linux-kernel - Re: [PATCH v2 2/3] hwmon: (pmbus/core): Add regulator event support

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Date:   Mon, 10 Apr 2023 07:40:36 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Matti Vaittinen <mazziesaccount@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Naresh Solanki <naresh.solanki@...ements.com>,
        linux-hwmon@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        linux-kernel@...r.kernel.org, Sascha Hauer <sha@...gutronix.de>,
        jerome Neanne <jneanne@...libre.com>,
        "Mutanen, Mikko" <Mikko.Mutanen@...rohmeurope.com>
Subject: Re: [PATCH v2 2/3] hwmon: (pmbus/core): Add regulator event support

On 4/10/23 01:19, Matti Vaittinen wrote:
> to 6. huhtik. 2023 klo 16.43 Mark Brown (broonie@...nel.org) kirjoitti:
>>
>> On Thu, Apr 06, 2023 at 11:00:02AM +0300, Matti Vaittinen wrote:
>>> ke 5. huhtik. 2023 klo 18.19 Mark Brown (broonie@...nel.org) kirjoitti:
>>>> On Wed, Apr 05, 2023 at 07:18:32AM -0700, Guenter Roeck wrote:
> 
>>>> It can also try to avoid
>>>> interacting with hardware if that might not work.
>>
>>> It'd be great to have documentation / specification for sending and/or
>>> handling the regulator events. I don't think we currently have such.
>>> As far as I understand, the notifications can be picked up by all
>>> consumers of a regulator. I am a bit worried about:
>>> a) Situations where notification handlers 'collide' by doing 'actions'
>>> which are unexpected by other handlers
>>
>> I'm not sure what you're expecting there?  A device working with itself
>> shouldn't disrupt any other users.
> 
> I have no concrete idea, just a vague uneasy feeling knowing that
> devices tend to interact with each other. I guess it is more about the
> amount of uncertainty caused by my lack of knowledge regarding what
> could be done by these handlers. So, as I already said - if no one
> else is bothered by this then I definitely don't want to block the
> series. Still, if the error handling should be kept internal to PMBus
> - then we should probably either say that consumer drivers must not
> (forcibly) turn off the supply when receiving these notifications - or
> not send these notifications from PMBus and allow PMBus to decide
> error handling internally. (Again, I don't know if any in-tree
> consumer drivers do turn off the supply regulator in error handlers -
> but I don't think it is actually forbidden). Or am I just making  a
> problem that does not exist?
> 

For my part I (still) don't understand why this is considered a problem
for this driver but not for all the other drivers reporting various
error conditions to the regulator subsystem. At least some of them
also have programmable reaction to such error conditions.

Guenter