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Thu, 03 Sep 2026 12:31:12 -0700 (PDT) From: Zhian Liang To: Dmitry Torokhov Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Zhian Liang Subject: [PATCH 2/2] Input: tca8418_keypad - fix race condition in interrupt handler Date: Fri, 4 Sep 2026 03:29:42 +0800 Message-Id: <20260903192942.21906-2-liangzhan5dev@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260903192942.21906-1-liangzhan5dev@gmail.com> References: <20260903192942.21906-1-liangzhan5dev@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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, ®); 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, ®); + 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