[PATCH v2 01/16] iio: adc: ad799x: do not use internal iio_dev lock

Nuno Sá
2022-10-04T13:50:22Z

'mlock' was being grabbed when setting the device frequency. In order to
not introduce any functional change a new lock is added. With that in
mind, the lock also needs to be grabbed in the places where 'mlock' is
since it was also being used to protect st->config against the current
device state.

On the other places the lock was being used, we can just drop
it since we are only doing one i2c bus read/write which is already
safe.

While at it, properly include "mutex.h" for mutex related APIs.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
---
drivers/iio/adc/ad799x.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
index 262bd7665b33..44f7a80a0749 100644
--- a/drivers/iio/adc/ad799x.c
+++ b/drivers/iio/adc/ad799x.c
@@ -28,6 +28,7 @@
#include <linux/types.h>
#include <linux/err.h>
#include <linux/module.h>
+#include <linux/mutex.h>
#include <linux/bitops.h>

#include <linux/iio/iio.h>
@@ -125,6 +126,8 @@ struct ad799x_state {
const struct ad799x_chip_config *chip_config;
struct regulator *reg;
struct regulator *vref;
+ /* lock to protect against multiple access to the device */
+ struct mutex lock;
unsigned id;
u16 config;

@@ -290,7 +293,9 @@ static int ad799x_read_raw(struct iio_dev *indio_dev,
ret = iio_device_claim_direct_mode(indio_dev);
if (ret)
return ret;
+ mutex_lock(&st->lock);
ret = ad799x_scan_direct(st, chan->scan_index);
+ mutex_unlock(&st->lock);
iio_device_release_direct_mode(indio_dev);

if (ret < 0)
@@ -351,7 +356,8 @@ static ssize_t ad799x_write_frequency(struct device *dev,
if (ret)
return ret;

- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&st->lock);
+
ret = i2c_smbus_read_byte_data(st->client, AD7998_CYCLE_TMR_REG);
if (ret < 0)
goto error_ret_mutex;
@@ -373,7 +379,7 @@ static ssize_t ad799x_write_frequency(struct device *dev,
ret = len;

error_ret_mutex:
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&st->lock);

return ret;
}
@@ -407,6 +413,8 @@ static int ad799x_write_event_config(struct iio_dev *indio_dev,
if (ret)
return ret;

+ mutex_lock(&st->lock);
+
if (state)
st->config |= BIT(chan->scan_index) << AD799X_CHANNEL_SHIFT;
else
@@ -418,6 +426,7 @@ static int ad799x_write_event_config(struct iio_dev *indio_dev,
st->config &= ~AD7998_ALERT_EN;

ret = ad799x_write_config(st, st->config);
+ mutex_unlock(&st->lock);
iio_device_release_direct_mode(indio_dev);
return ret;
}
@@ -454,11 +463,9 @@ static int ad799x_write_event_value(struct iio_dev *indio_dev,
if (val < 0 || val > GENMASK(chan->scan_type.realbits - 1, 0))
return -EINVAL;

- mutex_lock(&indio_dev->mlock);
ret = i2c_smbus_write_word_swapped(st->client,
ad799x_threshold_reg(chan, dir, info),
val << chan->scan_type.shift);
- mutex_unlock(&indio_dev->mlock);

return ret;
}
@@ -473,10 +480,8 @@ static int ad799x_read_event_value(struct iio_dev *indio_dev,
int ret;
struct ad799x_state *st = iio_priv(indio_dev);

- mutex_lock(&indio_dev->mlock);
ret = i2c_smbus_read_word_swapped(st->client,
ad799x_threshold_reg(chan, dir, info));
- mutex_unlock(&indio_dev->mlock);
if (ret < 0)
return ret;
*val = (ret >> chan->scan_type.shift) &
@@ -863,6 +868,9 @@ static int ad799x_probe(struct i2c_client *client,
if (ret)
goto error_cleanup_ring;
}
+
+ mutex_init(&st->lock);
+
ret = iio_device_register(indio_dev);
if (ret)
goto error_cleanup_ring;
--
2.37.3