Date:   Tue, 7 Feb 2023 07:13:39 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Evan Green <evan@rivosinc.com>
Cc:     Palmer Dabbelt <palmer@rivosinc.com>,
        Conor Dooley <conor@kernel.org>, vineetg@rivosinc.com,
        heiko@sntech.de, slewis@rivosinc.com,
        Albert Ou <aou@eecs.berkeley.edu>,
        Andrew Bresticker <abrestic@rivosinc.com>,
        Andrew Jones <ajones@ventanamicro.com>,
        Anup Patel <apatel@ventanamicro.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Atish Patra <atishp@rivosinc.com>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Celeste Liu <coelacanthus@outlook.com>,
        Conor Dooley <conor.dooley@microchip.com>,
        Dao Lu <daolu@rivosinc.com>, Guo Ren <guoren@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Ruizhe Pan <c141028@gmail.com>,
        Sunil V L <sunilvl@ventanamicro.com>,
        Tobias Klauser <tklauser@distanz.ch>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org
Subject: Re: [PATCH v2 2/6] RISC-V: Add a syscall for HW probing
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On Mon, Feb 06, 2023 at 12:14:51PM -0800, Evan Green wrote:
> We don't have enough space for these all in ELF_HWCAP{,2} and there's no
> system call that quite does this, so let's just provide an arch-specific
> one to probe for hardware capabilities.  This currently just provides
> m{arch,imp,vendor}id, but with the key-value pairs we can pass more in
> the future.

Ick, this is exactly what sysfs is designed to export in a sane way.
Why not just use that instead?  The "key" would be the filename, and the
value the value read from the filename.  If the key is not present, the
file is not present and it's obvious what is happening, no fancy parsing
and ABI issues at all.

Bonus is that you will also properly document all valid key/value pairs
in Documentation/ABI/ when you do this, so it reinforces what the code
should be doing correctly.

thanks,

greg k-h