[PATCH] iio: adc: ad_sigma_delta: Fix use of uninitialized variable status_pos

[Purva Yeshi <purvayeshi550@gmail.com>]

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Fix Smatch-detected error:
drivers/iio/adc/ad_sigma_delta.c:604 ad_sd_trigger_handler() error:
uninitialized symbol 'status_pos'.

The variable `status_pos` was only initialized in specific switch cases
(1, 2, 3, 4), which could leave it uninitialized if `reg_size` had an
unexpected value.

Fix by validating `reg_size` before the switch block. If it’s not
one of the expected values, return early and log an error. This ensures
`status_pos` is always initialized before use and prevents undefined
behavior.

Signed-off-by: Purva Yeshi <purvayeshi550@gmail.com>
---
 drivers/iio/adc/ad_sigma_delta.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index 6c37f8e21120..d3b59d90b728 100644
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -568,6 +568,11 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
 	else
 		transfer_size = reg_size;
 
+	if (reg_size != 1 && reg_size != 2 && reg_size != 3 && reg_size != 4) {
+		dev_err(&indio_dev->dev, "Unsupported reg_size: %u\n", reg_size);
+		return IRQ_HANDLED;
+	}
+
 	switch (reg_size) {
 	case 4:
 	case 2:
-- 
2.34.1