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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>,
	"Björn Töpel" <bjorn@kernel.org>,
	linux-arch@vger.kernel.org
Subject: Re: [PATCH v2 2/2] riscv: introduce asm/swab.h
Date: Thu, 20 Mar 2025 20:37:18 -0700	[thread overview]
Message-ID: <20250321033718.GA98513@sol.localdomain> (raw)
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

WARNING: multiple messages have this Message-ID (diff)
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>,
	"Björn Töpel" <bjorn@kernel.org>,
	linux-arch@vger.kernel.org
Subject: Re: [PATCH v2 2/2] riscv: introduce asm/swab.h
Date: Thu, 20 Mar 2025 20:37:18 -0700	[thread overview]
Message-ID: <20250321033718.GA98513@sol.localdomain> (raw)
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

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2025-03-21  3:37 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-03-19 21:09 [PATCH v2 0/2] Implement endianness swap macros for RISC-V Ignacio Encinas
2025-03-19 21:09 ` Ignacio Encinas
2025-03-19 21:09 ` [PATCH v2 1/2] include/uapi/linux/swab.h: move default implementation for swab macros into asm-generic Ignacio Encinas
2025-03-19 21:09   ` Ignacio Encinas
2025-03-19 21:12   ` Arnd Bergmann
2025-03-19 21:12     ` Arnd Bergmann
2025-03-19 21:37     ` Ignacio Encinas Rubio
2025-03-19 21:37       ` Ignacio Encinas Rubio
2025-03-19 21:49       ` Arnd Bergmann
2025-03-19 21:49         ` Arnd Bergmann
2025-03-20 22:36         ` Ignacio Encinas Rubio
2025-03-20 22:36           ` Ignacio Encinas Rubio
2025-03-21 10:23           ` Arnd Bergmann
2025-03-21 10:23             ` Arnd Bergmann
2025-03-21 18:38             ` Ignacio Encinas Rubio
2025-03-21 18:38               ` Ignacio Encinas Rubio
2025-03-19 21:09 ` [PATCH v2 2/2] riscv: introduce asm/swab.h Ignacio Encinas
2025-03-19 21:09   ` Ignacio Encinas
2025-03-21  3:37   ` Eric Biggers [this message]
2025-03-21  3:37     ` Eric Biggers
2025-03-21 21:07     ` Ignacio Encinas Rubio
2025-03-21 21:07       ` Ignacio Encinas Rubio

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