[PATCH 4/5] iio: adc: vf610_adc: Replace indio_dev->mlock with own device lock

Mircea Caprioru
2020-09-28T13:14:27Z

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/vf610_adc.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
index 1d794cf3e3f1..b7d583993f0b 100644
--- a/drivers/iio/adc/vf610_adc.c
+++ b/drivers/iio/adc/vf610_adc.c
@@ -168,6 +168,15 @@ struct vf610_adc {

struct completion completion;
u16 buffer[8];
+ /*
+ * 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.
+ */
+ struct mutex lock;
};

static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
@@ -464,11 +473,11 @@ static int vf610_set_conversion_mode(struct iio_dev *indio_dev,
{
struct vf610_adc *info = iio_priv(indio_dev);

- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&info->lock);
info->adc_feature.conv_mode = mode;
vf610_adc_calculate_rates(info);
vf610_adc_hw_init(info);
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);

return 0;
}
@@ -632,9 +641,9 @@ static int vf610_read_raw(struct iio_dev *indio_dev,
switch (mask) {
case IIO_CHAN_INFO_RAW:
case IIO_CHAN_INFO_PROCESSED:
- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&info->lock);
if (iio_buffer_enabled(indio_dev)) {
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);
return -EBUSY;
}

@@ -645,11 +654,11 @@ static int vf610_read_raw(struct iio_dev *indio_dev,
ret = wait_for_completion_interruptible_timeout
(&info->completion, VF610_ADC_TIMEOUT);
if (ret == 0) {
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);
return -ETIMEDOUT;
}
if (ret < 0) {
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);
return ret;
}

@@ -668,11 +677,11 @@ static int vf610_read_raw(struct iio_dev *indio_dev,

break;
default:
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);
return -EINVAL;
}

- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);
return IIO_VAL_INT;

case IIO_CHAN_INFO_SCALE:
@@ -807,6 +816,9 @@ static int vf610_adc_probe(struct platform_device *pdev)
}

info = iio_priv(indio_dev);
+
+ mutex_init(&info->lock);
+
info->dev = &pdev->dev;

info->regs = devm_platform_ioremap_resource(pdev, 0);
--
2.25.1