[PATCH 3/3] lib: sbi_ecall: Add Kconfig option for each extension

[Andrew Jones]

On Tue, Oct 11, 2022 at 12:34:45AM +0800, Vivian Wang wrote:
> For each SBI extension, we:
> 
> - Add a Kconfig option for it
> - Add the extension to sbi_ecall_exts only if the extension is enabled
> - Add the corresponding sbi_ecall_* object file only if the extension is
>   enabled
> 
> Special cases are as follows:
> 
> - The legacy extensions are lumped together as one 'big' extension, as
>   has always been the case in OpenSBI code.
> - The platform-defined vendor extensions are regarded as one extension.
> - The Base extension cannot be disabled.
> - sbi_ecall_replace implements multiple extensions, so it's not easy to
>   avoid linking it in. Enable it always, and use #ifdef to
>   disable/enable individual extensions.

It's tempting to use this as an opportunity to break sbi_ecall_replace up
into different files, but I'm not sure it's worth it.