Re: [PATCH v2 1/5] dt-bindings: add bindings for i2c-pca-platform

From: Rob Herring
Date: Fri Jun 23 2017 - 17:41:50 EST

On Thu, Jun 22, 2017 at 09:20:59PM +0000, Chris Packham wrote:
> On 22/06/17 20:23, Wolfram Sang wrote:
> >
> >> + - reset-gpios : gpio specifier for gpio connected to RESET_N pin.
> >
> > What about the 'active' state that Rob mentioned in his last review?
> >
> My intention was that by saying it is connected to the RESET_N bin the
> active state is covered.

I would say okay, but based on below it's not.

> I personally always get a little confused when talking about reset
> lines. The _N denotes that the line is active low but because it is a
> reset line writing 1 releases the reset so from a what-the-user-wants
> perspective it's active high.
> dt-binding-wise what we want here is GPIO_ACTIVE_HIGH, as in the driver
> writes 1 to release reset so don't do any polarity inversion. I'd be
> happy do add something to that effect in a v3 but I actually felt saying
> the gpio is connected to RESET_N was less ambiguous.

No, the driver is wrong. The binding should say GPIO_ACTIVE_LOW because
that is how the pin is defined. The driver needs to set it to inactive.