linux-kernel - Re: [PATCH v2 10/10] RISC-V: provide a Kconfig option to disable parsing "riscv,isa"

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Date:   Fri, 30 Jun 2023 09:46:48 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Conor Dooley <conor@...nel.org>
Cc:     Palmer Dabbelt <palmer@...osinc.com>,
        Conor Dooley <conor.dooley@...rochip.com>, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, heiko.stuebner@...ll.eu,
        Evan Green <evan@...osinc.com>, sunilvl@...tanamicro.com,
        linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 10/10] RISC-V: provide a Kconfig option to disable
 parsing "riscv,isa"

On Thu, Jun 29, 2023 at 10:44:18PM +0100, Conor Dooley wrote:
> On Thu, Jun 29, 2023 at 02:16:49PM -0700, Palmer Dabbelt wrote:
> > On Thu, 29 Jun 2023 13:20:55 PDT (-0700), Conor Dooley wrote:
...
> > > +bool __initdata riscv_isa_fallback_cmdline = false;
> > > +static int __init riscv_isa_fallback_setup(char *__unused)
> > 
> > Maybe it's better to support =true and =false here?  Not sure it matters,
> > we're already down a rabbit hole ;)
> 
> Dunno, not implemented a cmdline param before. Seemed "cleaner" to check
> for presence, don't really care so I'll adapt to w/e.
>

I don't have a strong preference here, but to throw in more food for
thought, I see this DT-v1 vs. DT-v2 choice to be a bit analogous to the
DT vs. ACPI choice. The 'acpi' command line parameter, for RISC-V, can
be 'off', 'on', and 'force', where

  off -- disable ACPI if default was on
  on -- enable ACPI but allow fallback to DT
  force -- enable ACPI if default was off

So, if the default of the isa fallback command line option will depend on
Kconfig, then we may also want a 'force'.

Thanks,
drew