Message-ID: <522F35BF.6070909@wwwdotorg.org>
Date: Tue, 10 Sep 2013 09:07:43 -0600
From: Stephen Warren <swarren@wwwdotorg.org>
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To: Mark Brown <broonie@kernel.org>
CC: Guenter Roeck <linux@roeck-us.net>, Wei Ni <wni@nvidia.com>,
        "khali@linux-fr.org" <khali@linux-fr.org>,
        "lm-sensors@lm-sensors.org" <lm-sensors@lm-sensors.org>,
        "linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 1/2] hwmon: (lm90) Add power control
References: <1378722552-10357-2-git-send-email-wni@nvidia.com> <20130909111242.GW29403@sirena.org.uk> <522DB253.6000707@roeck-us.net> <20130909135022.GZ29403@sirena.org.uk> <20130909155043.GA18975@roeck-us.net> <522E9059.3070305@nvidia.com> <522E93D6.2010304@roeck-us.net> <522E94AE.7000804@wwwdotorg.org> <522E97CE.4070300@roeck-us.net> <522E9C84.9070405@wwwdotorg.org> <20130910100939.GW29403@sirena.org.uk>
In-Reply-To: <20130910100939.GW29403@sirena.org.uk>
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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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