media: platform: vivid-cec: use 64-bit arithmetic instead of 32-bit

Add suffix ULL to constant 10 in order to give the compiler complete
information about the proper arithmetic to use. Notice that this
constant is used in a context that expects an expression of type
u64 (64 bits, unsigned).

The expression len * 10 * CEC_TIM_DATA_BIT_TOTAL is currently being
evaluated using 32-bit arithmetic.

Also, remove unnecessary parentheses and add a code comment to make it
clear what is the reason of the code change.

Addresses-Coverity-ID: 1454996 ("Unintentional integer overflow")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/vivid/vivid-cec.c

@@ -70,8 +70,15 @@ static void vivid_cec_pin_adap_events(struct cec_adapter *adap, ktime_t ts,
 
 	if (adap == NULL)
 		return;
-	ts = ktime_sub_us(ts, (CEC_TIM_START_BIT_TOTAL +
-			       len * 10 * CEC_TIM_DATA_BIT_TOTAL));
+
+	/*
+	 * Suffix ULL on constant 10 makes the expression
+	 * CEC_TIM_START_BIT_TOTAL + 10ULL * len * CEC_TIM_DATA_BIT_TOTAL
+	 * to be evaluated using 64-bit unsigned arithmetic (u64), which
+	 * is what ktime_sub_us expects as second argument.
+	 */
+	ts = ktime_sub_us(ts, CEC_TIM_START_BIT_TOTAL +
+			       10ULL * len * CEC_TIM_DATA_BIT_TOTAL);
 	cec_queue_pin_cec_event(adap, false, ts);
 	ts = ktime_add_us(ts, CEC_TIM_START_BIT_LOW);
 	cec_queue_pin_cec_event(adap, true, ts);