[PATCH 2/5] iio: adc: palmas_gpadc: Replace indio_dev->mlock with own device lock

Mircea Caprioru
2020-09-28T13:14:21Z

From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>

As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock on the device's state structure.

This is part of a bigger cleanup.
Link: https://lore.kernel.org/linux-iio/CA+U=Dsoo6YABe5ODLp+eFNPGFDjk5ZeQEceGkqjxXcVEhLWubw@mail.gmail.com/

Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Mircea Caprioru <mircea.caprioru@analog.com>
---
drivers/iio/adc/palmas_gpadc.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/palmas_gpadc.c b/drivers/iio/adc/palmas_gpadc.c
index 889b88768b63..14874f11614d 100644
--- a/drivers/iio/adc/palmas_gpadc.c
+++ b/drivers/iio/adc/palmas_gpadc.c
@@ -90,6 +90,12 @@ static struct palmas_gpadc_info palmas_gpadc_info[] = {
* 3: 800 uA
* @extended_delay: enable the gpadc extended delay mode
* @auto_conversion_period: define the auto_conversion_period
+ * @lock: Lock to protect the device state during a potential concurrent
+ * read access from userspace. Reading a raw value requires a sequence
+ * of register writes, then a wait for a completion callback,
+ * and finally a register read, during which userspace could issue
+ * another read request. This lock protects a read access from
+ * ocurring before another one has finished.
*
* This is the palmas_gpadc structure to store run-time information
* and pointers for this driver instance.
@@ -110,6 +116,7 @@ struct palmas_gpadc {
bool wakeup1_enable;
bool wakeup2_enable;
int auto_conversion_period;
+ struct mutex lock;
};

/*
@@ -388,7 +395,7 @@ static int palmas_gpadc_read_raw(struct iio_dev *indio_dev,
if (adc_chan > PALMAS_ADC_CH_MAX)
return -EINVAL;

- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&adc->lock);

switch (mask) {
case IIO_CHAN_INFO_RAW:
@@ -414,12 +421,12 @@ static int palmas_gpadc_read_raw(struct iio_dev *indio_dev,
goto out;
}

- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&adc->lock);
return ret;

out:
palmas_gpadc_read_done(adc, adc_chan);
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&adc->lock);

return ret;
}
@@ -516,6 +523,9 @@ static int palmas_gpadc_probe(struct platform_device *pdev)
adc->dev = &pdev->dev;
adc->palmas = dev_get_drvdata(pdev->dev.parent);
adc->adc_info = palmas_gpadc_info;
+
+ mutex_init(&adc->lock);
+
init_completion(&adc->conv_completion);
dev_set_drvdata(&pdev->dev, indio_dev);

--
2.25.1