ASoC: bcm63xx-pcm-whistler: fix uninit-value in i2s_dma_isr

Fix an issue detected by the Smatch tool:

sound/soc/bcm/bcm63xx-pcm-whistler.c:264 i2s_dma_isr()
error: uninitialized symbol 'val_1'.
sound/soc/bcm/bcm63xx-pcm-whistler.c:264 i2s_dma_isr()
error: uninitialized symbol 'val_2'.

These errors were triggered because the variables 'val_1' and 'val_2'
could remain uninitialized if 'offlevel' is zero, meaning the loop
that assigns values to them does not execute. In this case,
'dma_addr_next' would use uninitialized data, potentially leading
to undefined behavior.

To resolve this, a conditional update for 'dma_addr_next' is added,
ensuring it is assigned only when 'val_1' and 'val_2' are read.
A new boolean variable 'val_read' flags when the values have been
retrieved, setting 'dma_addr_next' only if valid data is available.

This solution prevents the use of uninitialized data, maintaining
defined behavior for 'dma_addr_next' in all cases, and aligns with
expected usage of I2S RX descriptor data.

Signed-off-by: Suraj Sonawane <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: SurajSonawane2415

sound/soc/bcm/bcm63xx-pcm-whistler.c

@@ -256,12 +256,16 @@ static irqreturn_t i2s_dma_isr(int irq, void *bcm_i2s_priv)
 
 		offlevel = (int_status & I2S_RX_DESC_OFF_LEVEL_MASK) >>
 			   I2S_RX_DESC_OFF_LEVEL_SHIFT;
+		bool val_read = false;
 		while (offlevel) {
 			regmap_read(regmap_i2s, I2S_RX_DESC_OFF_ADDR, &val_1);
 			regmap_read(regmap_i2s, I2S_RX_DESC_OFF_LEN, &val_2);
+			val_read = true;
 			offlevel--;
 		}
-		prtd->dma_addr_next = val_1 + val_2;
+		if (val_read)
+			prtd->dma_addr_next = val_1 + val_2;
+
 		ifflevel = (int_status & I2S_RX_DESC_IFF_LEVEL_MASK) >>
 			   I2S_RX_DESC_IFF_LEVEL_SHIFT;