Re: [PATCH v1 1/5] iio: accel: bma400: conversion to device-managed function

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Tue, 22 Mar 2022 02:42:41 +0530
Jagath Jog J <jagathjog1996@gmail.com> wrote:

> On Sun, Mar 20, 2022 at 05:14:22PM +0000, Jonathan Cameron wrote:
> > On Sat, 19 Mar 2022 23:40:19 +0530
> > Jagath Jog J <jagathjog1996@gmail.com> wrote:
> >   
> > > This is a conversion to device-managed by using devm_iio_device_register
> > > inside probe function, now disabling the regulator and putting bma400 to
> > > power down via a devm_add_action_or_reset() hook.
> > > 
> > > The dev_set_drvdata() call, bma400_remove() function and hooks in the I2C
> > > and SPI driver struct is removed as devm_iio_device_register function is
> > > used to automatically unregister on driver detach.
> > > 
> > > Signed-off-by: Jagath Jog J <jagathjog1996@gmail.com>  
> > 
> > Hi Jagath,
> > 
> > There is an oddity in the existing driver that has lead this in
> > what I think is the wrong direction.  See below.
> >   
> > > ---
> > >  drivers/iio/accel/bma400.h      |  2 --
> > >  drivers/iio/accel/bma400_core.c | 39 ++++++++++++++-------------------
> > >  drivers/iio/accel/bma400_i2c.c  |  8 -------
> > >  drivers/iio/accel/bma400_spi.c  |  8 -------
> > >  4 files changed, 17 insertions(+), 40 deletions(-)
> > > 
> > > diff --git a/drivers/iio/accel/bma400.h b/drivers/iio/accel/bma400.h
> > > index c4c8d74155c2..e938da5a57b4 100644
> > > --- a/drivers/iio/accel/bma400.h
> > > +++ b/drivers/iio/accel/bma400.h
> > > @@ -94,6 +94,4 @@ extern const struct regmap_config bma400_regmap_config;
> > >  
> > >  int bma400_probe(struct device *dev, struct regmap *regmap, const char *name);
> > >  
> > > -void bma400_remove(struct device *dev);
> > > -
> > >  #endif
> > > diff --git a/drivers/iio/accel/bma400_core.c b/drivers/iio/accel/bma400_core.c
> > > index fd2647b728d3..dcc7549c7a0e 100644
> > > --- a/drivers/iio/accel/bma400_core.c
> > > +++ b/drivers/iio/accel/bma400_core.c
> > > @@ -793,6 +793,19 @@ static const struct iio_info bma400_info = {
> > >  	.write_raw_get_fmt = bma400_write_raw_get_fmt,
> > >  };
> > >  
> > > +static void bma400_disable(void *data_ptr)
> > > +{
> > > +	struct bma400_data *data = data_ptr;
> > > +	int ret;
> > > +
> > > +	ret = bma400_set_power_mode(data, POWER_MODE_SLEEP);
> > > +	if (ret)
> > > +		dev_warn(data->dev, "Failed to put device into sleep mode (%pe)\n",
> > > +			 ERR_PTR(ret));
> > > +
> > > +	regulator_bulk_disable(ARRAY_SIZE(data->regulators), data->regulators);  
> > 
> > So this raised alarm bells.  You almost never want a devm callback to do two things.
> > 
> > The reason it 'looks' like this might be ok is that the driver is currently calling
> > bma400_set_power_mode(data, POWER_MODE_SLEEP) in error paths during probe.
> > I think it should be.  If you make that modification first you'll see that to
> > keep a clean: "only undo things you have done" approach you'll then need
> > to have a pair of devm_add_action_or_reset() callbacks so as to cover the
> > disabling of the regulators when the power enabling fails and then to
> > cover the change to sleep mode if anything else fails.  
> 
> Sure I will add separate functions for regulators disable and power disable
> then use them with help of two devm_add_action_or_reset() callbacks in bma400_init
> function. Is below is correct?
> 
> static void bma400_regulators_disable(void *data_ptr)
> {
>         struct bma400_data *data = data_ptr;
> 
>         regulator_bulk_disable(ARRAY_SIZE(data->regulators), data->regulators);
> }
> 
> static void bma400_power_disable(void *data_ptr)
> {
>         struct bma400_data *data = data_ptr;
>         int ret;
> 
>         mutex_lock(&data->mutex);
>         ret = bma400_set_power_mode(data, POWER_MODE_SLEEP);
>         if (ret)
>                 dev_warn(data->dev, "Failed to put device into sleep mode (%pe)\n",
>                          ERR_PTR(ret));
>         mutex_unlock(&data->mutex);
> }
> 
> static int bma400_init(struct bma400_data *data)
> {
>         unsigned int val;
>         int ret;
> 
> ......
> 
>        ret = regulator_bulk_enable(ARRAY_SIZE(data->regulators),
>                                     data->regulators);
>         if (ret) {
>                 dev_err(data->dev, "Failed to enable regulators: %d\n",
>                         ret);
>                 goto out;
>         }
> 
>         ret = devm_add_action_or_reset(data->dev, bma400_regulators_disable, data);
>         if (ret)
> 		return ret;
> 
> ...
> 
>         if (data->power_mode != POWER_MODE_NORMAL) {
>                 ret = bma400_set_power_mode(data, POWER_MODE_NORMAL);
>                 if (ret) {
>                         dev_err(data->dev, "Failed to wake up the device\n");
>                         goto err_reg_disable;
>                 }
>                 /*
>                  * TODO: The datasheet waits 1500us here in the example, but
>                  * lists 2/ODR as the wakeup time.
>                  */
>                 usleep_range(1500, 2000);
>         }
> 
>         ret = devm_add_action_or_reset(data->dev, bma400_power_disable, data);
>         if (ret)
> 		return ret;
> ....
> 
>         return regmap_write(data->regmap, BMA400_ACC_CONFIG2_REG, 0x00);
> 
> err_reg_disable:
>         regulator_bulk_disable(ARRAY_SIZE(data->regulators),
>                                data->regulators);

No route to these error paths any more. So drop this.

Otherwise looks good to me.



> out:
Note an out label is always a bad thing.  Just return directly
instead of goto out;

Thanks,

Jonathan

>         return ret;
> }
> 
> > 
> > 
> > Jonathan
> >   
> > > +}
> > > +
> > >  int bma400_probe(struct device *dev, struct regmap *regmap, const char *name)
> > >  {
> > >  	struct iio_dev *indio_dev;
> > > @@ -822,31 +835,13 @@ int bma400_probe(struct device *dev, struct regmap *regmap, const char *name)
> > >  	indio_dev->num_channels = ARRAY_SIZE(bma400_channels);
> > >  	indio_dev->modes = INDIO_DIRECT_MODE;
> > >  
> > > -	dev_set_drvdata(dev, indio_dev);
> > > -
> > > -	return iio_device_register(indio_dev);
> > > -}
> > > -EXPORT_SYMBOL(bma400_probe);
> > > -
> > > -void bma400_remove(struct device *dev)
> > > -{
> > > -	struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > > -	struct bma400_data *data = iio_priv(indio_dev);
> > > -	int ret;
> > > -
> > > -	mutex_lock(&data->mutex);
> > > -	ret = bma400_set_power_mode(data, POWER_MODE_SLEEP);
> > > -	mutex_unlock(&data->mutex);
> > > -
> > > +	ret = devm_add_action_or_reset(dev, bma400_disable, data);
> > >  	if (ret)
> > > -		dev_warn(dev, "Failed to put device into sleep mode (%pe)\n", ERR_PTR(ret));
> > > -
> > > -	regulator_bulk_disable(ARRAY_SIZE(data->regulators),
> > > -			       data->regulators);
> > > +		return ret;
> > >  
> > > -	iio_device_unregister(indio_dev);
> > > +	return devm_iio_device_register(dev, indio_dev);
> > >  }
> > > -EXPORT_SYMBOL(bma400_remove);
> > > +EXPORT_SYMBOL(bma400_probe);
> > >  
> > >  MODULE_AUTHOR("Dan Robertson <dan@dlrobertson.com>");
> > >  MODULE_DESCRIPTION("Bosch BMA400 triaxial acceleration sensor core");
> > > diff --git a/drivers/iio/accel/bma400_i2c.c b/drivers/iio/accel/bma400_i2c.c
> > > index f50df5310beb..56da06537562 100644
> > > --- a/drivers/iio/accel/bma400_i2c.c
> > > +++ b/drivers/iio/accel/bma400_i2c.c
> > > @@ -27,13 +27,6 @@ static int bma400_i2c_probe(struct i2c_client *client,
> > >  	return bma400_probe(&client->dev, regmap, id->name);
> > >  }
> > >  
> > > -static int bma400_i2c_remove(struct i2c_client *client)
> > > -{
> > > -	bma400_remove(&client->dev);
> > > -
> > > -	return 0;
> > > -}
> > > -
> > >  static const struct i2c_device_id bma400_i2c_ids[] = {
> > >  	{ "bma400", 0 },
> > >  	{ }
> > > @@ -52,7 +45,6 @@ static struct i2c_driver bma400_i2c_driver = {
> > >  		.of_match_table = bma400_of_i2c_match,
> > >  	},
> > >  	.probe    = bma400_i2c_probe,
> > > -	.remove   = bma400_i2c_remove,
> > >  	.id_table = bma400_i2c_ids,
> > >  };
> > >  
> > > diff --git a/drivers/iio/accel/bma400_spi.c b/drivers/iio/accel/bma400_spi.c
> > > index 9f622e37477b..96dc9c215401 100644
> > > --- a/drivers/iio/accel/bma400_spi.c
> > > +++ b/drivers/iio/accel/bma400_spi.c
> > > @@ -87,13 +87,6 @@ static int bma400_spi_probe(struct spi_device *spi)
> > >  	return bma400_probe(&spi->dev, regmap, id->name);
> > >  }
> > >  
> > > -static int bma400_spi_remove(struct spi_device *spi)
> > > -{
> > > -	bma400_remove(&spi->dev);
> > > -
> > > -	return 0;
> > > -}
> > > -
> > >  static const struct spi_device_id bma400_spi_ids[] = {
> > >  	{ "bma400", 0 },
> > >  	{ }
> > > @@ -112,7 +105,6 @@ static struct spi_driver bma400_spi_driver = {
> > >  		.of_match_table = bma400_of_spi_match,
> > >  	},
> > >  	.probe    = bma400_spi_probe,
> > > -	.remove   = bma400_spi_remove,
> > >  	.id_table = bma400_spi_ids,
> > >  };
> > >    
> >