linux-kernel - Re: Enabling pmbus power control

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Date:   Mon, 19 Apr 2021 23:00:25 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Zev Weiss <zev@...ilderbeest.net>
Cc:     Mark Brown <broonie@...nel.org>, Jean Delvare <jdelvare@...e.com>,
        linux-hwmon@...r.kernel.org, Andrew Jeffery <andrew@...id.au>,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-kernel@...r.kernel.org, openbmc@...ts.ozlabs.org
Subject: Re: Enabling pmbus power control

On 4/19/21 10:50 PM, Zev Weiss wrote:
[ ... ]

> I had a glance at the enclosure driver; it looks pretty geared toward SES-like things (drivers/scsi/ses.c being its only usage I can see in the kernel at the moment) and while it could perhaps be pressed into working for this it seems like it would probably drag in a fair amount of boilerplate and result in a somewhat gratuitously confusing driver arrangement (calling the things involved in the cases we're looking at "enclosures" seems like a bit of a stretch).
> 
> As an alternative, would something like the patch below be more along the lines of what you're suggesting?  And if so, would it make sense to generalize it into something like 'pmbus-switch.c' and add a PMBUS_HAVE_POWERSWITCH functionality bit or similar in the pmbus code instead of hardcoding it for only LM25066 support?
> 
> 

No. Don't access pmbus functions from outside drivers/hwmon/pmbus.

I used to be opposed to function export restrictions (aka export namespaces),
but you are making a good case that we need to introduce them for pmbus
functions.

Guenter