From: Christian Marangi Date: Mon, 15 Jan 2024 21:47:20 +0000 (+0100) Subject: generic: 6.1: backport FIELD_PREP_CONST patch X-Git-Url: http://git.openwrt.org/?a=commitdiff_plain;h=ef94541c07b13d2c07bc92df8a52e2eeccd9b488;p=openwrt%2Fstaging%2Fjow.git generic: 6.1: backport FIELD_PREP_CONST patch Backport FIELD_PREP_CONST patch needed for at803x backport patches to correctly compile and work. This MACRO is needed to treat values derived from FIELD_PREP usage as const to be used by switch case or other needed usage. Signed-off-by: Christian Marangi --- diff --git a/target/linux/generic/backport-6.1/200-v6.3-bitfield-add-FIELD_PREP_CONST.patch b/target/linux/generic/backport-6.1/200-v6.3-bitfield-add-FIELD_PREP_CONST.patch new file mode 100644 index 0000000000..2e6d881fe9 --- /dev/null +++ b/target/linux/generic/backport-6.1/200-v6.3-bitfield-add-FIELD_PREP_CONST.patch @@ -0,0 +1,58 @@ +From e2192de59e457aef8d1f055a452131f0b3e5d097 Mon Sep 17 00:00:00 2001 +From: Johannes Berg +Date: Wed, 18 Jan 2023 14:26:53 +0100 +Subject: [PATCH] bitfield: add FIELD_PREP_CONST() + +Neither FIELD_PREP() nor *_encode_bits() can be used +in constant contexts (such as initializers), but we +don't want to define shift constants for all masks +just for use in initializers, and having checks that +the values fit is also useful. + +Therefore, add FIELD_PREP_CONST() which is a smaller +version of FIELD_PREP() that can only take constant +arguments and has less friendly (but not less strict) +error checks, and expands to a constant value. + +Signed-off-by: Johannes Berg +Link: https://lore.kernel.org/r/20230118142652.53f20593504b.Iaeea0aee77a6493d70e573b4aa55c91c00e01e4b@changeid +Signed-off-by: Johannes Berg +--- + include/linux/bitfield.h | 26 ++++++++++++++++++++++++++ + 1 file changed, 26 insertions(+) + +--- a/include/linux/bitfield.h ++++ b/include/linux/bitfield.h +@@ -115,6 +115,32 @@ + ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ + }) + ++#define __BF_CHECK_POW2(n) BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0) ++ ++/** ++ * FIELD_PREP_CONST() - prepare a constant bitfield element ++ * @_mask: shifted mask defining the field's length and position ++ * @_val: value to put in the field ++ * ++ * FIELD_PREP_CONST() masks and shifts up the value. The result should ++ * be combined with other fields of the bitfield using logical OR. ++ * ++ * Unlike FIELD_PREP() this is a constant expression and can therefore ++ * be used in initializers. Error checking is less comfortable for this ++ * version, and non-constant masks cannot be used. ++ */ ++#define FIELD_PREP_CONST(_mask, _val) \ ++ ( \ ++ /* mask must be non-zero */ \ ++ BUILD_BUG_ON_ZERO((_mask) == 0) + \ ++ /* check if value fits */ \ ++ BUILD_BUG_ON_ZERO(~((_mask) >> __bf_shf(_mask)) & (_val)) + \ ++ /* check if mask is contiguous */ \ ++ __BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask))) + \ ++ /* and create the value */ \ ++ (((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask)) \ ++ ) ++ + /** + * FIELD_GET() - extract a bitfield element + * @_mask: shifted mask defining the field's length and position