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

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Date:	Mon, 9 Sep 2013 12:12:42 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Wei Ni <wni@...dia.com>
Cc:	khali@...ux-fr.org, linux@...ck-us.net, swarren@...dotorg.org,
	lm-sensors@...sensors.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] hwmon: (lm90) Add power control

On Mon, Sep 09, 2013 at 06:29:11PM +0800, Wei Ni wrote:

> +	reg = devm_regulator_get_optional(dev, "vcc");
> +	if (!IS_ERR(reg)) {
> +		err = regulator_enable(reg);
> +		if (err < 0) {
> +			dev_err(&client->dev,
> +				"Failed to enable regulator: %d\n", err);
> +			return err;
> +		}
> +		msleep(25);
> +	} else {
> +		if (PTR_ERR(reg) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +	}

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).

Also do you really need 25ms after power on?

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