linux-kernel - Re: [lm-sensors] lm90 driver no longer working on PCs in 3.13

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Date:	Sun, 26 Jan 2014 14:04:06 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Jean Delvare <khali@...ux-fr.org>
CC:	Liam Girdwood <lgirdwood@...il.com>, Wei Ni <wni@...dia.com>,
	Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
	LM Sensors <lm-sensors@...sensors.org>
Subject: Re: [lm-sensors] lm90 driver no longer working on PCs in 3.13

On 01/26/2014 01:50 PM, Guenter Roeck wrote:
> 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.
>

I think I have a better idea: Surround the regulator code, or at least its error handling,
in the lm90 driver with
	if (IS_ENABLED(CONFIG_OF)) {
	}

Would that be ok ? If yes I'll submit a patch. I'll do the same in another driver
I am working on.

Guenter

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