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

Arnd Bergmann
2023-02-15T09:57:28Z

On Mon, Feb 6, 2023, at 21:14, 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.
>
> Co-developed-by: Palmer Dabbelt <palmer@rivosinc.com>
> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> Signed-off-by: Evan Green <evan@rivosinc.com>

I'm not sure I understand the problem with
AT_HWCAP. While the bits in AT_HWCAP and AT_HWCAP2
are limited, I don't see us running out of new
AT_* words to use for additional bits. Presumably
the kernel would already have to know about the
name of each supported HW feature and could assign
a unique bit number to them.

Arnd