[PATCH net] net: dsa: mv88e6xxx: Fix switchdev error code

[PATCH net] net: dsa: mv88e6xxx: Fix switchdev error code

[Elliot Ayrey]

Calling a switchdev notifier encodes additional information into the
return code. Using this value directly makes error messages confusing.

Use notifer_to_errno() to restore the original errno value.

Fixes: 830763b96720 ("net: dsa: mv88e6xxx: mac-auth/MAB implementation")
Signed-off-by: Elliot Ayrey <elliot.ayrey@alliedtelesis.co.nz>
---
 drivers/net/dsa/mv88e6xxx/switchdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/dsa/mv88e6xxx/switchdev.c b/drivers/net/dsa/mv88e6xxx/switchdev.c
index 4c346a884fb2..7c59eca0270d 100644
--- a/drivers/net/dsa/mv88e6xxx/switchdev.c
+++ b/drivers/net/dsa/mv88e6xxx/switchdev.c
@@ -79,5 +79,5 @@ int mv88e6xxx_handle_miss_violation(struct mv88e6xxx_chip *chip, int port,
 				       brport, &info.info, NULL);
 	rtnl_unlock();
 
-	return err;
+	return notifier_to_errno(err);
 }

Re: [PATCH net] net: dsa: mv88e6xxx: Fix switchdev error code

[Andrew Lunn]

On Tue, Dec 17, 2024 at 05:39:30PM +1300, Elliot Ayrey wrote:
> Calling a switchdev notifier encodes additional information into the
> return code. Using this value directly makes error messages confusing.
> 
> Use notifer_to_errno() to restore the original errno value.
> 
> Fixes: 830763b96720 ("net: dsa: mv88e6xxx: mac-auth/MAB implementation")
> Signed-off-by: Elliot Ayrey <elliot.ayrey@alliedtelesis.co.nz>
> ---
>  drivers/net/dsa/mv88e6xxx/switchdev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx/switchdev.c b/drivers/net/dsa/mv88e6xxx/switchdev.c
> index 4c346a884fb2..7c59eca0270d 100644
> --- a/drivers/net/dsa/mv88e6xxx/switchdev.c
> +++ b/drivers/net/dsa/mv88e6xxx/switchdev.c
> @@ -79,5 +79,5 @@ int mv88e6xxx_handle_miss_violation(struct mv88e6xxx_chip *chip, int port,
>  				       brport, &info.info, NULL);
>  	rtnl_unlock();
>  
> -	return err;
> +	return notifier_to_errno(err);

I just had a quick look at other users of call_switchdev_notifiers()
and all but vxlan_core.c and this one discarded the return
value. Would that be a better fix, making the code more uniform?

	Andrew

Re: [PATCH net] net: dsa: mv88e6xxx: Fix switchdev error code

[Elliot Ayrey]

On Tue, 2024-12-17 at 10:54 +0100, Andrew Lunn wrote:
> I just had a quick look at other users of call_switchdev_notifiers()
> and all but vxlan_core.c and this one discarded the return
> value. Would that be a better fix, making the code more uniform?
> 
> 	Andrew

Hi Andrew, I am hesitant to remove this error as it was very helpful
during development and helped to diagnose some subtle issues that would
have otherwise been very hard to notice.

Re: [PATCH net] net: dsa: mv88e6xxx: Fix switchdev error code

[Vladimir Oltean]

On Sun, Jan 26, 2025 at 10:07:26PM +0000, Elliot Ayrey wrote:
> On Tue, 2024-12-17 at 10:54 +0100, Andrew Lunn wrote:
> > I just had a quick look at other users of call_switchdev_notifiers()
> > and all but vxlan_core.c and this one discarded the return
> > value. Would that be a better fix, making the code more uniform?
> > 
> > 	Andrew
> 
> Hi Andrew, I am hesitant to remove this error as it was very helpful
> during development and helped to diagnose some subtle issues that would
> have otherwise been very hard to notice.

Can you give more details about how you encountered this issue?
One could similarly argue that a call_switchdev_notifiers() error was
ignored until now, and maybe the system still did something reasonable
and thus, properly handling the error now risks introducing a regression
for them. No way to really know except if the commit author (you) makes
a reasonable analysis in the commit message leading to the conclusion
that the patch is worthy of backporting to stable kernels (i.e. fixes a
user-visible incorrect behavior).