linux-kernel - Re: [PATCH] iio: addac: ad74413: don't set DIN_SINK for functions other than digital input

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Message-ID: <822d2741-32ff-fc73-28a5-25575ab3cc52@rasmusvillemoes.dk>
Date:   Mon, 22 May 2023 10:44:11 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Nuno Sá <noname.nuno@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Cosmin Tanislav <cosmin.tanislav@...log.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: addac: ad74413: don't set DIN_SINK for functions
 other than digital input

On 06/05/2023 20.16, Jonathan Cameron wrote:
> On Thu, 4 May 2023 12:08:53 +0200
> Rasmus Villemoes <linux@...musvillemoes.dk> wrote:
> 
>> On 04/05/2023 09.28, Nuno Sá wrote:

>>> Can anyone have a working device by specifying that dt parameter
>>> on a non digital channel (or expect something from having that parameter set)?
>>> Or the only effect is to actually have some functions misbehaving?  
>>
>> The data sheet doesn't say that the DIN_SINK should have any effect for
>> other functions, so I'm pretty sure it's only the latter: some functions
>> misbehave.
>>
>>> On the driver side, if it's never right to have
>>> these settings together, then the patch is valid since if someone has this, his
>>> configuration is broken anyways (maybe that's also a valid point for the
>>> bindings)...  
>>
>> Yes, I do believe that it's a broken description (whether or not the
>> bindings specify that), and drivers don't need to go out of their way to
>> validate or fixup such brokenness. But in this particular case, there's
>> really no extra burden on the driver to not put garbage in DIN_SINK when
>> a not-digital-input function has been chosen (the patch is a two-liner
>> with 'git show -w').
> 
> If we can tighten the DT binding to rule out something that should not be
> set than that would be good.  Tightening bindings is fine - we don't mind
> validation of bindings failing on peoples DTs as long as we didn't 'break'
> them actually working.

Well, I'm afraid I don't have any idea how to spell that constraint in
the yaml-language (help appreciated).

And I assume a dt binding update would be a separate patch anyway, so
could you please consider applying this patch?

Thanks,
Rasmus