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The generic bit reversal implementation is controlled by
!HAVE_ARCH_BITREVERSE. This makes it difficult for architectures to
provide a hardware-accelerated implementation while being able to
fall back to the generic version if needed.
This patch adds GENERIC_BITREVERSE, so bitreverse API is controlled by
BITREVERSE, GENERIC_BITREVERSE and HAVE_ARCH_BITREVERSE options. The
relationship between them is described as follows:
- BITREVERSE is selected by user code; it's required to generate the API;
- Architectures may select HAVE_ARCH_BITREVERSE and provide an arch
implementation in arch/$(ARCH)/include/asm/bitrev.h.
- if HAVE_ARCH_BITREVERSE isn't set, BITREVERSE selects GENERIC_BITREVERSE;
- if GENERIC_BITREVERSE is set and HAVE_ARCH_BITREVERSE is not, the kernel
provides generic implementation only, and wires bitrevXX() to it.
- if HAVE_ARCH_BITREVERSE is set and GENERIC_BITREVERSE is not, the arch
code provides __arch_bitrevXX(), and it is wired to bitrevXX();
- if both GENERIC_BITREVERSE and HAVE_ARCH_BITREVERSE are selected, the kernel
generates generic___bitrev(), but wires bitrev() to the __arch_bitrev().
The last option allows architectures to use generic___bitrev() as a
fallback option.
Drivers and core code should never select GENERIC_BITREVERSE or
HAVE_ARCH_BITREVERSE explicitly.
Architectures that require generic bitreverse API as a fallback should
explicitly enable GENERIC_BITREVERSE together with HAVE_ARCH_BITREVERSE.
Signed-off-by: Yury Norov <ynorov@nvidia.com>
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Add SPDX license identifiers to all files which:
- Have no license information of any form
- Have MODULE_LICENCE("GPL*") inside which was used in the initial
scan/conversion to ignore the file
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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this change add CONFIG_HAVE_ARCH_BITREVERSE config option,
so that we can use some architecture's bitrev hardware instruction
to do bitrev operation.
Introduce __constant_bitrev* macro for constant bitrev operation.
Change __bitrev16() __bitrev32() to be inline function,
don't need export symbol for these tiny functions.
Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Bluetooth will be able to use this.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Dave Young <hidave.darkstar@gmail.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add MODULE_* attributes to the new bit reversal library. Most notably
MODULE_LICENSE which prevents superfluous kernel tainting.
Signed-off-by: Cal Peake <cp@absolutedigital.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch provides two bit reverse functions and bit reverse table.
- reverse the order of bits in a u32 value
u8 bitrev8(u8 x);
- reverse the order of bits in a u32 value
u32 bitrev32(u32 x);
- byte reverse table
const u8 byte_rev_table[256];
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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