mirror of
https://github.com/openwrt/openwrt.git
synced 2024-12-26 17:01:14 +00:00
ef94541c07
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 <ansuelsmth@gmail.com>
59 lines
2.2 KiB
Diff
59 lines
2.2 KiB
Diff
From e2192de59e457aef8d1f055a452131f0b3e5d097 Mon Sep 17 00:00:00 2001
|
|
From: Johannes Berg <johannes.berg@intel.com>
|
|
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 <johannes.berg@intel.com>
|
|
Link: https://lore.kernel.org/r/20230118142652.53f20593504b.Iaeea0aee77a6493d70e573b4aa55c91c00e01e4b@changeid
|
|
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
|
|
---
|
|
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
|