Re: [PATCH 05/11] dt-binding: Add ngpios property to GPIO controller node

[Ray Jui]

On 10/23/2015 6:02 AM, Laurent Pinchart wrote:
> Hi Rob,
>
> On Friday 23 October 2015 06:51:28 Rob Herring wrote:
> > On Fri, Oct 23, 2015 at 4:08 AM, Laurent Pinchart wrote:
> > > On Thursday 22 October 2015 18:41:05 Rob Herring wrote:
> > > > On Thu, Oct 22, 2015 at 1:52 PM, Ray Jui wrote:
> > > > > On 10/22/2015 11:43 AM, Rob Herring wrote:
> > > > > > On Mon, Oct 19, 2015 at 12:43 AM, Pramod Kumar wrote:
> > > > > > > Add ngpios property to the gpio controller's DT node so that
> > > > > > > controller driver extracts total number of gpio lines present in
> > > > > > > controller from DT and removes dependency on driver.
> > > > > > >
> > > > > > > Signed-off-by: Pramod Kumar <pramodku@xxxxxxxxxxxx>
> > > > > > > Reviewed-by: Ray Jui <rjui@xxxxxxxxxxxx>
> > > > > > > Reviewed-by: Scott Branden <sbranden@xxxxxxxxxxxx>
> > > > > > > ---
> > > > > > >
> > > > > > >   Documentation/devicetree/bindings/pinctrl/brcm,cygnus-gpio.txt | 5
> > > > > > >   +++
> > > > > > >   1 file changed, 5 insertions(+)
> > > > > > >
> > > > > > > diff --git
> > > > > > > a/Documentation/devicetree/bindings/pinctrl/brcm,cygnus-gpio.txt
> > > > > > > b/Documentation/devicetree/bindings/pinctrl/brcm,cygnus-gpio.txt
> > > > > > > index f92b833..655a8d7 100644
> > > > > > > --- a/Documentation/devicetree/bindings/pinctrl/brcm,cygnus-gpio.txt
> > > > > > > +++ b/Documentation/devicetree/bindings/pinctrl/brcm,cygnus-gpio.txt
> > > > > > >
> > > > > > > @@ -10,6 +10,9 @@ Required properties:
> > > > > > >        Define the base and range of the I/O address space that
> > > > > > >        contains
> > > > > > >
> > > > > > > the Cygnus
> > > > > > >
> > > > > > >    GPIO/PINCONF controller registers
> > > > > > >
> > > > > > > +- ngpios:
> > > > > > +    Total number of GPIOs the controller provides
> > > > > >
> > > > > > This must be optional for compatibility and the driver needs to handle
> > > > > > it not present.
> > > > >
> > > > > You meant to be compatible with existing Cygnus devices, correct?
> > > > >
> > > > > Just to clarify, here you suggest we still leave the existing hard
> > > > > coded ngpios in the driver, in order to be compatible with all existing
> > > > > Cygnus devices (while the Cygnus device tree changes to use ngpio is
> > > > > still being merged and through different maintainer), and have all new
> > > > > iProc SoCs switch to use ngpios from device tree, right?
> > > >
> > > > Yes, an existing dtb should continue to work with a new kernel. You
> > > > can add the DT property to the older devices too and then eventually
> > > > remove the hard coded values some time in the future. That could be
> > > > immediately (don't care about compatibility at all), a couple of
> > > > kernel cycles, never... It all depends on users of the impacted
> > > > platforms.
> > >
> > > But shouldn't the property still be documented as required to ensure that
> > > new DTs always include it ?
> >
> > Good point. If the intent is to eventually remove it from the driver,
> > then yes. We probably need "required for new designs" as a category or
> > maybe "recommended"? The wording is not so important here, but I'm
> > thinking about as we try to standardize the naming.
>
> Required for new designs sounds better than recommended. Or maybe something
> like "Required (optional for backward compatibility)".

Yes, it should be phrased as "required for new designs" because all new 
iProc SoCs using this GPIO driver need to have this in DT.

Thanks,

Ray
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