From: William Breathitt Gray <william.gray@xxxxxxxxxx>
[ Upstream commit 9740827468cea80c42db29e7171a50e99acf7328 ]
The priv->chan_out_states array and actual DAC value can become
mismatched if stx104_write_raw() is called concurrently. Prevent such a
race condition by utilizing a mutex.
Fixes: 97a445dad37a ("iio: Add IIO support for the DAC on the Apex Embedded Systems STX104")
Signed-off-by: William Breathitt Gray <william.gray@xxxxxxxxxx>
Link: https://lore.kernel.org/r/c95c9a77fcef36b2a052282146950f23bbc1ebdc.1680790580.git.william.gray@xxxxxxxxxx
Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/iio/adc/stx104.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/iio/adc/stx104.c b/drivers/iio/adc/stx104.c
index 2da741d27540f..edc3b29eed621 100644
--- a/drivers/iio/adc/stx104.c
+++ b/drivers/iio/adc/stx104.c
@@ -23,6 +23,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
+#include <linux/mutex.h>
#include <linux/spinlock.h>
#define STX104_OUT_CHAN(chan) { \
@@ -54,10 +55,12 @@ MODULE_PARM_DESC(base, "Apex Embedded Systems STX104 base addresses");
/**
* struct stx104_iio - IIO device private data structure
+ * @lock: synchronization lock to prevent I/O race conditions
* @chan_out_states: channels' output states
* @base: base port address of the IIO device
*/
struct stx104_iio {
+ struct mutex lock;
unsigned int chan_out_states[STX104_NUM_OUT_CHAN];
unsigned int base;
};
@@ -160,9 +163,12 @@ static int stx104_write_raw(struct iio_dev *indio_dev,
if ((unsigned int)val > 65535)
return -EINVAL;
+ mutex_lock(&priv->lock);
+
priv->chan_out_states[chan->channel] = val;
outw(val, priv->base + 4 + 2 * chan->channel);
+ mutex_unlock(&priv->lock);
return 0;
}
return -EINVAL;
@@ -323,6 +329,8 @@ static int stx104_probe(struct device *dev, unsigned int id)
priv = iio_priv(indio_dev);
priv->base = base[id];
+ mutex_init(&priv->lock);
+
/* configure device for software trigger operation */
outb(0, base[id] + 9);
--
2.43.0
