linux-kernel - Re: [PATCH v3 1/6] RISC-V: Correctly print supported extensions

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Date:   Tue, 15 Feb 2022 15:11:06 +0530
From:   Anup Patel <anup@...infault.org>
To:     Atish Patra <atishp@...osinc.com>
Cc:     "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Tsukasa OI <research_trasio@....a4lg.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atishp@...shpatra.org>,
        Damien Le Moal <damien.lemoal@....com>,
        DTML <devicetree@...r.kernel.org>,
        Jisheng Zhang <jszhang@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v3 1/6] RISC-V: Correctly print supported extensions

On Tue, Feb 15, 2022 at 2:32 PM Atish Patra <atishp@...osinc.com> wrote:
>
> From: Tsukasa OI <research_trasio@....a4lg.com>
>
> This commit replaces BITS_PER_LONG with number of alphabet letters.
>
> Current ISA pretty-printing code expects extension 'a' (bit 0) through
> 'z' (bit 25).  Although bit 26 and higher is not currently used (thus never
> cause an issue in practice), it will be an annoying problem if we start to
> use those in the future.
>
> This commit disables printing high bits for now.
>
> Signed-off-by: Tsukasa OI <research_trasio@....a4lg.com>
> Signed-off-by: Atish Patra <atishp@...osinc.com>
> Tested-by: Heiko Stuebner <heiko@...ech.de>

Looks good to me.

Reviewed-by: Anup Patel <anup@...infault.org>

Regards,
Anup

> ---
>  arch/riscv/kernel/cpufeature.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index d959d207a40d..dd3d57eb4eea 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -13,6 +13,8 @@
>  #include <asm/smp.h>
>  #include <asm/switch_to.h>
>
> +#define NUM_ALPHA_EXTS ('z' - 'a' + 1)
> +
>  unsigned long elf_hwcap __read_mostly;
>
>  /* Host ISA bitmap */
> @@ -63,7 +65,7 @@ void __init riscv_fill_hwcap(void)
>  {
>         struct device_node *node;
>         const char *isa;
> -       char print_str[BITS_PER_LONG + 1];
> +       char print_str[NUM_ALPHA_EXTS + 1];
>         size_t i, j, isa_len;
>         static unsigned long isa2hwcap[256] = {0};
>
> @@ -133,13 +135,13 @@ void __init riscv_fill_hwcap(void)
>         }
>
>         memset(print_str, 0, sizeof(print_str));
> -       for (i = 0, j = 0; i < BITS_PER_LONG; i++)
> +       for (i = 0, j = 0; i < NUM_ALPHA_EXTS; i++)
>                 if (riscv_isa[0] & BIT_MASK(i))
>                         print_str[j++] = (char)('a' + i);
>         pr_info("riscv: ISA extensions %s\n", print_str);
>
>         memset(print_str, 0, sizeof(print_str));
> -       for (i = 0, j = 0; i < BITS_PER_LONG; i++)
> +       for (i = 0, j = 0; i < NUM_ALPHA_EXTS; i++)
>                 if (elf_hwcap & BIT_MASK(i))
>                         print_str[j++] = (char)('a' + i);
>         pr_info("riscv: ELF capabilities %s\n", print_str);
> --
> 2.30.2
>