bitfield.h
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/*
* Copyright 2013 Broadcom Corporation.
*
* SPDX-License-Identifier: GPL-2.0+
*/
/*
* Bitfield operations
*
* These are generic bitfield operations which allow manipulation of variable
* width bitfields within a word. One use of this would be to use data tables
* to determine how to reprogram fields within R/W hardware registers.
*
* Example:
*
* old_reg_val
* +--------+----+---+--+-----+----------+
* | | | | | old | |
* +--------+----+---+--+-----+----------+
*
* new_reg_val
* +--------+----+---+--+-----+----------+
* | | | | | new | |
* +--------+----+---+--+-----+----------+
*
* mask = bitfield_mask(10, 5);
* old = bitfield_extract(old_reg_val, 10, 5);
* new_reg_val = bitfield_replace(old_reg_val, 10, 5, new);
*
* The numbers 10 and 5 could for example come from data
* tables which describe all bitfields in all registers.
*/
#include <linux/types.h>
/* Produces a mask of set bits covering a range of a uint value */
static inline uint bitfield_mask(uint shift, uint width)
{
return ((1 << width) - 1) << shift;
}
/* Extract the value of a bitfield found within a given register value */
static inline uint bitfield_extract(uint reg_val, uint shift, uint width)
{
return (reg_val & bitfield_mask(shift, width)) >> shift;
}
/*
* Replace the value of a bitfield found within a given register value
* Returns the newly modified uint value with the replaced field.
*/
static inline uint bitfield_replace(uint reg_val, uint shift, uint width,
uint bitfield_val)
{
uint mask = bitfield_mask(shift, width);
return (reg_val & ~mask) | (bitfield_val << shift);
}