Re: [PATCH v2 2/6] RISC-V: Add a syscall for HW probing

Conor Dooley
2023-02-07T06:32:34Z

Hey Evan, Greg,

On 7 February 2023 06:13:39 GMT, Greg KH <gregkh@linuxfoundation.org> wrote:
>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.

https://lore.kernel.org/linux-riscv/20221201160614.xpomlqq2fzpzfmcm@kamzik/

This is the sysfs interface that I mentioned drew
suggested on the v1.
I think it fits ~perfectly with what Greg is suggesting too.

>
>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