[media] saa7164: Improvements for I2C handling

Workaround oddball I2C issues caused by using newer
SILABS devices.
Signed-off-by: NSteven Toth <stoth@kernellabs.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/pci/saa7164/saa7164-api.c

@@ -1385,7 +1385,8 @@ int saa7164_api_i2c_read(struct saa7164_i2c *bus, u8 addr, u32 reglen, u8 *reg,
 	 *       08... register address
 	 */
 	memset(buf, 0, sizeof(buf));
-	memcpy((buf + 2 * sizeof(u32) + 0), reg, reglen);
+	if (reg)
+		memcpy((buf + 2 * sizeof(u32) + 0), reg, reglen);
 	*((u32 *)(buf + 0 * sizeof(u32))) = reglen;
 	*((u32 *)(buf + 1 * sizeof(u32))) = datalen;
 
@@ -1473,6 +1474,14 @@ int saa7164_api_i2c_write(struct saa7164_i2c *bus, u8 addr, u32 datalen,
 	 *       04-07 dest bytes to write
 	 *       08... register address
 	 */
+	if (datalen == 1) {
+		/* Workaround for issues with i2c components
+		 * that issue writes with no data. IE: SI2168/2157
+		 * Increase reglen by 1, strobe out an additional byte,
+		 * ignored by SI2168/2157.
+		 */
+		datalen++;
+	}
 	*((u32 *)(buf + 0 * sizeof(u32))) = reglen;
 	*((u32 *)(buf + 1 * sizeof(u32))) = datalen - reglen;
 	memcpy((buf + 2 * sizeof(u32)), data, datalen);