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Date: Tue, 22 Mar 2022 20:41:39 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Jagath Jog J <jagathjog1996@...il.com>
CC: Jonathan Cameron <jic23@...nel.org>, <dan@...obertson.com>,
<andy.shevchenko@...il.com>, <linux-iio@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/5] iio: accel: bma400: conversion to device-managed
function
On Tue, 22 Mar 2022 02:42:41 +0530
Jagath Jog J <jagathjog1996@...il.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@...il.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@...il.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@...obertson.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,
> > > };
> > >
> >
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