iio: adc: ad7192: Grab direct mode for calibration

While a calibration is running, better don't make the device do anything
else.

To enforce that, grab direct mode during calibration.

Fixes: 42776c1 ("staging: iio: adc: ad7192: Add system calibration support")
Signed-off-by: Uwe Kleine-König <[email protected]>
Link: https://patch.msgid.link/8aade802afca6a89641e24c1ae1d4b8d82cff58d.1740655250.git.u.kleine-koenig@baylibre.com
Signed-off-by: Jonathan Cameron <[email protected]>

Author: ukleinek

drivers/iio/adc/ad7192.c

@@ -257,6 +257,9 @@ static ssize_t ad7192_write_syscalib(struct iio_dev *indio_dev,
 	if (ret)
 		return ret;
 
+	if (!iio_device_claim_direct(indio_dev))
+		return -EBUSY;
+
 	temp = st->syscalib_mode[chan->channel];
 	if (sys_calib) {
 		if (temp == AD7192_SYSCALIB_ZERO_SCALE)
@@ -267,6 +270,8 @@ static ssize_t ad7192_write_syscalib(struct iio_dev *indio_dev,
 					      chan->address);
 	}
 
+	iio_device_release_direct(indio_dev);
+
 	return ret ? ret : len;
 }