staging: iio: resolver: ad2s1210: add debugfs reg access

This add an implementation of debugfs_reg_access for the AD2S1210
driver.
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20230929-ad2s1210-mainline-v3-11-fa4364281745@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/resolver/ad2s1210.c

@@ -614,9 +614,29 @@ static int ad2s1210_initial(struct ad2s1210_state *st)
 	return ret;
 }
 
+static int ad2s1210_debugfs_reg_access(struct iio_dev *indio_dev,
+				       unsigned int reg, unsigned int writeval,
+				       unsigned int *readval)
+{
+	struct ad2s1210_state *st = iio_priv(indio_dev);
+	int ret;
+
+	mutex_lock(&st->lock);
+
+	if (readval)
+		ret = regmap_read(st->regmap, reg, readval);
+	else
+		ret = regmap_write(st->regmap, reg, writeval);
+
+	mutex_unlock(&st->lock);
+
+	return ret;
+}
+
 static const struct iio_info ad2s1210_info = {
 	.read_raw = ad2s1210_read_raw,
 	.attrs = &ad2s1210_attribute_group,
+	.debugfs_reg_access = &ad2s1210_debugfs_reg_access,
 };
 
 static int ad2s1210_setup_clocks(struct ad2s1210_state *st)