iio: adc: max1027: Prevent single channel accesses during buffer reads

When hardware buffers are enabled (the cnvst pin being the trigger), one
should not mess with the device state by requesting a single channel
read.

There is already a iio_buffer_enabled() check in *_read_single_value()
to merely prevent this situation but the check is inconsistent since
buffers can be enabled after the if clause anyway. Instead, use the core
mutex by calling iio_device_claim/release_direct_mode().

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20210921115408.66711-11-miquel.raynal@bootlin.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
index 33f89f902b8361efed0adace045119964eb3923e..a3ab88bbe5ae9bbd6a99fb1ae30d7e2ac13a3bf8 100644 (file)
--- a/drivers/iio/adc/max1027.c
+++ b/drivers/iio/adc/max1027.c
@@ -311,10 +311,9 @@ static int max1027_read_single_value(struct iio_dev *indio_dev,
        int ret;
        struct max1027_state *st = iio_priv(indio_dev);
 
-       if (iio_buffer_enabled(indio_dev)) {
-               dev_warn(&indio_dev->dev, "trigger mode already enabled");
-               return -EBUSY;
-       }
+       ret = iio_device_claim_direct_mode(indio_dev);
+       if (ret)
+               return ret;
 
        /* Configure conversion register with the requested chan */
        st->reg = MAX1027_CONV_REG | MAX1027_CHAN(chan->channel) |
@@ -325,6 +324,7 @@ static int max1027_read_single_value(struct iio_dev *indio_dev,
        if (ret < 0) {
                dev_err(&indio_dev->dev,
                        "Failed to configure conversion register\n");
+               iio_device_release_direct_mode(indio_dev);
                return ret;
        }
 
@@ -337,6 +337,9 @@ static int max1027_read_single_value(struct iio_dev *indio_dev,
 
        /* Read result */
        ret = spi_read(st->spi, st->buffer, (chan->type == IIO_TEMP) ? 4 : 2);
+
+       iio_device_release_direct_mode(indio_dev);
+
        if (ret < 0)
                return ret;