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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Mon, 18 Feb 2019 12:06:26 +0900
Message-ID: <CAK7LNARo5Sd-2rpHtFMfxEuEUej4P8oSbUdV+-EBp+V8qU+Gww@mail.gmail.com>
Subject: Re: [PATCH 10/11] lib: consolidate the GENERIC_HWEIGHT symbol
To:     Christoph Hellwig <hch@lst.de>
Cc:     linux-xtensa@linux-xtensa.org,
        linux-s390 <linux-s390@vger.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-riscv@lists.infradead.org,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
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On Thu, Feb 14, 2019 at 2:41 AM Christoph Hellwig <hch@lst.de> wrote:
>
> Introduce a new ARCH_HAS_HWEIGHT symbol for alpha and ia64,


I think this is really confusing.


"ARCH has its own optimized hweight implementation"

   is not equivalent to

"ARCH does not need generic hweight at all".


For example, see

arch/powerpc/lib/hweight_64.S


As far as I understood the code,
it will fallback to generic lib/hweight.c
if it turns out the optimized one is not available.


Thanks.


> and just
> default to the generic version otherwise.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  arch/alpha/Kconfig      | 5 +----
>  arch/arc/Kconfig        | 3 ---
>  arch/arm/Kconfig        | 4 ----
>  arch/arm64/Kconfig      | 3 ---
>  arch/c6x/Kconfig        | 3 ---
>  arch/csky/Kconfig       | 3 ---
>  arch/h8300/Kconfig      | 3 ---
>  arch/hexagon/Kconfig    | 3 ---
>  arch/ia64/Kconfig       | 1 +
>  arch/m68k/Kconfig       | 4 ----
>  arch/microblaze/Kconfig | 3 ---
>  arch/mips/Kconfig       | 4 ----
>  arch/nds32/Kconfig      | 3 ---
>  arch/nios2/Kconfig      | 3 ---
>  arch/openrisc/Kconfig   | 3 ---
>  arch/parisc/Kconfig     | 4 ----
>  arch/powerpc/Kconfig    | 4 ----
>  arch/riscv/Kconfig      | 3 ---
>  arch/s390/Kconfig       | 3 ---
>  arch/sh/Kconfig         | 3 ---
>  arch/sparc/Kconfig      | 4 ----
>  arch/unicore32/Kconfig  | 3 ---
>  arch/x86/Kconfig        | 3 ---
>  arch/x86/um/Kconfig     | 3 ---
>  arch/xtensa/Kconfig     | 3 ---
>  lib/Kconfig             | 7 +++++++
>  26 files changed, 9 insertions(+), 79 deletions(-)
>
> diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
> index 65b5514e5a7f..a549c53563e8 100644
> --- a/arch/alpha/Kconfig
> +++ b/arch/alpha/Kconfig
> @@ -2,6 +2,7 @@
>  config ALPHA
>         bool
>         default y
> +       select ARCH_HAS_HWEIGHT if ALPHA_EV67
>         select ARCH_MIGHT_HAVE_PC_PARPORT
>         select ARCH_MIGHT_HAVE_PC_SERIO
>         select ARCH_NO_PREEMPT
> @@ -446,10 +447,6 @@ config ALPHA_IRONGATE
>         depends on ALPHA_NAUTILUS
>         default y
>
> -config GENERIC_HWEIGHT
> -       bool
> -       default y if !ALPHA_EV67
> -
>  config ALPHA_AVANTI
>         bool
>         depends on ALPHA_XL || ALPHA_AVANTI_CH
> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> index 6476404b98b8..8bf4c0f7cc1d 100644
> --- a/arch/arc/Kconfig
> +++ b/arch/arc/Kconfig
> @@ -72,9 +72,6 @@ config MMU
>  config NO_IOPORT_MAP
>         def_bool y
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config HAVE_ARCH_TRANSPARENT_HUGEPAGE
>         def_bool y
>         depends on ARC_MMU_V4
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index c230fb1e09ba..b47825767e3d 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -182,10 +182,6 @@ config ARCH_HAS_BANDGAP
>  config FIX_EARLYCON_MEM
>         def_bool y if MMU
>
> -config GENERIC_HWEIGHT
> -       bool
> -       default y
> -
>  config ARCH_MAY_HAVE_PC_FDC
>         bool
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 7cc3334aba29..98c3776ccf6b 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -237,9 +237,6 @@ config ILLEGAL_POINTER_VALUE
>         hex
>         default 0xdead000000000000
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config ZONE_DMA32
>         def_bool y
>
> diff --git a/arch/c6x/Kconfig b/arch/c6x/Kconfig
> index 19b145ef7d92..c439d2f46af0 100644
> --- a/arch/c6x/Kconfig
> +++ b/arch/c6x/Kconfig
> @@ -28,9 +28,6 @@ config MMU
>  config FPU
>         def_bool n
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config C6X_BIG_KERNEL
>         bool "Build a big kernel"
>         help
> diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
> index c0a49cbd3df0..14a9905e99a4 100644
> --- a/arch/csky/Kconfig
> +++ b/arch/csky/Kconfig
> @@ -84,9 +84,6 @@ config CPU_NO_USER_BKPT
>           instruction exception.
>           In kernel we parse the *regs->pc to determine whether to send SIGTRAP or not.
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config MMU
>         def_bool y
>
> diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig
> index 4f5a1efab822..77ce104bb42e 100644
> --- a/arch/h8300/Kconfig
> +++ b/arch/h8300/Kconfig
> @@ -27,9 +27,6 @@ config H8300
>  config CPU_BIG_ENDIAN
>         def_bool y
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config NO_IOPORT_MAP
>         def_bool y
>
> diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
> index 7a01f4c5a4f6..fb2996063d5a 100644
> --- a/arch/hexagon/Kconfig
> +++ b/arch/hexagon/Kconfig
> @@ -61,9 +61,6 @@ config MMU
>  config GENERIC_IRQ_PROBE
>         def_bool y
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  menu "Machine selection"
>
>  choice
> diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
> index fc44c046953e..c9eb106b1f4c 100644
> --- a/arch/ia64/Kconfig
> +++ b/arch/ia64/Kconfig
> @@ -8,6 +8,7 @@ menu "Processor type and features"
>
>  config IA64
>         bool
> +       select ARCH_HAS_HWEIGHT
>         select ARCH_MIGHT_HAVE_PC_PARPORT
>         select ARCH_MIGHT_HAVE_PC_SERIO
>         select ACPI if (!IA64_HP_SIM)
> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> index 1bf6abaea604..91b150b6572c 100644
> --- a/arch/m68k/Kconfig
> +++ b/arch/m68k/Kconfig
> @@ -38,10 +38,6 @@ config ARCH_HAS_ILOG2_U32
>  config ARCH_HAS_ILOG2_U64
>         bool
>
> -config GENERIC_HWEIGHT
> -       bool
> -       default y
> -
>  config TIME_LOW_RES
>         bool
>         default y
> diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
> index d8907d6f969c..0185ac1f0268 100644
> --- a/arch/microblaze/Kconfig
> +++ b/arch/microblaze/Kconfig
> @@ -71,9 +71,6 @@ config ARCH_HAS_ILOG2_U32
>  config ARCH_HAS_ILOG2_U64
>         def_bool n
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  source "arch/microblaze/Kconfig.platform"
>
>  menu "Processor type and features"
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index bd0c9be7e7cf..04e041cac595 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -1042,10 +1042,6 @@ source "arch/mips/paravirt/Kconfig"
>
>  endmenu
>
> -config GENERIC_HWEIGHT
> -       bool
> -       default y
> -
>  config SCHED_OMIT_FRAME_POINTER
>         bool
>         default y
> diff --git a/arch/nds32/Kconfig b/arch/nds32/Kconfig
> index 7b3a36705aa8..979661f0ab51 100644
> --- a/arch/nds32/Kconfig
> +++ b/arch/nds32/Kconfig
> @@ -50,9 +50,6 @@ config NDS32
>         help
>           Andes(nds32) Linux support.
>
> -config GENERIC_HWEIGHT
> -        def_bool y
> -
>  config GENERIC_LOCKBREAK
>          def_bool y
>         depends on PREEMPT
> diff --git a/arch/nios2/Kconfig b/arch/nios2/Kconfig
> index 11ef63217ebe..a0485f5f0db0 100644
> --- a/arch/nios2/Kconfig
> +++ b/arch/nios2/Kconfig
> @@ -27,9 +27,6 @@ config NIOS2
>         select CPU_NO_EFFICIENT_FFS
>         select ARCH_DISCARD_MEMBLOCK
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config NO_IOPORT_MAP
>         def_bool y
>
> diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
> index 15d7df402c19..dc026973e6f6 100644
> --- a/arch/openrisc/Kconfig
> +++ b/arch/openrisc/Kconfig
> @@ -46,9 +46,6 @@ config CPU_BIG_ENDIAN
>  config MMU
>         def_bool y
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config NO_IOPORT_MAP
>         def_bool y
>
> diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
> index 42282b8e086d..7d5ded83c180 100644
> --- a/arch/parisc/Kconfig
> +++ b/arch/parisc/Kconfig
> @@ -86,10 +86,6 @@ config ARCH_HAS_ILOG2_U64
>         bool
>         default n
>
> -config GENERIC_HWEIGHT
> -       bool
> -       default y
> -
>  config TIME_LOW_RES
>         bool
>         depends on SMP
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index a0e9207893c8..8dd4d2b24fdb 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -96,10 +96,6 @@ config GENERIC_LOCKBREAK
>         default y
>         depends on SMP && PREEMPT
>
> -config GENERIC_HWEIGHT
> -       bool
> -       default y
> -
>  config ARCH_HAS_DMA_SET_COHERENT_MASK
>          bool
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 2b173a48bdbc..0acdd7aaaaea 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -69,9 +69,6 @@ config PAGE_OFFSET
>         default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
>         default 0xffffffe000000000 if 64BIT && MAXPHYSMEM_128GB
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config PGTABLE_LEVELS
>         int
>         default 3 if 64BIT
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 2a5c12be633e..9a25e19364f5 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -14,9 +14,6 @@ config ARCH_HAS_ILOG2_U32
>  config ARCH_HAS_ILOG2_U64
>         def_bool n
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config GENERIC_LOCKBREAK
>         def_bool y if SMP && PREEMPT
>
> diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
> index 3d0bd7fbe11a..af6a40af1702 100644
> --- a/arch/sh/Kconfig
> +++ b/arch/sh/Kconfig
> @@ -94,9 +94,6 @@ config ARCH_DEFCONFIG
>         default "arch/sh/configs/shx3_defconfig" if SUPERH32
>         default "arch/sh/configs/cayman_defconfig" if SUPERH64
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config GENERIC_LOCKBREAK
>         def_bool y
>         depends on SMP && PREEMPT
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 58270c021b01..78135ac357ed 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -187,10 +187,6 @@ config NR_CPUS
>
>  source "kernel/Kconfig.hz"
>
> -config GENERIC_HWEIGHT
> -       bool
> -       default y
> -
>  config ARCH_MAY_HAVE_PC_FDC
>         bool
>         default y
> diff --git a/arch/unicore32/Kconfig b/arch/unicore32/Kconfig
> index 9de1d983a99a..e69a8c3232e1 100644
> --- a/arch/unicore32/Kconfig
> +++ b/arch/unicore32/Kconfig
> @@ -38,9 +38,6 @@ config ARCH_HAS_ILOG2_U32
>  config ARCH_HAS_ILOG2_U64
>         bool
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config ARCH_MAY_HAVE_PC_FDC
>         bool
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index f4cb31174e1b..7a9347c7448e 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -255,9 +255,6 @@ config GENERIC_ISA_DMA
>         def_bool y
>         depends on ISA_DMA_API
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config ARCH_MAY_HAVE_PC_FDC
>         def_bool y
>         depends on ISA_DMA_API
> diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
> index f5a8cded3ca4..1628a54af003 100644
> --- a/arch/x86/um/Kconfig
> +++ b/arch/x86/um/Kconfig
> @@ -49,6 +49,3 @@ config ARCH_HAS_SC_SIGNALS
>
>  config ARCH_REUSE_HOST_VSYSCALL_AREA
>         def_bool !64BIT
> -
> -config GENERIC_HWEIGHT
> -       def_bool y
> diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
> index d02c25184ca0..ff57afdeda04 100644
> --- a/arch/xtensa/Kconfig
> +++ b/arch/xtensa/Kconfig
> @@ -47,9 +47,6 @@ config XTENSA
>           with reasonable minimum requirements.  The Xtensa Linux project has
>           a home page at <http://www.linux-xtensa.org/>.
>
> -config GENERIC_HWEIGHT
> -       def_bool y
> -
>  config ARCH_HAS_ILOG2_U32
>         def_bool n
>
> diff --git a/lib/Kconfig b/lib/Kconfig
> index bd2e7e74c321..91019f26d0a8 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -35,6 +35,13 @@ config RATIONAL
>  config GENERIC_CSUM
>         bool
>
> +config ARCH_HAS_HWEIGHT
> +       bool
> +
> +config GENERIC_HWEIGHT
> +       default y if !ARCH_HAS_HWEIGHT
> +       bool
> +
>  config GENERIC_STRNCPY_FROM_USER
>         bool
>
> --
> 2.20.1
>
>
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> linux-riscv@lists.infradead.org
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--
Best Regards
Masahiro Yamada