media: et8ek8: Decrease stack usage

The et8ek8 driver combines I²C register writes to a single array that it
passes to i2c_transfer(). The maximum number of writes is 48 at once,
decrease it to 8 and make more transfers if needed.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/i2c/et8ek8/et8ek8_driver.c

@@ -43,7 +43,7 @@
 
 #define ET8EK8_NAME		"et8ek8"
 #define ET8EK8_PRIV_MEM_SIZE	128
-#define ET8EK8_MAX_MSG		48
+#define ET8EK8_MAX_MSG		8
 
 struct et8ek8_sensor {
 	struct v4l2_subdev subdev;
@@ -220,7 +220,8 @@ static void et8ek8_i2c_create_msg(struct i2c_client *client, u16 len, u16 reg,
 
 /*
  * A buffered write method that puts the wanted register write
- * commands in a message list and passes the list to the i2c framework
+ * commands in smaller number of message lists and passes the lists to
+ * the i2c framework
  */
 static int et8ek8_i2c_buffered_write_regs(struct i2c_client *client,
 					  const struct et8ek8_reg *wnext,
@@ -231,11 +232,7 @@ static int et8ek8_i2c_buffered_write_regs(struct i2c_client *client,
 	int wcnt = 0;
 	u16 reg, data_length;
 	u32 val;
-
-	if (WARN_ONCE(cnt > ET8EK8_MAX_MSG,
-		      ET8EK8_NAME ": %s: too many messages.\n", __func__)) {
-		return -EINVAL;
-	}
+	int rval;
 
 	/* Create new write messages for all writes */
 	while (wcnt < cnt) {
@@ -249,10 +246,21 @@ static int et8ek8_i2c_buffered_write_regs(struct i2c_client *client,
 
 		/* Update write count */
 		wcnt++;
+
+		if (wcnt < ET8EK8_MAX_MSG)
+			continue;
+
+		rval = i2c_transfer(client->adapter, msg, wcnt);
+		if (rval < 0)
+			return rval;
+
+		cnt -= wcnt;
+		wcnt = 0;
 	}
 
-	/* Now we send everything ... */
-	return i2c_transfer(client->adapter, msg, wcnt);
+	rval = i2c_transfer(client->adapter, msg, wcnt);
+
+	return rval < 0 ? rval : 0;
 }
 
 /*