regfield.h

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/* KallistiOS ##version##
 
   kos/regfield.h
   Copyright (C) 2024 Paul Cercueil
 
   Macros to extract / insert bit fields
*/
 
/** \file    kos/regfield.h
    \brief   Macros to help dealing with register fields.
    \ingroup register_macros
 
    \author Paul Cercueil
*/
 
#ifndef __KOS_REGFIELD_H
#define __KOS_REGFIELD_H
 
#include <sys/cdefs.h>
__BEGIN_DECLS
 
/** \defgroup register_macros  Register Macros
    \brief                     Various macros used throughout the codebase
    \ingroup                   system
    
    @{
*/
 
/** \brief  Create a mask with a bit set
 
    \param  bit             The bit to set (from 0 to 31)
    \return                 A 32-bit mask with the corresponding bit set
 */
#define BIT(bit)        (1u << (bit))
 
/** \brief  Create a mask with a range of bits set
 
    \param  h               The high bit of the range to set, included
    \param  l               The low bit of the range to set, included
    \return                 A 32-bit mask with the corresponding bits set
 */
#define GENMASK(h, l)   ((0xffffffff << (l)) & (0xffffffff >> (31 - (h))))
 
/** \brief  Extract a field value from a variable
 
    \param  var             The 32-bit variable containing the field
    \param  field           A 32-bit mask that corresponds to the field
    \return                 The value of the field (shifted)
 */
#define FIELD_GET(var, field) \
        (((var) & (field)) >> __builtin_ctz(field))
 
/** \brief  Prepare a field with a given value
 
    \param  field           A 32-bit mask that corresponds to the field
    \param  value           The value to be put in the field
 */
#define FIELD_PREP(field, value) \
        (((value) << __builtin_ctz(field)) & (field))
 
/** @} */
 
__END_DECLS
#endif /* __KOS_REGFIELD_H */