Re: [PATCH v3 06/17] hw/sd/sdcard: Do not store vendor data on block drive (CMD56)

[Fabiano Rosas]

Peter Xu <peterx@redhat.com> writes:

> On Thu, Jul 11, 2024 at 10:34:12AM -0300, Fabiano Rosas wrote:
>> Is there an easy way to look at a field and tell in which machine type's
>> timeframe it was introduced?
>
> I am not aware of any.
>
>> If the machine type of that era has been removed, then the field is free
>> to go as well. I'd prefer if we had a hard link instead of just counting
>> years. Maybe we should to that mapping at the machine deprecation time?
>> As in, "look at the unused fields introduced in that timeframe and mark
>> them free".
>
> We can do that, but depending on how easy it would be. That can be an
> overkill to me if it's non-trivial.  When it becomes complicated, I'd
> rather make machine compat property easier to use so we always stick with
> that.  Currently it's not as easy to use.
>
> Maybe we shouldn't make it a common rule to let people reuse the UNUSED
> fields, even if in this case it's probably fine?
>
> E.g. I don't think it's a huge deal to keep all UNUSED fields forever -
> sending 512B zeros for only one specific device isn't an issue even if kept
> forever.
>
> If "over 6 years" would be okay and simple enough, then maybe we can stick
> with that (and only if people would like to reuse a field and ask; that's
> after all not required..).  If more than that I doubt whether we should
> spend time working on covering all the fields.

I'm fine with a simple rule.

But of course, that means we cannot claim to support all kinds of
forward migrations anymore. Only those in the 6 year period.