firmware/sdmmc.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2004 by Jens Arnold
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21 #include "config.h"
  22 #include "sdmmc.h"
  23
  24 /* helper function to extract n (<=32) bits from an arbitrary position.
  25    counting from MSB to LSB */
  26 unsigned long card_extract_bits(
  27     const unsigned long *p, /* the start of the bitfield array */
  28     unsigned int start,     /* bit no. to start reading  */
  29     unsigned int size)      /* how many bits to read */
  30 {
  31     unsigned int long_index, bit_index;
  32     unsigned long result;
  33
  34     /* we assume words of CSD/CID are stored most significant word first */
  35     start = 127 - start;
  36
  37     long_index = start / 32;
  38     bit_index = start % 32;
  39
  40     result = p[long_index] << bit_index;
  41
  42     if (bit_index + size > 32)    /* crossing longword boundary */
  43         result |= p[long_index+1] >> (32 - bit_index);
  44
  45     result >>= 32 - size;
  46
  47     return result;
  48 }