In get_key_adaptec(), a command byte (0x00) is sent to the IR chip via
i2c_master_send() to initiate a key read. However, the return value of
i2c_master_send() is not checked.

If this I2C transfer fails, the IR chip may not receive the read
command, causing the subsequent i2c_master_recv() to read stale or
invalid data. The driver would then return 0 (no key) without logging
the error, making debugging difficult.

Fix this by:
- Checking the return value of i2c_master_send()
- Converting partial sends to -EIO while preserving kernel error codes
- Adding dev_err_ratelimited() logging with %pe format
- Adding similar error logging for the i2c_master_recv() path

If the send fails, return 0 to maintain the existing behavior (no key
detected), but log the error for debugging purposes.

Fixes: e1e2c5756563 ("[media] ivtv: Add Adaptec Remote Controller")
Cc: stable@vger.kernel.org
Signed-off-by: Wenyuan Li <2063309626@qq.com>

---
v2:
- Add error handling for i2c_master_send() as suggested
- Extend checking to i2c_master_recv()
- Use dev_err_ratelimited() instead of dev_err()
- Clarify error handling behavior
- Drop incorrect Fixes tag

v3:
-Add correct Fixes tag
---
 drivers/media/pci/ivtv/ivtv-i2c.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/media/pci/ivtv/ivtv-i2c.c b/drivers/media/pci/ivtv/ivtv-i2c.c
index 28cb22d6a892..c011f2246add 100644
--- a/drivers/media/pci/ivtv/ivtv-i2c.c
+++ b/drivers/media/pci/ivtv/ivtv-i2c.c
@@ -138,11 +138,28 @@ static int get_key_adaptec(struct IR_i2c *ir, enum rc_proto *protocol,
 			   u32 *scancode, u8 *toggle)
 {
 	unsigned char keybuf[4];
+	int ret;
 
 	keybuf[0] = 0x00;
-	i2c_master_send(ir->c, keybuf, 1);
+
+	ret = i2c_master_send(ir->c, keybuf, 1);
+	if (ret != 1) {
+		int err = ret < 0 ? ret : -EIO;
+
+		dev_err_ratelimited(&ir->c->dev, "i2c_master_send failed: %pe\n", ERR_PTR(err));
+
+		/* Preserve existing behavior: treat error as no key */
+		return 0;
+	}
+
 	/* poll IR chip */
-	if (i2c_master_recv(ir->c, keybuf, sizeof(keybuf)) != sizeof(keybuf)) {
+	ret = i2c_master_recv(ir->c, keybuf, sizeof(keybuf));
+	if (ret != sizeof(keybuf)) {
+		int err = ret < 0 ? ret : -EIO;
+
+		dev_err_ratelimited(&ir->c->dev, "i2c_master_recv failed: %pe\n", ERR_PTR(err));
+
+		/* Preserve existing behavior */
 		return 0;
 	}
 
-- 
2.43.0