diff options
Diffstat (limited to 'package')
| -rw-r--r-- | package/kernel/mac80211/patches/006-add-basic-register-field-manipulation-macros.patch | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/package/kernel/mac80211/patches/006-add-basic-register-field-manipulation-macros.patch b/package/kernel/mac80211/patches/006-add-basic-register-field-manipulation-macros.patch new file mode 100644 index 0000000000..a51edf8182 --- /dev/null +++ b/package/kernel/mac80211/patches/006-add-basic-register-field-manipulation-macros.patch @@ -0,0 +1,145 @@ +From: Jakub Kicinski <jakub.kicinski@netronome.com> +Date: Wed, 31 Aug 2016 12:46:44 +0100 +Subject: [PATCH] add basic register-field manipulation macros + +Common approach to accessing register fields is to define +structures or sets of macros containing mask and shift pair. +Operations on the register are then performed as follows: + + field = (reg >> shift) & mask; + + reg &= ~(mask << shift); + reg |= (field & mask) << shift; + +Defining shift and mask separately is tedious. Ivo van Doorn +came up with an idea of computing them at compilation time +based on a single shifted mask (later refined by Felix) which +can be used like this: + + #define REG_FIELD 0x000ff000 + + field = FIELD_GET(REG_FIELD, reg); + + reg &= ~REG_FIELD; + reg |= FIELD_PREP(REG_FIELD, field); + +FIELD_{GET,PREP} macros take care of finding out what the +appropriate shift is based on compilation time ffs operation. + +GENMASK can be used to define registers (which is usually +less error-prone and easier to match with datasheets). + +This approach is the most convenient I've seen so to limit code +multiplication let's move the macros to a global header file. +Attempts to use static inlines instead of macros failed due +to false positive triggering of BUILD_BUG_ON()s, especially with +GCC < 6.0. + +Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> +Reviewed-by: Dinan Gunawardena <dinan.gunawardena@netronome.com> +--- + create mode 100644 include/linux/bitfield.h + +--- /dev/null ++++ b/include/linux/bitfield.h +@@ -0,0 +1,100 @@ ++/* ++ * Copyright (C) 2014 Felix Fietkau <nbd@nbd.name> ++ * Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com> ++ * ++ * This program is free software; you can redistribute it and/or modify ++ * it under the terms of the GNU General Public License version 2 ++ * as published by the Free Software Foundation ++ * ++ * This program is distributed in the hope that it will be useful, ++ * but WITHOUT ANY WARRANTY; without even the implied warranty of ++ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ++ * GNU General Public License for more details. ++ */ ++ ++#ifndef _LINUX_BITFIELD_H ++#define _LINUX_BITFIELD_H ++ ++#include <linux/bug.h> ++ ++#ifdef __CHECKER__ ++#define __BUILD_BUG_ON_NOT_POWER_OF_2(n) (0) ++#else ++#define __BUILD_BUG_ON_NOT_POWER_OF_2(n) \ ++ BUILD_BUG_ON(((n) & ((n) - 1)) != 0) ++#endif ++ ++/* ++ * Bitfield access macros ++ * ++ * FIELD_{GET,PREP} macros take as first parameter shifted mask ++ * from which they extract the base mask and shift amount. ++ * Mask must be a compilation time constant. ++ * ++ * Example: ++ * ++ * #define REG_FIELD_A GENMASK(6, 0) ++ * #define REG_FIELD_B BIT(7) ++ * #define REG_FIELD_C GENMASK(15, 8) ++ * #define REG_FIELD_D GENMASK(31, 16) ++ * ++ * Get: ++ * a = FIELD_GET(REG_FIELD_A, reg); ++ * b = FIELD_GET(REG_FIELD_B, reg); ++ * ++ * Set: ++ * reg = FIELD_PREP(REG_FIELD_A, 1) | ++ * FIELD_PREP(REG_FIELD_B, 0) | ++ * FIELD_PREP(REG_FIELD_C, c) | ++ * FIELD_PREP(REG_FIELD_D, 0x40); ++ * ++ * Modify: ++ * reg &= ~REG_FIELD_C; ++ * reg |= FIELD_PREP(REG_FIELD_C, c); ++ */ ++ ++#define __bf_shf(x) (__builtin_ffsll(x) - 1) ++ ++#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \ ++ ({ \ ++ BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \ ++ _pfx "mask is not constant"); \ ++ BUILD_BUG_ON_MSG(!(_mask), _pfx "mask is zero"); \ ++ BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ ++ ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ ++ _pfx "value too large for the field"); \ ++ BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \ ++ _pfx "type of reg too small for mask"); \ ++ __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \ ++ (1ULL << __bf_shf(_mask))); \ ++ }) ++ ++/** ++ * FIELD_PREP() - prepare a bitfield element ++ * @_mask: shifted mask defining the field's length and position ++ * @_val: value to put in the field ++ * ++ * FIELD_PREP() masks and shifts up the value. The result should ++ * be combined with other fields of the bitfield using logical OR. ++ */ ++#define FIELD_PREP(_mask, _val) \ ++ ({ \ ++ __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ ++ ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ ++ }) ++ ++/** ++ * FIELD_GET() - extract a bitfield element ++ * @_mask: shifted mask defining the field's length and position ++ * @_reg: 32bit value of entire bitfield ++ * ++ * FIELD_GET() extracts the field specified by @_mask from the ++ * bitfield passed in as @_reg by masking and shifting it down. ++ */ ++#define FIELD_GET(_mask, _reg) \ ++ ({ \ ++ __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ ++ (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ ++ }) ++ ++#endif |