[PATCH v2] gpio: stmpe: Check return value of stmpe_reg_read in stmpe_gpio_irq_sync_unlock

[Wentao Liang <vulab@iscas.ac.cn>]

The stmpe_reg_read function can fail, but its return value is not checked
in stmpe_gpio_irq_sync_unlock. This can lead to silent failures and
incorrect behavior if the hardware access fails.

This patch adds checks for the return value of stmpe_reg_read. If the
function fails, an error message is logged and the function returns
early to avoid further issues.

Fixes: b888fb6f2a27 ("gpio: stmpe: i2c transfer are forbiden in atomic context")
Cc: stable@vger.kernel.org # 4.16+
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
---
 drivers/gpio/gpio-stmpe.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpio-stmpe.c b/drivers/gpio/gpio-stmpe.c
index 75a3633ceddb..222279a9d82b 100644
--- a/drivers/gpio/gpio-stmpe.c
+++ b/drivers/gpio/gpio-stmpe.c
@@ -191,7 +191,7 @@ static void stmpe_gpio_irq_sync_unlock(struct irq_data *d)
 		[REG_IE][CSB] = STMPE_IDX_IEGPIOR_CSB,
 		[REG_IE][MSB] = STMPE_IDX_IEGPIOR_MSB,
 	};
-	int i, j;
+	int ret, i, j;
 
 	/*
 	 * STMPE1600: to be able to get IRQ from pins,
@@ -199,8 +199,16 @@ static void stmpe_gpio_irq_sync_unlock(struct irq_data *d)
 	 * GPSR or GPCR registers
 	 */
 	if (stmpe->partnum == STMPE1600) {
-		stmpe_reg_read(stmpe, stmpe->regs[STMPE_IDX_GPMR_LSB]);
-		stmpe_reg_read(stmpe, stmpe->regs[STMPE_IDX_GPMR_CSB]);
+		ret = stmpe_reg_read(stmpe, stmpe->regs[STMPE_IDX_GPMR_LSB]);
+		if (ret < 0) {
+			dev_err(stmpe->dev, "Failed to read GPMR_LSB: %d\n", ret);
+			goto err;
+		}
+		ret = stmpe_reg_read(stmpe, stmpe->regs[STMPE_IDX_GPMR_CSB]);
+		if (ret < 0) {
+			dev_err(stmpe->dev, "Failed to read GPMR_CSB: %d\n", ret);
+			goto err;
+		}
 	}
 
 	for (i = 0; i < CACHE_NR_REGS; i++) {
@@ -222,6 +230,7 @@ static void stmpe_gpio_irq_sync_unlock(struct irq_data *d)
 		}
 	}
 
+err:
 	mutex_unlock(&stmpe_gpio->irq_lock);
 }
 
-- 
2.42.0.windows.2