[PATCH 1/2] Input: tca8418_keypad - Add devm cleanup to disable interrupts on unload

[PATCH 1/2] Input: tca8418_keypad - Add devm cleanup to disable interrupts on unload

[Zhian Liang]

tca8418_configure() enables TCA8418 interrupts by writing the CFG
register.  If input_register_device() fails afterwards, probe returns
an error and devres releases the IRQ handler, but the hardware is
left with interrupts still enabled.

Fix it by registering a devm action that clears the CFG register
 when the device is released, disabling
all interrupts on both probe failure and driver unbind.

Signed-off-by: Zhian Liang <liangzhan5dev@gmail.com>
---
 drivers/input/keyboard/tca8418_keypad.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/input/keyboard/tca8418_keypad.c b/drivers/input/keyboard/tca8418_keypad.c
index 36d4a7c38bb1..9f0aace6bd21 100644
--- a/drivers/input/keyboard/tca8418_keypad.c
+++ b/drivers/input/keyboard/tca8418_keypad.c
@@ -270,6 +270,20 @@ static int tca8418_configure(struct tca8418_keypad *keypad_data,
 	return error;
 }
 
+static void tca8418_disable_hw(void *data)
+{
+	struct tca8418_keypad *keypad_data = data;
+	int error;
+
+	error = tca84818_write_byte(keypad_data, REG_CFG, 0);
+	if (error)
+		dev_warn(&keypad_data->client->dev, "unable to disable interrupts: %d\n", error);
+
+	error = tca8418_write_byte(keypad_data, REG_INT_STAT, 0xff);
+	if (error)
+		dev_warn(&keypad_data->client->dev, "unable to clear interrupt status: %d\n", error);
+}
+
 static int tca8418_keypad_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
@@ -356,6 +370,10 @@ static int tca8418_keypad_probe(struct i2c_client *client)
 	if (error < 0)
 		return error;
 
+	error = devm_add_action_or_reset(dev, tca8418_diable_hw, keypad_data);
+	if (error)
+		return error;
+
 	error = input_register_device(input);
 	if (error) {
 		dev_err(dev, "Unable to register input device, error: %d\n",
-- 
2.34.1

[PATCH 2/2] Input: tca8418_keypad - fix race condition in interrupt handler

[Zhian Liang]

There is a race condition in tca8418_irq_handler() where a new key event
can be lost if it arrives after the FIFO is drained but before the
interrupt status register is cleared.

Fix this by re-reading INT_STAT after draining the FIFO and repeating
the process if K_INT is still asserted. This ensures the FIFO is truly
empty before clearing interrupts.

The FIFO depth is 10 events, so a loop limit of 16 provides sufficient
margin while preventing infinite loops in case of hardware misbehavior.

Signed-off-by: Zhian Liang <liangzhan5dev@gmail.com>
---
 drivers/input/keyboard/tca8418_keypad.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/input/keyboard/tca8418_keypad.c b/drivers/input/keyboard/tca8418_keypad.c
index 9f0aace6bd21..0952370c0636 100644
--- a/drivers/input/keyboard/tca8418_keypad.c
+++ b/drivers/input/keyboard/tca8418_keypad.c
@@ -212,6 +212,7 @@ static irqreturn_t tca8418_irq_handler(int irq, void *dev_id)
 	struct tca8418_keypad *keypad_data = dev_id;
 	u8 reg;
 	int error;
+	int max_loops = 16;
 
 	error = tca8418_read_byte(keypad_data, REG_INT_STAT, &reg);
 	if (error) {
@@ -225,9 +226,19 @@ static irqreturn_t tca8418_irq_handler(int irq, void *dev_id)
 
 	if (reg & INT_STAT_OVR_FLOW_INT)
 		dev_warn(&keypad_data->client->dev, "overflow occurred\n");
+	do {
+		if (reg & INT_STAT_K_INT)
+			tca8418_read_keypad(keypad_data);
+
+		/* Re-read interrupt status to check for new events */
+		error = tca8418_read_byte(keypad_data, REG_INT_STAT, &reg);
+		if (error) {
+			dev_err(&keypad_data->client->dev,
+				"unable to re-read REG_INT_STAT\n");
+			return IRQ_HANDLED;
+		}
 
-	if (reg & INT_STAT_K_INT)
-		tca8418_read_keypad(keypad_data);
+	} while ((reg & INT_STAT_K_INT) && --max_loops);
 
 	/* Clear all interrupts, even IRQs we didn't check (GPI, CAD, LCK) */
 	reg = 0xff;
-- 
2.34.1

[PATCH v2] Input: tca8418_keypad - Add devm cleanup to disable interrupts on unload

[Zhian Liang]

tca8418_configure() enables TCA8418 interrupts by writing the CFG
register.  If input_register_device() fails afterwards, probe returns
an error and devres releases the IRQ handler, but the hardware is
left with interrupts still enabled.

Fix it by registering a devm action that clears the CFG register
 when the device is released, disabling
all interrupts on both probe failure and driver unbind.

Signed-off-by: Zhian Liang <liangzhan5dev@gmail.com>

---
Changes in v2:
- Fixed typo: tca84818_write_byte -> tca8418_write_byte
- Fixed typo: tca8418_diable_hw -> tca8418_disable_hw
---
 drivers/input/keyboard/tca8418_keypad.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/input/keyboard/tca8418_keypad.c b/drivers/input/keyboard/tca8418_keypad.c
index 36d4a7c38bb1..413b404a08ba 100644
--- a/drivers/input/keyboard/tca8418_keypad.c
+++ b/drivers/input/keyboard/tca8418_keypad.c
@@ -270,6 +270,20 @@ static int tca8418_configure(struct tca8418_keypad *keypad_data,
 	return error;
 }
 
+static void tca8418_disable_hw(void *data)
+{
+	struct tca8418_keypad *keypad_data = data;
+	int error;
+
+	error = tca8418_write_byte(keypad_data, REG_CFG, 0);
+	if (error)
+		dev_warn(&keypad_data->client->dev, "unable to disable interrupts: %d\n", error);
+
+	error = tca8418_write_byte(keypad_data, REG_INT_STAT, 0xff);
+	if (error)
+		dev_warn(&keypad_data->client->dev, "unable to clear interrupt status: %d\n", error);
+}
+
 static int tca8418_keypad_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
@@ -356,6 +370,10 @@ static int tca8418_keypad_probe(struct i2c_client *client)
 	if (error < 0)
 		return error;
 
+	error = devm_add_action_or_reset(dev, tca8418_disable_hw, keypad_data);
+	if (error)
+		return error;
+
 	error = input_register_device(input);
 	if (error) {
 		dev_err(dev, "Unable to register input device, error: %d\n",
-- 
2.34.1

Re: [PATCH 1/2] Input: tca8418_keypad - Add devm cleanup to disable interrupts on unload

[Dmitry Torokhov]

Hi Zhian,

On Fri, Sep 04, 2026 at 03:29:41AM +0800, Zhian Liang wrote:
> tca8418_configure() enables TCA8418 interrupts by writing the CFG
> register.  If input_register_device() fails afterwards, probe returns
> an error and devres releases the IRQ handler, but the hardware is
> left with interrupts still enabled.

What kind of issues does it cause?

Thanks.

-- 
Dmitry