
 *
 * Data came from MFC-31-Developer Kit (from Ralph Seidel,
 * zodiac@darkness.gun.de) and Motorola Data Sheet (from 
 * Richard Hirst, srh@gpt.co.uk)
 *
 * 6.11.95 copyright Joerg Dorchain (dorchain@mpi-sb.mpg.de)
 *
 */

#ifndef PIA_REG_PADWIDTH
#define PIA_REG_PADWIDTH 255
#endif

struct pia {
        union {
                volatile u_char pra;
                volatile u_char ddra;
        } ua;
        u_char pad1[PIA_REG_PADWIDTH];
        volatile u_char cra;
        u_char pad2[PIA_REG_PADWIDTH];
        union {
                volatile u_char prb;
                volatile u_char ddrb;
        } ub;
        u_char pad3[PIA_REG_PADWIDTH];
        volatile u_char crb;
        u_char pad4[PIA_REG_PADWIDTH];
};

#define ppra ua.pra
#define pddra ua.ddra
#define pprb ub.prb
#define pddrb ub.ddrb

#define PIA_C1_ENABLE_IRQ (1<<0)
#define PIA_C1_LOW_TO_HIGH (1<<1)
#define PIA_DDR (1<<2)
#define PIA_IRQ2 (1<<6)
#define PIA_IRQ1 (1<<7)

#endif