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

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Date:	Sun, 26 Jan 2014 13:50:40 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Jean Delvare <khali@...ux-fr.org>
CC:	LM Sensors <lm-sensors@...sensors.org>,
	linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.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 12:49 PM, Jean Delvare wrote:
> On Sun, 26 Jan 2014 12:44:38 -0800, Guenter Roeck wrote:
>> On 01/26/2014 12:13 PM, Jean Delvare wrote:
>> The regulator code changed with 3.13; the dummy regulator no longer exists,
>> and the functionality it provided is supposed to be handled automatically.
>> But that only really works on devicetree based systems and otherwise returns
>> -EPROBE_DEFER as mentioned above.
>>
>> 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.
>
>> In the first case, we should create
>> a dependency for the LM90 driver; in the latter case, we would have to make sure
>> that it is well documented (I'd grumble on that, though - it would result in
>> never ending trouble for us, having to repeatedly explain how this is now
>> supposed to work).
>>
>> 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.
>

Maybe your configuration has CONFIG_REGULATORS disabled. Ubuntu has it enabled.
I don't know about others.

I agree, we may have to revert the patch. I don't think the regulator API works well
enough in non-dt systems to be able to use it in such systems. Mark's expectation
that regulator support must be disabled if regulators are not fully declared in non-dt
systems doesn't seem very useful nor really feasible.

Guenter

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