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i2c: complain loudly if __i2c_transfer has no proper callback

Message ID 20240606203657.22286-2-wsa+renesas@sang-engineering.com
State New
Delegated to: Wolfram Sang
Headers show
Series i2c: complain loudly if __i2c_transfer has no proper callback | expand

Commit Message

Wolfram Sang June 6, 2024, 8:36 p.m. UTC
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(-)

Comments

Jean Delvare June 8, 2024, 7:24 a.m. UTC | #1
Hi Wolfram,

On Thu,  6 Jun 2024 22:36:58 +0200, Wolfram Sang wrote:
> 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;

Then you'll have to add a check on I2C_FUNC_I2C (or
adapter->algo->master_xfer, whatever you prefer) before calling
i2c_smbus_xfer_emulated(). Otherwise using i2c-dev on a slave-only
adapter will trigger the WARN_ON_ONCE immediately.
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Patch

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;