linux-kernel - Re: [PATCH v2 1/3] hwmon: (lm90) Add power control

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Date:	Thu, 8 Aug 2013 10:59:32 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Wei Ni <wni@...dia.com>, khali@...ux-fr.org,
	MLongnecker@...dia.com, linux-arm-kernel@...ts.infradead.org,
	lm-sensors@...sensors.org, linux-kernel@...r.kernel.org,
	linux-tegra@...r.kernel.org
Subject: Re: [PATCH v2 1/3] hwmon: (lm90) Add power control

On Thu, Aug 08, 2013 at 11:30:30AM -0600, Stephen Warren wrote:
> On 08/08/2013 02:42 AM, Guenter Roeck wrote:
> > On 08/07/2013 11:56 PM, Wei Ni wrote:
> >> The device lm90 can be controlled by the vdd rail.
> >> Adding the power control support to power on/off the vdd rail.
> >> And make sure that power is enabled before accessing the device.
> 
> >> diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
> 
> >>   static int lm90_probe(struct i2c_client *client,
> >>                 const struct i2c_device_id *id)
> >>   {
> >> @@ -1406,6 +1434,20 @@ static int lm90_probe(struct i2c_client *client,
> >>       i2c_set_clientdata(client, data);
> >>       mutex_init(&data->update_lock);
> >>
> >> +    data->lm90_reg = regulator_get(&client->dev, "vdd");
> > 
> > You should use devm_regulator_get(). Then you also don't need the call
> > to regulator_put().
> > 
> >> +    if (IS_ERR_OR_NULL(data->lm90_reg)) {
> > 
> > The function never returns NULL except if the regulator subsystem is not
> > configured,
> > so IS_ERR() is more appropriate.
> > 
> > If the regulator subsystem is not configured, you especially don't need
> > or want
> > to pollute the log with an error message.
> 
> DT parsing errors should be reported. However, if there's nothing to
> parse, it's not an error.
> 
> So, I think this should report an error message *if* there is a DT
> property that defines the regulator to use. If there's no property, just
> use no regulator. If there is a property, it had better be possible to
> parse it.
> 
Agreed.

Guenter
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