Re: [PATCH v2 4/5] arch/riscv: Add bitrev.h file to support rev8 and brev8

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Selecting GENERIC_BITREVERSE conditionally on HAVE_ARCH_BITREVERSE causes a Kconfig unmet direct dependency warning when BITREVERSE is built as a module.
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commit 500623b90fe7e30bdea603dfb1e1f54158143ee4
Author: Jinjie Ruan <ruanjinjie@huawei.com>

arch/riscv: Add bitrev.h file to support rev8 and brev8

This commit utilizes the RISC-V Zbkb brev8 and rev8 instructions to
efficiently implement bit reversal. It conditionally selects
HAVE_ARCH_BITREVERSE and GENERIC_BITREVERSE when the extension is available.

Link: https://docs.riscv.org/reference/isa/unpriv/b-st-ext.html

> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index d235396c45141..a708583f785db 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -104,6 +104,7 @@ config RISCV
>  	select FUNCTION_ALIGNMENT_8B if DYNAMIC_FTRACE_WITH_CALL_OPS
>  	select GENERIC_ARCH_TOPOLOGY
>  	select GENERIC_ATOMIC64 if !64BIT
> +	select GENERIC_BITREVERSE if HAVE_ARCH_BITREVERSE

Will this cause an unmet direct dependency warning if BITREVERSE is built
as a module?

In lib/Kconfig, GENERIC_BITREVERSE is a tristate symbol that has a dependency
on BITREVERSE. Because HAVE_ARCH_BITREVERSE is a boolean symbol, if BITREVERSE
is configured as a module (=m), the condition for HAVE_ARCH_BITREVERSE below
evaluates to m but Kconfig automatically promotes it to y.

This forces GENERIC_BITREVERSE to y while its required dependency BITREVERSE
is only m.

Should this select also inherit the dependency (e.g., select
GENERIC_BITREVERSE if HAVE_ARCH_BITREVERSE && BITREVERSE) to cap the
selection strength and avoid the warning?

[ ... ]
> @@ -128,6 +129,7 @@ config RISCV
>  	select HAS_IOPORT if MMU
>  	select HAVE_ALIGNED_STRUCT_PAGE
>  	select HAVE_ARCH_AUDITSYSCALL
> +	select HAVE_ARCH_BITREVERSE if RISCV_ISA_ZBKB && BITREVERSE

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260506175207.110893-1-ynorov@nvidia.com?part=4