[PATCH] i2c: complain loudly if __i2c_transfer has no proper callback

[Wolfram Sang <wsa+renesas@sang-engineering.com>]

In a discussion we concluded that having no working callback in
__i2c_transfer is a serious bug, so dev_dbg() is not enough. Turn it
into a WARN.

Link: https://lore.kernel.org/r/20240604171113.232628f9@endymion.delvare
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 drivers/i2c/i2c-core-base.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index db0d1ac82910..e5fd899c28c3 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -2207,10 +2207,8 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 	unsigned long orig_jiffies;
 	int ret, try;
 
-	if (!adap->algo->master_xfer) {
-		dev_dbg(&adap->dev, "I2C level transfers not supported\n");
+	if (WARN_ON_ONCE(!adap->algo->master_xfer))
 		return -EOPNOTSUPP;
-	}
 
 	if (WARN_ON(!msgs || num < 1))
 		return -EINVAL;
-- 
2.43.0