Re: [PATCH 2/2] usbip: block SET_INTERFACE for isoc alt settings

[Sascha Grunert]

On Wed, Jul 01, 2026, Greg Kroah-Hartman wrote:
> What commit id does this fix?

The limitation goes back to the original import:

Fixes: 4d7b5c7f8ad4 ("Staging: USB/IP: add host driver")

tweak_set_interface_cmd() has always forwarded SET_INTERFACE
unconditionally, which is fine until an alt setting with isochronous
endpoints is activated.

> Why is this not an error? And if a user sees this, what can they do
> about it?
>
> > + return 0;
>
> Why isn't this an error?

Returning 0 here means "handled" in tweak_special_requests() semantics
(!err = 1 = tweaked), so the URB is completed with success and never
submitted to the HCD. If we returned an error instead,
tweak_special_requests() would return 0 (not tweaked) and the URB
goes through to the hardware, the isoc alt setting activates, the
transfers fail, and the device disconnects, which is the problem
this patch is trying to prevent.

You're right that the user can't act on the log message though. I'll
change dev_info to dev_dbg in v2.

Thanks,
Sascha