41e98f2789
[ Upstream commit 19408200c094858d952a90bf4977733dc89a4df5 ]
Add GENMASK_TYPE() which generalizes __GENMASK() to support different
types, and implement fixed-types versions of GENMASK() based on it.
The fixed-type version allows more strict checks to the min/max values
accepted, which is useful for defining registers like implemented by
i915 and xe drivers with their REG_GENMASK*() macros.
The strict checks rely on shift-count-overflow compiler check to fail
the build if a number outside of the range allowed is passed.
Example:
#define FOO_MASK GENMASK_U32(33, 4)
will generate a warning like:
include/linux/bits.h:51:27: error: right shift count >= width of type [-Werror=shift-count-overflow]
51 | type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h)))))
| ^~
The result is casted to the corresponding fixed width type. For
example, GENMASK_U8() returns an u8. Note that because of the C
promotion rules, GENMASK_U8() and GENMASK_U16() will immediately be
promoted to int if used in an expression. Regardless, the main goal is
not to get the correct type, but rather to enforce more checks at
compile time.
While GENMASK_TYPE() is crafted to cover all variants, including the
already existing GENMASK(), GENMASK_ULL() and GENMASK_U128(), for the
moment, only use it for the newly introduced GENMASK_U*(). The
consolidation will be done in a separate change.
Co-developed-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Stable-dep-of: 2ba5772e530f ("gpio: idio-16: Define fixed direction of the GPIO lines")
Signed-off-by: William Breathitt Gray <wbg@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
89 lines
2.8 KiB
C
89 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_BITS_H
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#define __LINUX_BITS_H
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#include <linux/const.h>
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#include <vdso/bits.h>
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#include <uapi/linux/bits.h>
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#include <asm/bitsperlong.h>
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#define BIT_MASK(nr) (UL(1) << ((nr) % BITS_PER_LONG))
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#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
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#define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG))
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#define BIT_ULL_WORD(nr) ((nr) / BITS_PER_LONG_LONG)
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#define BITS_PER_BYTE 8
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#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE)
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/*
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* Create a contiguous bitmask starting at bit position @l and ending at
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* position @h. For example
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* GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
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*/
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#if !defined(__ASSEMBLY__)
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/*
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* Missing asm support
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*
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* GENMASK_U*() depend on BITS_PER_TYPE() which relies on sizeof(),
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* something not available in asm. Nevertheless, fixed width integers is a C
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* concept. Assembly code can rely on the long and long long versions instead.
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*/
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#include <linux/build_bug.h>
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#include <linux/overflow.h>
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#define GENMASK_INPUT_CHECK(h, l) \
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(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
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__is_constexpr((l) > (h)), (l) > (h), 0)))
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/*
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* Generate a mask for the specified type @t. Additional checks are made to
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* guarantee the value returned fits in that type, relying on
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* -Wshift-count-overflow compiler check to detect incompatible arguments.
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* For example, all these create build errors or warnings:
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*
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* - GENMASK(15, 20): wrong argument order
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* - GENMASK(72, 15): doesn't fit unsigned long
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* - GENMASK_U32(33, 15): doesn't fit in a u32
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*/
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#define GENMASK_TYPE(t, h, l) \
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((t)(GENMASK_INPUT_CHECK(h, l) + \
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(type_max(t) << (l) & \
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type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h)))))
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#define GENMASK_U8(h, l) GENMASK_TYPE(u8, h, l)
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#define GENMASK_U16(h, l) GENMASK_TYPE(u16, h, l)
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#define GENMASK_U32(h, l) GENMASK_TYPE(u32, h, l)
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#define GENMASK_U64(h, l) GENMASK_TYPE(u64, h, l)
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#else /* defined(__ASSEMBLY__) */
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/*
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* BUILD_BUG_ON_ZERO is not available in h files included from asm files,
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* disable the input check if that is the case.
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*/
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#define GENMASK_INPUT_CHECK(h, l) 0
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#endif /* !defined(__ASSEMBLY__) */
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#define GENMASK(h, l) \
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(GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
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#define GENMASK_ULL(h, l) \
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(GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
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#if !defined(__ASSEMBLY__)
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/*
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* Missing asm support
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*
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* __GENMASK_U128() depends on _BIT128() which would not work
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* in the asm code, as it shifts an 'unsigned __init128' data
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* type instead of direct representation of 128 bit constants
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* such as long and unsigned long. The fundamental problem is
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* that a 128 bit constant will get silently truncated by the
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* gcc compiler.
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*/
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#define GENMASK_U128(h, l) \
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(GENMASK_INPUT_CHECK(h, l) + __GENMASK_U128(h, l))
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#endif
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#endif /* __LINUX_BITS_H */
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