source: bootcd/isolinux/syslinux-6.03/gpxe/src/include/gpxe/bitbash.h

#ifndef _GPXE_BITBASH_H
#define _GPXE_BITBASH_H

/** @file
 *
 * Bit-bashing interfaces
 *
 */

FILE_LICENCE ( GPL2_OR_LATER );

struct bit_basher;

/** Bit-bashing operations */
struct bit_basher_operations {
        /**
         * Set/clear output bit
         *
         * @v basher            Bit-bashing interface
         * @v bit_id            Bit number
         * @v data              Value to write
         * 
         * @c data will be 0 if a logic 0 should be written (i.e. the
         * bit should be cleared), or -1UL if a logic 1 should be
         * written (i.e. the bit should be set).  This is done so that
         * the method may simply binary-AND @c data with the
         * appropriate bit mask.
         */
        void ( * write ) ( struct bit_basher *basher, unsigned int bit_id,
                           unsigned long data );
        /**
         * Read input bit
         *
         * @v basher            Bit-bashing interface
         * @v bit_id            Bit number
         * @ret zero            Input is a logic 0
         * @ret non-zero        Input is a logic 1
         */
        int ( * read ) ( struct bit_basher *basher, unsigned int bit_id );
};

/** A bit-bashing interface */
struct bit_basher {
        /** Bit-bashing operations */
        struct bit_basher_operations *op;
};

extern void write_bit ( struct bit_basher *basher, unsigned int bit_id,
                        unsigned long data );
extern int read_bit ( struct bit_basher *basher, unsigned int bit_id );

#endif /* _GPXE_BITBASH_H */