Re: [PATCH v2 0/7] Change snvs rtc and poweroff to use syscon add pwrkey driver

[Russell King - ARM Linux <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>]

On Wed, May 20, 2015 at 07:25:41PM +0100, Russell King - ARM Linux wrote:
> On Wed, May 20, 2015 at 09:58:51AM +0800, Shawn Guo wrote:
> > On Wed, May 20, 2015 at 01:04:35AM +0800, Frank.Li-KZfg59tc24xl57MIdRCFDg@public.gmane.org wrote:
> > > Frank Li (6):
> > >   arm: imx: power-off: change to syscon to access register
> > >   rtc: arm: imx: snvs: change use syscon to access register
> > >   Document: dt: fsl: snvs: change support syscon
> > >   arm: dts: imx: update snvs to use syscon access register
> > >   document: devicetree: input: imx: i.mx snvs power device tree bindings
> > >   arm: dts: imx6sx: enable snvs power key
> > 
> > So, the series will break existing DTBs for RTC and poweroff, right?
> > If this is unavoidable, should we at least have some warning messages
> > telling users about his breakage?
> 
> What's the justification for breaking existing DTBs?  Really, this is
> something we should strive to avoid, _and_ actually avoid by providing
> backwards compatibility.

Looking at the RTC code, it would be pretty trivial to do.

Rather than passing around struct regmap, pass around the private data
structure.

Rename the regmap_* function calls to be private accessors.  Implement
a set of new accessors - if the private data has the regmap, use the
regmap API.  Otherwise, use the old method, and print a warning that an
old DT is being used.

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