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c69abd801b
The new bitfield value must not be higher than its mask. Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@freescale.com> Reviewed-by: Joe Hershberger <joe.hershberger@ni.com>
58 lines
1.7 KiB
C
58 lines
1.7 KiB
C
/*
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* Copyright 2013 Broadcom Corporation.
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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/*
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* Bitfield operations
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*
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* These are generic bitfield operations which allow manipulation of variable
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* width bitfields within a word. One use of this would be to use data tables
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* to determine how to reprogram fields within R/W hardware registers.
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*
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* Example:
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*
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* old_reg_val
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* +--------+----+---+--+-----+----------+
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* | | | | | old | |
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* +--------+----+---+--+-----+----------+
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*
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* new_reg_val
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* +--------+----+---+--+-----+----------+
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* | | | | | new | |
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* +--------+----+---+--+-----+----------+
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*
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* mask = bitfield_mask(10, 5);
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* old = bitfield_extract(old_reg_val, 10, 5);
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* new_reg_val = bitfield_replace(old_reg_val, 10, 5, new);
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*
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* The numbers 10 and 5 could for example come from data
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* tables which describe all bitfields in all registers.
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*/
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#include <linux/types.h>
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/* Produces a mask of set bits covering a range of a uint value */
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static inline uint bitfield_mask(uint shift, uint width)
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{
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return ((1 << width) - 1) << shift;
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}
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/* Extract the value of a bitfield found within a given register value */
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static inline uint bitfield_extract(uint reg_val, uint shift, uint width)
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{
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return (reg_val & bitfield_mask(shift, width)) >> shift;
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}
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/*
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* Replace the value of a bitfield found within a given register value
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* Returns the newly modified uint value with the replaced field.
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*/
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static inline uint bitfield_replace(uint reg_val, uint shift, uint width,
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uint bitfield_val)
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{
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uint mask = bitfield_mask(shift, width);
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return (reg_val & ~mask) | ((bitfield_val << shift) & mask);
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}
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