linux-kernel - Re: [RFC PATCH] dt-bindings: iio: adc: use spi-peripheral-props.yaml

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <72e30e5f-bc65-5176-2e60-f94f71a710d3@linaro.org>
Date:   Thu, 21 Jul 2022 11:38:18 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Rob Herring <robh@...nel.org>, Jonathan Cameron <jic23@...nel.org>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Alexandru Tachici <alexandru.tachici@...log.com>,
        Marcelo Schmitt <marcelo.schmitt1@...il.com>,
        Marcus Folkesson <marcus.folkesson@...il.com>,
        Kent Gustavsson <kent@...oris.se>,
        Tomislav Denis <tomislav.denis@....com>,
        Stefan Popa <stefan.popa@...log.com>,
        Beniamin Bia <beniamin.bia@...log.com>,
        Patrick Vasseur <patrick.vasseur@....fr>,
        Vladimir Barinov <vladimir.barinov@...entembedded.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Philippe Reynes <tremyfr@...oo.fr>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Akinobu Mita <akinobu.mita@...il.com>,
        Alexandru Lazar <alazar@...rtmail.com>,
        Oskar Andero <oskar.andero@...il.com>,
        Mårten Lindahl <martenli@...s.com>,
        Bogdan Pricop <bogdan.pricop@...tex.com>,
        Angelo Compagnucci <angelo.compagnucci@...il.com>,
        Dan Murphy <dmurphy@...com>, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fbdev@...r.kernel.org, linux-spi@...r.kernel.org,
        Mark Brown <broonie@...nel.org>
Subject: Re: [RFC PATCH] dt-bindings: iio: adc: use spi-peripheral-props.yaml

On 19/07/2022 00:00, Rob Herring wrote:
> On Sat, Jul 16, 2022 at 07:26:04PM +0100, Jonathan Cameron wrote:
>> On Fri, 15 Jul 2022 11:53:02 +0200
>> Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
>>
>>> Instead of listing directly properties typical for SPI peripherals,
>>> reference the spi-peripheral-props.yaml schema.  This allows using all
>>> properties typical for SPI-connected devices, even these which device
>>> bindings author did not tried yet.
>>>
>>> Remove the spi-* properties which now come via spi-peripheral-props.yaml
>>> schema, except for the cases when device schema adds some constraints
>>> like maximum frequency.
>>>
>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>>
>>> ---
>>>
>>> This is an RFC with only some files changed, as I am still not sure of
>>> benefits for typical case - device node has just spi-max-frequency and
>>> nothing more.  I still find useful to reference the schema, but maybe I
>>> am missing something?
>>>
>>> Before doing wide-tree cleanup like this, I would be happy to receive
>>> some feedback whether this makes sense.
>>
>> Hi Krzysztof,
>>
>> This has the side effect of allowing spi-cpol / spi-cpha for devices
>> where they weren't previously allowed by the binding.  A typical device
>> only supports a subset of combinations of those.
>>
>> I'm not clear whether these should always be allowed (e.g. allow for inverters
>> etc in the path) or whether we should be enforcing the "correct"
>> settings for devices assuming they are directly connected.
>>
>> Currently we have a bunch of bindings that are documenting the allowed
>> flexibility - including cases where only particular combinations of these
>> settings are allowed.
>>
>> So we could either:
>> 1) Note that we've been doing it wrong and the binding should not enforce
>>    these constraints so remove them.
> 
> I'd lean towards this.
> 
>> 2) Add explicit spi-cpol: false statements etc the drivers where they
>>    are not allowed.
> 
> 3) Drop spi-cpol / spi-cpha from spi-peripheral-props.yaml. It's purpose 
> is to collect all possible SPI controller properties that are per child 
> node. Whereas we've said spi-cpol / spi-cpha are device specific 
> properties.

Thanks Rob and Jonathan. I can go with (3).

Best regards,
Krzysztof