This is a note to let you know that I've just added the patch titled

iio: addac: stx104: Fix race condition for stx104_write_raw()

to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the char-misc-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From 9740827468cea80c42db29e7171a50e99acf7328 Mon Sep 17 00:00:00 2001 From: William Breathitt Gray william.gray@linaro.org Date: Thu, 6 Apr 2023 10:40:10 -0400 Subject: iio: addac: stx104: Fix race condition for stx104_write_raw()

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 --- drivers/iio/addac/stx104.c | 8 ++++++++ 1 file changed, 8 insertions(+)

diff --git a/drivers/iio/addac/stx104.c b/drivers/iio/addac/stx104.c index e45b70aa5bb7..4239aafe42fc 100644 --- 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; }; @@ -178,9 +181,12 @@ 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; iowrite16(val, &priv->reg->dac[chan->channel]);

+ mutex_unlock(&priv->lock); return 0; } return -EINVAL; @@ -351,6 +357,8 @@ static int stx104_probe(struct device *dev, unsigned int id)

indio_dev->name = dev_name(dev);

+ mutex_init(&priv->lock); + /* configure device for software trigger operation */ iowrite8(0, &priv->reg->acr);