Re: [PATCH RESEND] spi: spidev: Allow matching DT compatible strings from ACPI

[Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>]

On Wed, Jun 29, 2016 at 07:31:01PM +0100, Mark Brown wrote:
> On Wed, Jun 29, 2016 at 07:34:20PM +0300, Mika Westerberg wrote:
> > On Wed, Jun 29, 2016 at 05:21:27PM +0100, Mark Brown wrote:
> 
> > > But can that compatible string be spidev and be matched via the paths DT
> > > uses while still ensuring that enough of the OF matching code is enabled
> > > to cause the check to warn?  That's the problem.
> 
> > No it can't. The match is done in ACPI code not in DT code. See
> > drivers/acpi/bus.c::acpi_of_match_device().
> 
> And we're *sure* that's going to be maintained?  People do use the
> fallback matching that DT does, I don't trust the ACPI maintainers not
> to do the same thing.

That fallback matching does not even work in ACPI like I told you
already. We have no plans to do anything like that either. That's the
reason why we complain if there is PRP0001 without compatible string.

> > > Life would be a lot eaiser if Intel would use DT where it's appropriate,
> > > or if the OF in ACPI stuff were more transparent and needed fewer
> > > special cases.
> 
> > I don't get this. We added PRP0001 and properties because then we can
> > reuse DT bindings in ACPI and thus there is no need to reinvent all
> > these things for ACPI.
> 
> Right, but rather than just define a translation from ACPI to DT and use
> the DT code paths in their entirety for the relevant nodes what's
> happening is that there's a shim layer between ACPI and DT which sort of
> emulates bits of the DT interfaces but not quite and can lead to
> surprises.

Maybe but currently it works fine. And if problems are found they will
be fixed as usual.
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