Re: [PATCH 7/7] RISC-V: add zbb support to string functions

From: Andrew Jones <ajones@ventanamicro.com>
To: Heiko Stuebner <heiko@sntech.de>
Cc: Conor Dooley <conor@kernel.org>,
	linux-riscv@lists.infradead.org, palmer@dabbelt.com,
	christoph.muellner@vrull.eu, prabhakar.csengg@gmail.com,
	philipp.tomsich@vrull.eu, emil.renner.berthing@canonical.com
Subject: Re: [PATCH 7/7] RISC-V: add zbb support to string functions
Date: Fri, 25 Nov 2022 08:49:33 +0100	[thread overview]
Message-ID: <20221125074933.2xuyaeuk5kmi5miw@kamzik> (raw)
In-Reply-To: <3259590.VLH7GnMWUR@phil>

On Fri, Nov 25, 2022 at 12:51:54AM +0100, Heiko Stuebner wrote:
> Am Donnerstag, 24. November 2022, 23:32:58 CET schrieb Conor Dooley:
> > On Thu, Nov 24, 2022 at 11:23:08PM +0100, Heiko Stübner wrote:
...
> > > > > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> > > > > index bf9dd6764bad..66ff36a57e20 100644
> > > > > --- a/arch/riscv/kernel/cpu.c
> > > > > +++ b/arch/riscv/kernel/cpu.c
> > > > > @@ -166,6 +166,7 @@ static struct riscv_isa_ext_data isa_ext_arr[] = {
> > > > >  	__RISCV_ISA_EXT_DATA(sstc, RISCV_ISA_EXT_SSTC),
> > > > >  	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
> > > > >  	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
> > > > > +	__RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZBB),
> > > > >  	__RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
> > > > >  	__RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
> > > > >  	__RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX),
> > > > 
> > > > This one I do know that Palmer wants canonically ordered.
> > 
> > btw, idk if you noticed but I appear to have picked canonical ordering
> > as today's thing to get confused about a lot.
> > 
> > You put zbb after the S extentions - does that meant it is *not* an
> > "Additional Standard Extension" but rather a regular Z one?
> 
> This confuses me completely now :-) .
>

Can we instead post a patch to the spec that changes the order to
alphabetical? The only other option I see is to develop a tool which sorts
extensions and every RISC-V developer keeps it in their back pocket. A
kernel specific tool to check each list we want to keep sorted would be
nice too.

My preference would be to change the spec to alphabetical order, though,
because the spec isn't explicit[*] enough to write a tool that can handle
all cases. We'll end up needing to have conversations like this one to
write the tool and eventually the tool will be what everyone looks to,
rather than the spec...

[*] The spec uses words like 'can', 'should', and 'conventional'.

Thanks,
drew

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