Re: [PATCH v2 1/3] x86/boot: add acpi rsdp address to setup_header

[Juergen Gross]

On 08/12/17 09:48, Ingo Molnar wrote:
> 
> * Juergen Gross <jgross@xxxxxxxx> wrote:
> 
>>>> +Offset/size:	0x268/8
>>>> +Protocol:	2.14+
>>>> +
>>>> +  This field can be set by the boot loader to tell the kernel the
>>>> +  physical address of the ACPI RSDP table.
>>>> +
>>>> +  A value of 0 indicates the kernel should fall back to the standard
>>>> +  methods to locate the RSDP (search in EBDA/low memory).
>>>
>>> That's not the only method used: the ACPI RSDP address can also be discovered via 
>>> efi.rsdp20 and efi.rsdp, both of which appear to be 32-bit values.
>>
>> Sure, but this is valid for booting via EFI only.
> 
> Yeah, so what I tried to say is that the description as written is not fully 
> correct and triggered my pedantry:
> 
>  +  A value of 0 indicates the kernel should fall back to the standard
>  +  methods to locate the RSDP (search in EBDA/low memory).
> 
> To make it correct we need to either write less:
> 
>  +  A value of 0 indicates the kernel should fall back to the standard
>  +  methods to locate the RSDP.
> 
> or write more and make it open ended so it doesn't have to be extended with every 
> method of getting the RSDP that might be added in the future:
> 
>  +  A value of 0 indicates the kernel should fall back to the standard
>  +  methods to locate the RSDP (search in EBDA/low memory, get it from
>  +  EFI if present, etc.).
> 
> ... or so?

Aah, okay. I got your remark wrong then.

I think I'll go with the shorter variant.


Juergen