root/arch/arm/mach-sa1100/include/mach/bitfield.h

INCLUDED FROM

   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 */