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

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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: 97a445dad3 ("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.1680790580.git.william.gray@linaro.org
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
William Breathitt Gray 2023-04-06 10:40:10 -04:00 committed by Jonathan Cameron
parent 86fb8b3aeb
commit 9740827468
1 changed files with 8 additions and 0 deletions
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8
drivers/iio/addac/stx104.c
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@ -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);