linux-kernel - RE: [PATCH 3/4] RISC-V: Support case insensitive ISA string parsing.

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Message-ID: <MN2PR04MB6061790AFE4E0AAA838678028DC30@MN2PR04MB6061.namprd04.prod.outlook.com>
Date:   Sat, 27 Jul 2019 02:23:42 +0000
From:   Anup Patel <Anup.Patel@....com>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Atish Patra <Atish.Patra@....com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alan Kao <alankao@...estech.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Allison Randal <allison@...utok.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        Palmer Dabbelt <palmer@...ive.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: RE: [PATCH 3/4] RISC-V: Support case insensitive ISA string parsing.



> -----Original Message-----
> From: Paul Walmsley <paul.walmsley@...ive.com>
> Sent: Saturday, July 27, 2019 5:00 AM
> To: Atish Patra <Atish.Patra@....com>
> Cc: linux-kernel@...r.kernel.org; Alan Kao <alankao@...estech.com>;
> Albert Ou <aou@...s.berkeley.edu>; Allison Randal <allison@...utok.net>;
> Anup Patel <Anup.Patel@....com>; Daniel Lezcano
> <daniel.lezcano@...aro.org>; Greg Kroah-Hartman
> <gregkh@...uxfoundation.org>; Johan Hovold <johan@...nel.org>; linux-
> riscv@...ts.infradead.org; Palmer Dabbelt <palmer@...ive.com>; Thomas
> Gleixner <tglx@...utronix.de>
> Subject: Re: [PATCH 3/4] RISC-V: Support case insensitive ISA string parsing.
> 
> On Fri, 26 Jul 2019, Atish Patra wrote:
> 
> > On 7/26/19 1:47 PM, Paul Walmsley wrote:
> > > On Fri, 26 Jul 2019, Atish Patra wrote:
> > >
> > > > As per riscv specification, ISA naming strings are case
> > > > insensitive. However, currently only lower case strings are parsed
> > > > during cpu procfs.
> > > >
> > > > Support parsing of upper case letters as well.
> > > >
> > > > Signed-off-by: Atish Patra <atish.patra@....com>
> > >
> > > Is there a use case that's driving this, or
> >
> > Currently, we use all lower case isa string in kvmtool. But somebody
> > can have uppercase letters in future as spec allows it.
> >
> >
> > can we just say, "use
> > > lowercase letters" and leave it at that?
> > >
> >
> > In that case, it will not comply with RISC-V spec. Is that okay ?
> 
> I think that section of the specification is mostly concerned with someone
> trying to define "f" as a different extension than "F", or something like that.
> I'm not sure that it imposes any constraint that software must accept both
> upper and lower case ISA strings.
> 
> What gives me pause here is that this winds up impacting DT schema
> validation:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Docu
> mentation/devicetree/bindings/riscv/cpus.yaml#n41

If 'f' and 'F' mean same extension as-per RISC-V spec then software should also
interpret it that way hence this patch.

Regards,
Anup