On 08/08/2013 02:42 AM, Guenter Roeck wrote:

On 08/07/2013 11:56 PM, Wei Ni wrote:

quoted

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.

quoted

diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c

quoted

  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().

quoted

+    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.