From: William Breathitt Gray <william.gray@xxxxxxxxxx>
commit 9740827468cea80c42db29e7171a50e99acf7328 upstream.
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: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/iio/addac/stx104.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/drivers/iio/addac/stx104.c
+++ b/drivers/iio/addac/stx104.c
@@ -15,6 +15,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
+#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/types.h>
@@ -69,10 +70,12 @@ struct stx104_reg {
/**
* struct stx104_iio - IIO device private data structure
+ * @lock: synchronization lock to prevent I/O race conditions
* @chan_out_states: channels' output states
* @reg: I/O address offset for the device registers
*/
struct stx104_iio {
+ struct mutex lock;
unsigned int chan_out_states[STX104_NUM_OUT_CHAN];
struct stx104_reg __iomem *reg;
};
@@ -182,9 +185,12 @@ static int stx104_write_raw(struct iio_d
if ((unsigned int)val > 65535)
return -EINVAL;
+ mutex_lock(&priv->lock);
+
priv->chan_out_states[chan->channel] = val;
iowrite16(val, &priv->reg->dac[chan->channel]);
+ mutex_unlock(&priv->lock);
return 0;
}
return -EINVAL;
@@ -355,6 +361,8 @@ static int stx104_probe(struct device *d
indio_dev->name = dev_name(dev);
+ mutex_init(&priv->lock);
+
/* configure device for software trigger operation */
iowrite8(0, &priv->reg->acr);
