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Date: Mon, 09 Sep 2013 20:53:50 -0700 From: Guenter Roeck <linux@...ck-us.net> To: Stephen Warren <swarren@...dotorg.org> CC: Wei Ni <wni@...dia.com>, Mark Brown <broonie@...nel.org>, "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 09/09/2013 08:40 PM, Stephen Warren wrote: > 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. > Earlier comments suggest that this is not the intended use case for regulator_get_optional(). Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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