[FFmpeg-devel] [PATCH] libavutil/riscv: Make use of elf_aux_info() on FreeBSD / OpenBSD riscv

[Brad Smith]

On 2024-11-18 1:28 p.m., Rémi Denis-Courmont wrote:
> Le maanantaina 18. marraskuuta 2024, 4.02.39 EET Brad Smith a écrit :
>> libavutil/riscv: Make use of elf_aux_info() on FreeBSD / OpenBSD riscv
>>
>> FreeBSD/OpenBSD riscv have elf_aux_info().
> Does OpenBSD use the same HWCAP encoding as Linux and FreeBSD?

Yes. All of the relevant bits were copied as is from FreeBSD and the feature
flags are the same between all of them.

> On real contemporary commercial hardware, there are two CPU configurations that
> affect FFmpeg, on top of the baseline RV64GC/RVA20:
> - StarFive JH7110: Zba and Zbb,
> - Canaan K230 and SpacemiT K1: Zba, Zbb, Zbs and V (or RVA22 + V).
>
> The first one simply can't be handled with this encoding scheme which leaves no
> room for extension without single letter designation.
>
> The second one won't be detected properly unless the kernel understands that B
> is equivalent to Zba, Zbb and Zbs (or the device tree is manually patched). It
> seems that at least FreeBSD fails there:https://reviews.freebsd.org/D46277

I wasn't aware of that. My consideration for this was for the eventual 
Vector support.

Thanks for pointing out the diff. I'll see about bringing that in as a 
start.