linux-kernel - Re: [PATCH 1/1] riscv: default to CONFIG_RISCV_SBI

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Message-ID: <611d4055-c50c-55c1-0e02-43ffda66dbce@canonical.com>
Date:   Fri, 17 Dec 2021 11:42:27 +0100
From:   Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
To:     Jessica Clarke <jrtc27@...c27.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] riscv: default to CONFIG_RISCV_SBI_V01=n



On 12/16/21 17:51, Jessica Clarke wrote:
> On 16 Dec 2021, at 14:17, Heinrich Schuchardt <heinrich.schuchardt@...onical.com> wrote:
>>
>> On 12/16/21 14:49, Jessica Clarke wrote:
>>> On 16 Dec 2021, at 12:35, Heinrich Schuchardt <heinrich.schuchardt@...onical.com> wrote:
>>>>
>>>> The SBI 0.1 specification is obsolete. The current version is 0.3.
>>>> Hence we should not rely by default on SBI 0.1 being implemented.
>>> It’s what BBL implements, and some people are still using it,
>>> especially given early hardware shipped before OpenSBI grew in
>>> popularity.
>>> Jess
>>
>> Do you mean BBL is not developed anymore?
>>
>> Some people may still be using a 0.1 SBI. But that minority stuck on an outdated software stack does not justify defaulting to deprecated settings in future Linux releases.
> 
> BBL is still actively maintained; its most recent commit was 24 days
> ago. Also, the amount of code CONFIG_RISCV_SBI_V01 affects is tiny, so
> I see no tangible benefit from making this change, just unnecessary
> breakage of perfectly functional systems.

Only the default is changed. How could this break any existing system?
You can still compile with the deprecated setting.

I can not see why we should keep a default that will cause issues on 
systems complying to the current SBI specification.

Best regards

Heinrich