linux-kernel - Re: lm90 driver no longer working on PCs in 3.13

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Message-ID: <52E580CE.8080100@roeck-us.net>
Date:	Sun, 26 Jan 2014 13:40:30 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Mark Brown <broonie@...nel.org>, Jean Delvare <khali@...ux-fr.org>
CC:	LM Sensors <lm-sensors@...sensors.org>,
	linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
	Wei Ni <wni@...dia.com>
Subject: Re: lm90 driver no longer working on PCs in 3.13

On 01/26/2014 01:22 PM, Mark Brown wrote:
> On Sun, Jan 26, 2014 at 09:49:36PM +0100, Jean Delvare wrote:
>> On Sun, 26 Jan 2014 12:44:38 -0800, Guenter Roeck wrote:
>
>>> Maybe there is some configuration option, or maybe something needs to be
>>> configured from user space. I found neither.
>
>> Neither would be acceptable to my eyes anyway. Things worked out of the
>> box before, they should keep working out of the box.
>
> They only worked with a debug option turned on and generated warnings
> every time they were used...  that kernel config would've been actively
> broken for devices that wanted to do anything at all interesting with
> the regulators and would've been prone to issues with init ordering and
> races in any cases where there are actually regulators.
>
>>> Another possible fix would be to have the regulator core return -ENODEV
>>> instead of -EPROBE_DEFER on non-dt systems. No idea if this would be acceptable
>>> or even feasible.
>
>> Well, either the regulator subsystem gets fixed (or provides a suitable
>> API for drivers like lm90 and we update the lm90 driver to use it), or
>> I'll just revert the problematic commit for now. This is a severe
>> regression, we just can't leave things that way.
>
> It's not an issue in the driver, it's an issue in the combination of the
> platform and the kernel config.  If the regulator API is going to be
> turned on for the platform then either the platform needs to configure
> the supplies or it needs to tell the regulator core that it's safe to
> start using dummy regulators.
>
> What is this platform and why does it have the regulator API enabled in
> the first place?
>

It is a PC running Ubuntu. you'd have to ask the distro maintainers why they
turn on regulators.

config-3.8.0-26-generic:CONFIG_REGULATOR=y
config-3.8.0-35-generic:CONFIG_REGULATOR=y
config-3.11.0-13-generic:CONFIG_REGULATOR=y

Guenter

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