iio: adc: ad_sigma_delta: do not use internal iio_dev lock

commit 20228a1d5a55e7db0c6720840f2c7d2b48c55f69 upstream.

Drop 'mlock' usage by making use of iio_device_claim_direct_mode().
This change actually makes sure we cannot do a single conversion while
buffering is enable. Note there was a potential race in the previous
code since we were only acquiring the lock after checking if the bus is
enabled.

Fixes: af3008485ea0 ("iio:adc: Add common code for ADI Sigma Delta devices")
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: <Stable@vger.kernel.org> #No rush as race is very old.
Link: https://lore.kernel.org/r/20220920112821.975359-2-nuno.sa@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index 1d652d9..bd5c495 100644 (file)
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -280,10 +280,10 @@ int ad_sigma_delta_single_conversion(struct iio_dev *indio_dev,
        unsigned int data_reg;
        int ret = 0;
 
-       if (iio_buffer_enabled(indio_dev))
-               return -EBUSY;
+       ret = iio_device_claim_direct_mode(indio_dev);
+       if (ret)
+               return ret;
 
-       mutex_lock(&indio_dev->mlock);
        ad_sigma_delta_set_channel(sigma_delta, chan->address);
 
        spi_bus_lock(sigma_delta->spi->master);
@@ -322,7 +322,7 @@ out:
        ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);
        sigma_delta->bus_locked = false;
        spi_bus_unlock(sigma_delta->spi->master);
-       mutex_unlock(&indio_dev->mlock);
+       iio_device_release_direct_mode(indio_dev);
 
        if (ret)
                return ret;