From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH v3 1/2] hwmon: (lm90) Add power control Date: Mon, 09 Sep 2013 21:40:30 -0600 Message-ID: <522E94AE.7000804@wwwdotorg.org> References: <1378722552-10357-1-git-send-email-wni@nvidia.com> <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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <522E93D6.2010304-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Guenter Roeck Cc: Wei Ni , Mark Brown , "khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org" , "lm-sensors-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org" , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-tegra@vger.kernel.org On 09/09/2013 09:36 PM, Guenter Roeck wrote: > On 09/09/2013 08:22 PM, Wei Ni wrote: >> On 09/09/2013 11:50 PM, Guenter Roeck wrote: >>> On Mon, Sep 09, 2013 at 02:50:22PM +0100, Mark Brown wrote: >>>> On Mon, Sep 09, 2013 at 04:34:43AM -0700, Guenter Roeck wrote: >>>>> On 09/09/2013 04:12 AM, Mark Brown wrote: >>>>>> On Mon, Sep 09, 2013 at 06:29:11PM +0800, Wei Ni wrote: >>>> >>>>>> This doesn't look good, it is going to ignore actual errors - I >>>>>> *really* >>>>>> doubt that vcc is optional, it looks like it's the main power >>>>>> supply for >>>>>> the device. You should use normal regulator_get(), _optional() is >>>>>> for >>>>>> supplies which could physically not be provided in a system (eg, >>>>>> if the >>>>>> device can generate them internally if required). >>>> >>>>> Then he'll have to make sure that all devicetree files in the system >>>>> contain references to this regulator. >>>> >>>> Or get the patches applied on top of the code that'll be going in this >>>> cycle implementing get_optional() properly - when that's done the >>>> default will be to provide a dummy supply for regulator_get(). If you >>>> ack the patch I'd be happy to carry it. >>>> >>> Jean will have to ack it. >>> >> I think it's better to use get_optional(), and ignore the errors except >> -EPROBE_DEFER. Because many platform may always power on this device, >> and will not provide regulator for it, so if we get errors from >> regulator subsystem and return it directly, then the probe() can't be >> implemented, this driver can't work properly, even though it can work >> without regulator support. >> Mark, do you mean you have patches for regulator_get_optional() and >> regulator_get()? >> > > My understanding is that by adding regulator support you essentially > committed to adding regulators (if necessary dummy ones) for this driver > to all those platforms. This is quite similar to other drivers in the > same situation. Once you start along that route, you'll have to go it > all the way. By using regulator_get_optional(), the regulator should be optional, hence you only have to add it to platforms that need it.