LXR linux/arch/arm/mach-sa1100/include/mach/bitfield.h

   1/*
   2 *      FILE            bitfield.h
   3 *
   4 *      Version         1.1
   5 *      Author          Copyright (c) Marc A. Viredaz, 1998
   6 *                      DEC Western Research Laboratory, Palo Alto, CA
   7 *      Date            April 1998 (April 1997)
   8 *      System          Advanced RISC Machine (ARM)
   9 *      Language        C or ARM Assembly
  10 *      Purpose         Definition of macros to operate on bit fields.
  11 */
  12
  13
  14
  15#ifndef __BITFIELD_H
  16#define __BITFIELD_H
  17
  18#ifndef __ASSEMBLY__
  19#define UData(Data)     ((unsigned long) (Data))
  20#else
  21#define UData(Data)     (Data)
  22#endif
  23
  24
  25/*
  26 * MACRO: Fld
  27 *
  28 * Purpose
  29 *    The macro "Fld" encodes a bit field, given its size and its shift value
  30 *    with respect to bit 0.
  31 *
  32 * Note
  33 *    A more intuitive way to encode bit fields would have been to use their
  34 *    mask. However, extracting size and shift value information from a bit
  35 *    field's mask is cumbersome and might break the assembler (255-character
  36 *    line-size limit).
  37 *
  38 * Input
  39 *    Size              Size of the bit field, in number of bits.
  40 *    Shft              Shift value of the bit field with respect to bit 0.
  41 *
  42 * Output
  43 *    Fld               Encoded bit field.
  44 */
  45
  46#define Fld(Size, Shft) (((Size) << 16) + (Shft))
  47
  48
  49/*
  50 * MACROS: FSize, FShft, FMsk, FAlnMsk, F1stBit
  51 *
  52 * Purpose
  53 *    The macros "FSize", "FShft", "FMsk", "FAlnMsk", and "F1stBit" return
  54 *    the size, shift value, mask, aligned mask, and first bit of a
  55 *    bit field.
  56 *
  57 * Input
  58 *    Field             Encoded bit field (using the macro "Fld").
  59 *
  60 * Output
  61 *    FSize             Size of the bit field, in number of bits.
  62 *    FShft             Shift value of the bit field with respect to bit 0.
  63 *    FMsk              Mask for the bit field.
  64 *    FAlnMsk           Mask for the bit field, aligned on bit 0.
  65 *    F1stBit           First bit of the bit field.
  66 */
  67
  68#define FSize(Field)    ((Field) >> 16)
  69#define FShft(Field)    ((Field) & 0x0000FFFF)
  70#define FMsk(Field)     (((UData (1) << FSize (Field)) - 1) << FShft (Field))
  71#define FAlnMsk(Field)  ((UData (1) << FSize (Field)) - 1)
  72#define F1stBit(Field)  (UData (1) << FShft (Field))
  73
  74
  75/*
  76 * MACRO: FInsrt
  77 *
  78 * Purpose
  79 *    The macro "FInsrt" inserts a value into a bit field by shifting the
  80 *    former appropriately.
  81 *
  82 * Input
  83 *    Value             Bit-field value.
  84 *    Field             Encoded bit field (using the macro "Fld").
  85 *
  86 * Output
  87 *    FInsrt            Bit-field value positioned appropriately.
  88 */
  89
  90#define FInsrt(Value, Field) \
  91                        (UData (Value) << FShft (Field))
  92
  93
  94/*
  95 * MACRO: FExtr
  96 *
  97 * Purpose
  98 *    The macro "FExtr" extracts the value of a bit field by masking and
  99 *    shifting it appropriately.
 100 *
 101 * Input
 102 *    Data              Data containing the bit-field to be extracted.
 103 *    Field             Encoded bit field (using the macro "Fld").
 104 *
 105 * Output
 106 *    FExtr             Bit-field value.
 107 */
 108
 109#define FExtr(Data, Field) \
 110                        ((UData (Data) >> FShft (Field)) & FAlnMsk (Field))
 111
 112
 113#endif /* __BITFIELD_H */
 114