[PATCH] nfc: pn533: add error handling for i2c_master_send() in pn533_i2c_send_ack()

[Wenyuan Li]

In pn533_i2c_send_ack(), the return value of i2c_master_send() is not
checked. If the I2C transfer fails, the driver continues execution
without detecting the error, which may lead to incorrect device state
or silent failures.

Specifically:
1. The ACK may not be sent to the device, leaving it in an undefined state
2. The caller (pn533_i2c_abort_cmd()) ignores the return value entirely
3. No error logging is provided for debugging

Fix this by:
- Adding proper return value check for i2c_master_send()
- Converting partial sends to -EIO and preserving kernel error codes
- Adding nfc_err() logging with %pe format for human-readable errors
- Propagating the error to the caller pn533_i2c_abort_cmd()

Even if ACK sending fails, the abort procedure continues by scheduling
cmd_complete_work to ensure userspace is notified, but the error is
properly logged for debugging.

Signed-off-by: Wenyuan Li <2063309626@xxxxxx>
---
 drivers/nfc/pn533/i2c.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/nfc/pn533/i2c.c b/drivers/nfc/pn533/i2c.c
index 132c050a365d..4d771fe24f70 100644
--- a/drivers/nfc/pn533/i2c.c
+++ b/drivers/nfc/pn533/i2c.c
@@ -40,8 +40,15 @@ static int pn533_i2c_send_ack(struct pn533 *dev, gfp_t flags)
 	struct i2c_client *client = phy->i2c_dev;
 	static const u8 ack[6] = {0x00, 0x00, 0xff, 0x00, 0xff, 0x00};
 	/* spec 6.2.1.3:  Preamble, SoPC (2), ACK Code (2), Postamble */
+	int ret;
 
-	return i2c_master_send(client, ack, 6);
+	ret = i2c_master_send(client, ack, 6);
+	if (ret != 6) {
+		nfc_err(&client->dev, "failed to send ACK: %pe\n", ERR_PTR(ret));
+		return ret < 0 ? ret : -EIO;
+	}
+
+	return 0;
 }
 
 static int pn533_i2c_send_frame(struct pn533 *dev,
@@ -82,12 +89,14 @@ static int pn533_i2c_send_frame(struct pn533 *dev,
 static void pn533_i2c_abort_cmd(struct pn533 *dev, gfp_t flags)
 {
 	struct pn533_i2c_phy *phy = dev->phy;
+	int ret;
 
 	phy->aborted = true;
 
 	/* An ack will cancel the last issued command */
-	pn533_i2c_send_ack(dev, flags);
-
+	ret = pn533_i2c_send_ack(dev, flags);
+	if (ret)
+		nfc_err(&phy->i2c_dev->dev, "failed to abort command: %pe\n", ERR_PTR(ret));
 	/* schedule cmd_complete_work to finish current command execution */
 	pn533_recv_frame(phy->priv, NULL, -ENOENT);
 }
-- 
2.43.0