From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7481C4332F for ; Tue, 29 Nov 2022 16:59:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236535AbiK2Q7d (ORCPT ); Tue, 29 Nov 2022 11:59:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59530 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236525AbiK2Q7O (ORCPT ); Tue, 29 Nov 2022 11:59:14 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B877C711B5; Tue, 29 Nov 2022 08:54:27 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 6B4FFB816EC; Tue, 29 Nov 2022 16:54:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43C8CC433C1; Tue, 29 Nov 2022 16:54:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669740865; bh=erEU2/tP76EwU+ThPKM86bYsw7qd2xx2pYgzSbtO8XA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SHwHw/LWOp6C+IWACdDR/cOQWzR1oagbhGiejXa6B8cNvUGh466ZNvXg0wroHizFO ocj79LSfGPbZ6FEY5Cpbb5DRaLN0Yzo2buWZ6b2qquBK2wXXPti/4X904kaRVRd9Hw 2NGBelGZEbMt87XsXLpU0CBIA49FYPnCjaf27JdMPt12NKWHTFV3tVrQfBUqVN+hs3 7KPJn5LCkhJ+UmhRRjZjGkY/sKVal6xv9X97pvplS2FZLyReEL8+Pdhjm4yUfl0SEl 8TreKKdAV1zntdIfvp1DsEdUhp0NJhWxDlYrC1snxRKLHHiEVHU0mfSpSZcP80D7lg yjiDUuVnxU7fA== Date: Tue, 29 Nov 2022 16:54:19 +0000 From: Conor Dooley To: Andrew Jones Cc: Conor Dooley , linux-riscv@lists.infradead.org, aou@eecs.berkeley.edu, devicetree@vger.kernel.org, guoren@kernel.org, heiko@sntech.de, krzysztof.kozlowski+dt@linaro.org, linux-kernel@vger.kernel.org, palmer@dabbelt.com, paul.walmsley@sifive.com, robh+dt@kernel.org Subject: Re: [RFC 1/2] RISC-V: clarify ISA string ordering rules in cpu.c Message-ID: References: <20221129144742.2935581-2-conor.dooley@microchip.com> <20221129161223.gelsvctfnqg7pdwb@kamzik> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221129161223.gelsvctfnqg7pdwb@kamzik> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 29, 2022 at 05:12:23PM +0100, Andrew Jones wrote: > On Tue, Nov 29, 2022 at 02:47:42PM +0000, Conor Dooley wrote: > > While the list of rules may have been accurate when created, it now > > lacks some clarity in the face of isa-manual updates. Specifically: > > > > - there is no mention here of a distinction between regular 'Z' > > extensions which are "Additional Standard Extensions" and "Zxm" > > extensions which are "Standard Machine-Level Extensions" > > > > - there is also no explicit mention of where either should be sorted in > > the list > > > > - underscores are only required between two *multi-letter* extensions but > > the list of rules implies that this is required between a multi-letter > > extension and any other extension. IOW "rv64imafdzicsr_zifencei" is a > > valid string > > > > Attempt to clean up the list of rules, by adding information on the > > above & sprinkling in some white space for readability. > > > > Signed-off-by: Conor Dooley > > --- > > arch/riscv/kernel/cpu.c | 22 +++++++++++++++++----- > > 1 file changed, 17 insertions(+), 5 deletions(-) > > > > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c > > index 852ecccd8920..5e42c92a8456 100644 > > --- a/arch/riscv/kernel/cpu.c > > +++ b/arch/riscv/kernel/cpu.c > > @@ -120,20 +120,32 @@ device_initcall(riscv_cpuinfo_init); > > .uprop = #UPROP, \ > > .isa_ext_id = EXTID, \ > > } > > + > > /* > > * Here are the ordering rules of extension naming defined by RISC-V > > * specification : > > - * 1. All extensions should be separated from other multi-letter extensions > > - * by an underscore. > > + * > > + * 1. All multi-letter extensions should be separated from other multi-letter > > + * extensions by an underscore. > > + * > > * 2. The first letter following the 'Z' conventionally indicates the most > > * closely related alphabetical extension category, IMAFDQLCBKJTPVH. > > - * If multiple 'Z' extensions are named, they should be ordered first > > - * by category, then alphabetically within a category. > > + * 'Z' extensions should be sorted after single-letter extensions and before > > + * any higher-privileged extensions. > > + * If multiple 'Z' extensions are named, they should be ordered first by > > + * category, then alphabetically within a category. > > + * > > * 3. Standard supervisor-level extensions (starts with 'S') should be > > * listed after standard unprivileged extensions. If multiple > > * supervisor-level extensions are listed, they should be ordered > > * alphabetically. > > - * 4. Non-standard extensions (starts with 'X') must be listed after all > > + * > > + * 4 Standard machine-level extensions (starts with 'Zxm') should be > > + * listed after any lower-privileged, standard extensions. If multiple > > + * machine-level extensions are listed, they should be ordered > > + * alphabetically. > > + * > > + * 5. Non-standard extensions (starts with 'X') must be listed after all > > * standard extensions. They must be separated from other multi-letter > > * extensions by an underscore. > > */ > > -- > > 2.38.1 > > > > Alternatively, we could change the comment to just point out the spec > chapter and provide an example, e.g. IDK, maybe add the reference & the example but keep the summary? > /* > * The canonical order of ISA extension names in the ISA string is defined in > * chapter 27 of the unprivileged spec. An example string following the > * order is > * > * rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux > * > * Notice how Z-extensions are first sorted by category using the canonical > * order of the first letter following the Z. Extension groups are in the > * order specified in chapter 27. Extensions within each group are sorted > * alphabetically. > */ > > > Thanks, > drew