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Date: Tue, 22 Mar 2022 02:42:41 +0530
From: Jagath Jog J <jagathjog1996@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: 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 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);
out:
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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