From: William Breathitt Gray william.gray@linaro.org
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@linaro.org Link: https://lore.kernel.org/r/c95c9a77fcef36b2a052282146950f23bbc1ebdc.168079058... Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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);