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

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Date:	Thu, 08 Aug 2013 11:30:30 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Guenter Roeck <linux@...ck-us.net>
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 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.
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