linux-kernel - RE: [PATCH] dt-bindings: iio: admv1014: make all regs required

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Date:   Mon, 31 Jul 2023 10:16:34 +0000
From:   "Miclaus, Antoniu" <Antoniu.Miclaus@...log.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC:     Jonathan Cameron <jic23@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] dt-bindings: iio: admv1014: make all regs required


> -----Original Message-----
> From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Sent: Monday, July 31, 2023 1:13 PM
> To: Miclaus, Antoniu <Antoniu.Miclaus@...log.com>
> Cc: Jonathan Cameron <jic23@...nel.org>; Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org>; robh+dt@...nel.org;
> krzysztof.kozlowski+dt@...aro.org; conor+dt@...nel.org; linux-
> iio@...r.kernel.org; devicetree@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH] dt-bindings: iio: admv1014: make all regs required
> 
> [External]
> 
> On Mon, 31 Jul 2023 07:40:14 +0000
> "Miclaus, Antoniu" <Antoniu.Miclaus@...log.com> wrote:
> 
> > > -----Original Message-----
> > > From: Jonathan Cameron <jic23@...nel.org>
> > > Sent: Saturday, July 29, 2023 2:55 PM
> > > To: Miclaus, Antoniu <Antoniu.Miclaus@...log.com>
> > > Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>;
> > > robh+dt@...nel.org; krzysztof.kozlowski+dt@...aro.org;
> > > conor+dt@...nel.org; linux-iio@...r.kernel.org;
> > > devicetree@...r.kernel.org; linux-kernel@...r.kernel.org
> > > Subject: Re: [PATCH] dt-bindings: iio: admv1014: make all regs required
> > >
> > > [External]
> > >
> > > On Thu, 27 Jul 2023 12:02:04 +0000
> > > "Miclaus, Antoniu" <Antoniu.Miclaus@...log.com> wrote:
> > >
> > > > > -----Original Message-----
> > > > > From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> > > > > Sent: Thursday, July 27, 2023 2:47 PM
> > > > > To: Miclaus, Antoniu <Antoniu.Miclaus@...log.com>;
> jic23@...nel.org;
> > > > > robh+dt@...nel.org; krzysztof.kozlowski+dt@...aro.org;
> > > > > conor+dt@...nel.org; linux-iio@...r.kernel.org;
> > > > > devicetree@...r.kernel.org; linux-kernel@...r.kernel.org
> > > > > Subject: Re: [PATCH] dt-bindings: iio: admv1014: make all regs
> required
> > > > >
> > > > > [External]
> > > > >
> > > > > On 27/07/2023 13:31, Antoniu Miclaus wrote:
> > > > > > Since the regulators are required in the driver implementation,
> make
> > > > > > them required also in the bindings.
> > >
> > > This bit is probably not strictly true.  Try no providing them and you will
> > > probably find stub regulators created on assumption they are fixed regs
> > > that we aren't interested in controlling.
> > >
> > > > > >
> > > > >
> > > > > The true reason should be whether the hardware requires them.
> > > Because if
> > > > > hardware does not need some, the driver should be fixed.
> > > > The datasheet is not very explicit on this topic, but all the specifications
> of
> > > the
> > > > part are built around these pins being supplied.
> > > > Moreover, the evaluation board or the part comes with all VCC pins
> > > connected
> > > > to fixed supplies.
> > >
> > > Agreed - these should be required in the binding.
> > >
> > Hello Jonathan,
> >
> > Not sure if I fully understand. Should I drop this patch?
> 
> Patch is good.  The binding should state these are required - it doesn't
> mean that the driver will fail to probe on systems that doesn't provide
> them.  It does encourage any new DTS files to incorporate them which is
> good to have.
> 
> Only thing that needs changing is the patch should not justify the
> addition of these to the binding because they 'are required in the
> driver implementation'.  Just drop that statement and the patch is
> fine.
Great, thanks a lot for the clarification.
> 
> 
> 
> > And also drop the "required" of the regulators in the admv1013 patch?
> > https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-
> iio/patch/20230727110121.93546-1-
> antoniu.miclaus@...log.com/__;!!A3Ni8CS0y2Y!8dQigVuPYwGwS53vsq2RO
> CJx3RgfeZW4GZks5EFWhfUlJZTdAvsCr5MGlrWUVHXwqRKoASc4UBEFE8h6N
> KO6jrfSQ-oKjKtS$
> 
> As long as the patch doesn't say anything about what the driver does
> then it is fine.  Note DT bindings and patch descriptions for them should
> never mention the driver.
> 
> Jonathan
> 
> >
> > Thanks,
> > > There was an old disagreement on this in which it they were not marked
> > > required in some bindings because the regulator subsystem would
> assume
> > > they
> > > were fixed supplies that were just missing in the DT and so provides stub
> > > regulators.
> > > My understanding at least has changed and now we mark the required
> even
> > > if
> > > the driver works fine on some boards without them being supplied.
> > >
> > > Note though that this means the whole of trivial-devices.yaml is garbage
> > > as very few devices actually work without any power :)
> > >
> > > Jonathan
> > >
> > >
> > >
> > > > > Best regards,
> > > > > Krzysztof
> > > >
> >