Hi Bjorn,
On Fri, Dec 4, 2015 at 10:26 PM, Bjorn Helgaas <[email protected]> wrote:
> On Tue, Dec 01, 2015 at 04:24:30PM +0900, Simon Horman wrote:
>> Simply document new compat strings.
>> There appears to be no need for a driver updates.
>>
>> Signed-off-by: Simon Horman <[email protected]>
>> ---
>> Documentation/devicetree/bindings/pci/pci-rcar-gen2.txt | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/Documentation/devicetree/bindings/pci/pci-rcar-gen2.txt
>> b/Documentation/devicetree/bindings/pci/pci-rcar-gen2.txt
>> index b19be08a8113..7c231b3e5872 100644
>> --- a/Documentation/devicetree/bindings/pci/pci-rcar-gen2.txt
>> +++ b/Documentation/devicetree/bindings/pci/pci-rcar-gen2.txt
>> @@ -8,6 +8,7 @@ OHCI and EHCI controllers.
>> Required properties:
>> - compatible: "renesas,pci-r8a7790" for the R8A7790 SoC;
>> "renesas,pci-r8a7791" for the R8A7791 SoC;
>> + "renesas,pci-r8a7793" for the R8A7793 SoC;
>
> What's the benefit of adding a string here if the driver doesn't check
> for it? Since the driver doesn't look for it, there's no way to test
> anything.
If we ever discover a difference between PCI on r8a7793 compared to PCI on
other SoCs of the R-Car Gen2 family, we can handle that difference in the
driver.
> It doesn't seem like this file is an authoritative source of names, so
Yes it is. When adding compatible values to a DTS, checkpatch.pl will check
for their existence in the binding documentation. Hence we always add the
compatible values to the DT binding docs, before we start using them.
> if we add it here, there's the possibility the r8a7793 will be
> canceled or renamed, and then we'd have to update this if the driver
> ever did need an r8a7793-specific quirk. If we waited until the
I don't understand what you mean here.
> driver actually needs a quirk, then we'd know exactly what name to
> look for and we could update the driver, DT, and doc all together.
If we update driver, DT, and doc only after we discover the need for a quirk,
it's already too late, due to stable DT rules. Hence we always document and
use SoC-specific compatible values, sometimes combined with family-specific
compatible values. The driver only matches to the as least specific value as
possible.
I hope this clears up your worries.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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