Re: [PATCH v2 1/6] driver core: Move the "authorized" attribute from USB/Thunderbolt to core

[Dan Williams]

On Thu, Sep 30, 2021 at 12:50 PM Kuppuswamy, Sathyanarayanan
<sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote:
>
>
>
> On 9/30/21 12:04 PM, Dan Williams wrote:
> >>> That's why it was highlighted in the changelog. Hopefully a
> >>> Thunderbolt developer can confirm if it is a non-issue.
> >>> Documentation/ABI/testing/sysfs-bus-thunderbolt does not seem to
> >>> answer this question about whether authorized_show and
> >>> authorized_store need to be symmetric.
> >> Apparently, Bolt does read it [1] and cares about it [2].
> > Ah, thank you!
> >
> > Yeah, looks like the conversion to bool was indeed too hopeful.
> >
>
> IIUC, the end result of value "2" in authorized sysfs is to just
> "authorize" or "de-authorize". In that case, can the user space
> driver adapt to this int->bool change? Just want to know the
> possibility.

ABIs are forever. The kernel has to uphold its contract to bolt that
it will return '2' and not '1' after '2' has been written.