linux-kernel - Re: [PATCH v2 2/3] dt-bindings: iio: io-channel-mux: Add property for settle time

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Message-ID: <CAL_JsqKPFnNsX6g2GWFaF3ntb7mfCt4+YxFtv_JfMt2mp1s+mg@mail.gmail.com>
Date:   Fri, 8 Oct 2021 14:13:25 -0500
From:   Rob Herring <robh@...nel.org>
To:     Peter Rosin <peda@...ntia.se>
Cc:     Vincent Whitchurch <vincent.whitchurch@...s.com>,
        kernel <kernel@...s.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] dt-bindings: iio: io-channel-mux: Add property for
 settle time

On Fri, Oct 8, 2021 at 10:27 AM Peter Rosin <peda@...ntia.se> wrote:
>
> On 2021-10-08 15:56, Vincent Whitchurch wrote:
> > On Fri, Oct 08, 2021 at 04:46:12AM +0200, Rob Herring wrote:
> >> On Thu, 07 Oct 2021 15:46:40 +0200, Vincent Whitchurch wrote:
> >>> Hardware may require some time for the muxed analog signals to settle
> >>> after the muxing is changed.  Allow this time to be specified in the
> >>> devicetree.
> >>>
> >>> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> >>> ---
> >>>  .../devicetree/bindings/iio/multiplexer/io-channel-mux.yaml  | 5 +++++
> >>>  1 file changed, 5 insertions(+)
> >>>
> >>
> >> Running 'make dtbs_check' with the schema in this patch gives the
> >> following warnings. Consider if they are expected or the schema is
> >> incorrect. These may not be new warnings.
> >
> > Yes, these are not new warnings.
> >
> >> Note that it is not yet a requirement to have 0 warnings for dtbs_check.
> >> This will change in the future.
> >>
> >> Full log is available here: https://patchwork.ozlabs.org/patch/1537724
> >>
> >>
> >> adc0mux: '#io-channel-cells' does not match any of the regexes: 'pinctrl-[0-9]+'
> >>      arch/arm/boot/dts/aspeed-bmc-ampere-mtjade.dt.yaml
> >>
> >> adc10mux: '#io-channel-cells' does not match any of the regexes: 'pinctrl-[0-9]+'
> >>      arch/arm/boot/dts/aspeed-bmc-ampere-mtjade.dt.yaml
> > [...]
> >
> > I think the fix for these is to add a "#io-channel-cells": const 1 to
> > the schema.
>
> Agreed.
>
> >> envelope-detector-mux: channels: ['', '', 'sync-1', 'in', 'out', 'sync-2', 'sys-reg', 'ana-reg'] has non-unique elements
> >>      arch/arm/boot/dts/at91-tse850-3.dt.yaml
> >
> > This one looks like an error in that particular devicetree.
> >
> The double '' is intentional; this mux is 8-way but only 6 legs are
> connected, with the first two unused. I don't know how or where to make
> changes to dodge the warning. I don't want to put names on things that
> do not exist, and the iio-mux driver is using empty names as a hint to
> not configure any child channel for those indices that have empty names.
> If e.g. channels 0-5 are in use, then this is not a problem since you
> can just end early with 6 names instead of 8, but alas, channels 2-7
> was what the hw-crowd fancied in this case.

There's a specific string type for this: non-unique-string-array

Unfortunately, no way to say unique or empty strings.

Rob