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    SubjectRe: [PATCH v2 09/14] staging: iio: ad7746: Add remove()
    On Fri, 13 Apr 2018 13:36:46 -0300
    Hernán Gonzalez <hernan@vanguardiasur.com.ar> wrote:

    > This allows the driver to be probed and removed as a module powering it
    > down on remove().
    >
    > Signed-off-by: Hernán Gonzalez <hernan@vanguardiasur.com.ar>
    > ---
    > drivers/staging/iio/cdc/ad7746.c | 26 ++++++++++++++++++++++++++
    > 1 file changed, 26 insertions(+)
    >
    > diff --git a/drivers/staging/iio/cdc/ad7746.c b/drivers/staging/iio/cdc/ad7746.c
    > index c29a221..05506bf9 100644
    > --- a/drivers/staging/iio/cdc/ad7746.c
    > +++ b/drivers/staging/iio/cdc/ad7746.c
    > @@ -775,6 +775,31 @@ static int ad7746_probe(struct i2c_client *client,
    > return 0;
    > }
    >
    > +static int ad7746_remove(struct i2c_client *client)
    > +{
    > + struct iio_dev *indio_dev = i2c_get_clientdata(client);
    > + struct ad7746_chip_info *chip = iio_priv(indio_dev);
    > + unsigned char regval;
    > + int ret;
    > +
    > + mutex_lock(&chip->lock);
    > +
    > + regval = chip->config | AD7746_CONF_MODE_PWRDN;
    > + ret = i2c_smbus_write_byte_data(chip->client, AD7746_REG_CFG, regval);
    As this is a one off operation, perhaps it would be better to factor
    it out to a utility function then use devm_add_action_or_reset in
    the probe?

    Also, I am nervous about this change as there doesn't seem to be
    path in probe by which this is deliberately reversed?
    It seems to be 'accidentally' handled by the read_raw write to the
    CFG register.

    The data sheet doesn't really mention much about this register
    at all. It may have special requirements to exit from power down - I have
    no idea, but if it is costless, why do we bother with idle mode?

    Perhaps Michael can confirm if this is safe to do or not.


    > +
    > + mutex_unlock(&chip->lock);
    > +
    > + if (ret < 0) {
    > + dev_warn(&client->dev, "Could NOT Power Down!\n");
    > + goto out;
    > + }
    > +
    > + iio_device_unregister(indio_dev);
    You can't safely do this against the devm_iio_device_register.

    > +
    > +out:
    > + return ret;
    > +}
    > +
    > static const struct i2c_device_id ad7746_id[] = {
    > { "ad7745", 7745 },
    > { "ad7746", 7746 },
    > @@ -799,6 +824,7 @@ static struct i2c_driver ad7746_driver = {
    > .of_match_table = of_match_ptr(ad7746_of_match),
    > },
    > .probe = ad7746_probe,
    > + .remove = ad7746_remove,
    > .id_table = ad7746_id,
    > };
    > module_i2c_driver(ad7746_driver);

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