linux-kernel - Re: [PATCH v3 1/2] hwmon: (lm90) Add power control

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Message-ID: <522F35BF.6070909@wwwdotorg.org>
Date:	Tue, 10 Sep 2013 09:07:43 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Mark Brown <broonie@...nel.org>
CC:	Guenter Roeck <linux@...ck-us.net>, Wei Ni <wni@...dia.com>,
	"khali@...ux-fr.org" <khali@...ux-fr.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] hwmon: (lm90) Add power control

On 09/10/2013 04:09 AM, Mark Brown wrote:
> On Mon, Sep 09, 2013 at 10:13:56PM -0600, Stephen Warren wrote:
>> On 09/09/2013 09:53 PM, Guenter Roeck wrote:
> 
>>> Earlier comments suggest that this is not the intended use case
>>> for regulator_get_optional().
> 
> That's right.
> 
>> Isn't the issue only whether the optional aspect of the regulator
>> is implemented by:
> 
>> a) regulator_get_optional() returning failure, then the driver
>> having to check for that and either using or not-using the
>> regulator.
> 
>> b) regulator_get_optional() returning a dummy regulator
>> automatically when none is specified in DT or the regulator
>> lookup table, and hence the driver can always call
>> regulator_enable/disable on the returned value.
> 
> No.  There are a couple of issues here.  One is that we don't want
> to litter all drivers with conditional code to check if they
> actually got the regulator and so on, that's just pointless make
> work on the part of consumers.

So that's exactly the difference between (a) and (b) above.

> The other is that just ignoring errors is generally terrible 
> practice which we don't want to encourage - ignoring the specific
> case where nothing is provided and the system has control of that
> is one thing but just ignoring any error is another.

Yes, obviously the code somewhere needs to distinguish between
missing-so-use-a-dummy, and specified-but-in-a-broken-way. Doesn't
regulator_get_optional() already distinguish those two cases? Perhaps
that's the enhancement to regulator_get_optional() that you were
requesting.

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