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

[Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>]

On Thu, Jun 30, 2016 at 03:49:31PM +0300, Mika Westerberg wrote:
> On Wed, Jun 29, 2016 at 08:20:59PM +0100, Mark Brown wrote:
> > On Wed, Jun 29, 2016 at 09:51:55PM +0300, Mika Westerberg wrote:
> > > On Wed, Jun 29, 2016 at 07:31:01PM +0100, Mark Brown wrote:
> > 
> > > > 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.
> > 
> > No, you're completely missing the point here.  The problem is someone
> > using something like linux,spidev as a compatible string and going into
> > fallback matching on SPI bus IDs rather than compatible strings.  I just
> > don't have confidence that someone isn't going to try to add that
> > fallback path given that it's used for DT.
> 
> If someone is using "linux,spidev" as compatible string it will not
> match anything and we are not going to add any kind of fallback to the
> ACPI core for that.
> 
> Of course we cannot predict what happens in the future but is it really
> preventing merging of this patch?
> 
> What I'm simply trying to achieve is to use the existing two DT
> compatible strings from ACPI. I've tested that it works fine and
> provided you all the evidence that it does not break the check for
> misusing DT.

Actually there seems to be alternative to this.

Windows seems to have a similar spidev raw interface in their MITT test
suite here:

https://msdn.microsoft.com/fi-fi/windows/hardware/drivers/spb/spi-tests-in-mitt

It exposes three ACPI SPI devices with ACPI IDs of SPT0001, SPT0002 and
SPT0003. I'm thinking that instead of using the existing DT compatible
strings we could use these ACPI IDs in the driver.
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