Re: [PATCH v4] driver core: avoid klist_remove() on unattached knode_driver

In-Reply-To: <[email protected]>
References: <[email protected]>

On Fri, Aug 21, 2026 at 03:54:44AM +0200, Danilo Krummrich wrote:
> usb_driver_claim_interface() is the only callsite in the kernel that
> does set dev->driver without a subsequent device_bind_driver().

Small correction, I think there are a few more. usb_port
(drivers/usb/core/port.c:782) sets dev->driver before device_register(),
and usb_port_driver has no ->match and no ->probe, so it depends entirely
on the __device_attach() dev->driver path to get bound. ccwgroup
(drivers/s390/cio/ccwgroup.c:385) and pata_parport
(drivers/ata/pata_parport/pata_parport.c:515) do the same. So that path
doesn't look USB-claim-specific, and if we ever want to remove it,
usb_port would need a ->match() first.

For the root cause, what about this: in usb_driver_claim_interface(),
when the interface isn't registered yet, just don't set dev->driver --
record the claim on struct usb_interface instead. Then, once the
interface gets added in usb_set_configuration(), bind it explicitly with
device_bind_driver(). That skips ->probe, which is exactly what
usb_audio's claim-now-bind-later needs, and it also attaches
knode_driver so teardown is safe. The __device_attach() path can stay
for w1/ccwgroup/pata_parport.

Does that sound reasonable?