linux-kernel - Re: [PATCH 1/2] regulator: core: Add a sanity check on the regulator

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Date:	Tue, 06 Jan 2015 13:26:28 +0100
From:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
To:	Mark Brown <broonie@...nel.org>
CC:	Liam Girdwood <lgirdwood@...il.com>, linux-kernel@...r.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	Lior Amsalem <alior@...vell.com>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>, linux-ide@...r.kernel.org
Subject: Re: [PATCH 1/2] regulator: core: Add a sanity check on the regulator_
 enable/disable functions

Hi Mark,

On 06/01/2015 13:00, Mark Brown wrote:
> On Tue, Jan 06, 2015 at 12:36:02PM +0100, Gregory CLEMENT wrote:
>> Hi Mark,
>>
>> On 29/12/2014 16:40, Mark Brown wrote:
>>> On Fri, Dec 26, 2014 at 06:26:38PM +0100, Gregory CLEMENT wrote:
> 
>>> No, especially in the case of regulator_enable() this is deliberate -
>>> we're trying to ensure that if people are using regulators they're being
>>> careful about it, checking error codes and so on.  I'd really want to
> 
>> OK so at least we should check that the pointer is not NULL before using it
>> and inform the user of it by using a WARNING() or even a BUG() instead of
>> just let the kernel crash latter.
> 
> Just crashing on the NULL is just about as good in terms of
> discoverabilty and any consumer that is assuming NULL is not a valid
> regulator is buggy in any case, any non-error pointer could be a valid
> regulator as far as users are concerned.  
> 
>>> see some persuasive use case for this.  What you're saying here sounds
>>> like the consumer shouldn't be treating the regulator as optional at
>>> all but should instead be using a normal regulator.
> 
>> Being able to deal with NULL pointer in the disable function is convenient
>> and is done in other similar subsystems such as phy or clk for example. Instead
>> of having a check on the NULL pointer in each driver, it seems more logical to
>> do it directly in the disable function.
> 
> This really only applies if it's likely that some thing that always gets
> used if it's there might be missing which isn't the case for regulators,
> it's not at all common to have power supplies that might be missing and

Well the pattern the following pattern is very common in the drivers using
the regulator:

if (!IS_ERR(regulator_pointer)
	regulator_disable(regulator_pointer);


So for me it was a good hint that we can factorize it.

> if they are missing NULL isn't a good way to track them.
> 
> If you're having problems with this and need workarounds in the core to
> make your driver code look OK that sounds like things are working since
> it sounds like the driver code is probably abusing the API here.

I don't _need_ it at all. It was just an improvement but if you don't want it,
I am fine with it.


Thanks,

Gregory




-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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