Re: [PATCH v2] docs: specify stability of hypfs path documentation

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.07.2020 12:31, Jürgen Groß wrote:
> On 16.07.20 12:11, Jan Beulich wrote:
>> On 15.07.2020 16:37, George Dunlap wrote:
>>> IT sounds like you’re saying:
>>>
>>> 1. Paths listed without conditions will always be available
>>>
>>> 2. Paths listed with conditions may be extended: i.e., a node currently 
>>> listed as PV might also become available for HVM guests
>>>
>>> 3. Paths listed with conditions might have those conditions reduced, but 
>>> will never entirely disappear.  So something currently listed as PV might 
>>> be reduced to CONFIG_HAS_FOO, but won’t be completely removed.
>>>
>>> Is that what you meant?
>>
>> I see Jürgen replied "yes" to this, but I'm not sure about 1.
>> above: I think it's quite reasonable to expect that paths without
>> condition may gain a condition. Just like paths now having a
>> condition and (perhaps temporarily) losing it shouldn't all of
>> the sudden become "always available" when they weren't meant to
>> be.
>>
>> As far a 3. goes, I'm also unsure in how far this is any better
>> stability wise (from a consumer pov) than allowing paths to
>> entirely disappear.
> 
> The idea is that any user tool using hypfs can rely on paths under 1 to
> exist, while the ones under 3 might not be there due to the hypervisor
> config or the used system.
> 
> A path not being allowed to entirely disappear ensures that it remains
> in the documentation, so the same path can't be reused for something
> different in future.

And then how do you deal with a condition getting dropped, and
later wanting to get re-added? Do we need a placeholder condition
like [ALWAYS] or [TRUE]?

Jan