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Date: Thu, 20 Mar 2025 20:37:18 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Ignacio Encinas <ignacio@iencinas.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Alexandre Ghiti <alex@ghiti.fr>, Arnd Bergmann <arnd@arndb.de>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-kernel-mentees@lists.linux.dev, skhan@linuxfoundation.org,
	Zhihang Shao <zhihang.shao.iscas@gmail.com>,
	=?iso-8859-1?Q?Bj=F6rn_T=F6pel?= <bjorn@kernel.org>,
	linux-arch@vger.kernel.org
Subject: Re: [PATCH v2 2/2] riscv: introduce asm/swab.h
Message-ID: <20250321033718.GA98513@sol.localdomain>
References: <20250319-riscv-swab-v2-0-d53b6d6ab915@iencinas.com>
 <20250319-riscv-swab-v2-2-d53b6d6ab915@iencinas.com>
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In-Reply-To: <20250319-riscv-swab-v2-2-d53b6d6ab915@iencinas.com>

On Wed, Mar 19, 2025 at 10:09:46PM +0100, Ignacio Encinas wrote:
> +#define ARCH_SWAB(size) \
> +static __always_inline unsigned long __arch_swab##size(__u##size value) \
> +{									\
> +	unsigned long x = value;					\
> +									\
> +	asm goto(ALTERNATIVE("j %l[legacy]", "nop", 0,			\
> +			     RISCV_ISA_EXT_ZBB, 1)			\
> +			     :::: legacy);				\

Is there a reason to use this instead of
riscv_has_extension_likely(RISCV_ISA_EXT_ZBB) which seems to do the same thing,
including using a static branch?

- Eric