src/drivers/bitbash/bitbash.c

   1 /*
   2  * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 FILE_LICENCE ( GPL2_OR_LATER );
  20
  21 #include <gpxe/bitbash.h>
  22
  23 /** @file
  24  *
  25  * Bit-bashing interfaces
  26  *
  27  */
  28
  29 /**
  30  * Set/clear output bit
  31  *
  32  * @v basher            Bit-bashing interface
  33  * @v bit_id            Bit number
  34  * @v data              Value to write
  35  *
  36  * If @c data is 0, a logic 0 will be written.  If @c data is
  37  * non-zero, a logic 1 will be written.
  38  */
  39 void write_bit ( struct bit_basher *basher, unsigned int bit_id,
  40                  unsigned long data ) {
  41         basher->op->write ( basher, bit_id, ( data ? -1UL : 0 ) );
  42 }
  43
  44 /**
  45  * Read input bit
  46  *
  47  * @v basher            Bit-bashing interface
  48  * @v bit_id            Bit number
  49  * @ret data            Value read
  50  *
  51  * @c data will always be either 0 or -1UL.  The idea is that the
  52  * caller can simply binary-AND the returned value with whatever mask
  53  * it needs to apply.
  54  */
  55 int read_bit ( struct bit_basher *basher, unsigned int bit_id ) {
  56         return ( basher->op->read ( basher, bit_id ) ? -1UL : 0 );
  57 }