RE: [PATCH net-next v2 2/3] rtnetlink: add IFLA_PARENT_[DEV|DEV_BUS]_NAME

From: Loic Poulain <redacted>
Sent: Friday, June 11, 2021 8:37 PM

Hi Parav,

On Fri, 11 Jun 2021 at 15:01, Parav Pandit [off-list ref] wrote:

quoted

quoted

From: Loic Poulain <redacted>
Sent: Thursday, June 10, 2021 11:15 PM

From: Johannes Berg <redacted>

In some cases, for example in the upcoming WWAN framework changes,
there's no natural "parent netdev", so sometimes dummy netdevs are
created or similar. IFLA_PARENT_DEV_NAME is a new attribute intended
to contain a device (sysfs, struct device) name that can be used
instead when creating a new netdev, if the rtnetlink family implements it.

As suggested by Parav Pandit, we also introduce
IFLA_PARENT_DEV_BUS_NAME attribute in order to uniquely identify a
device on the system (with bus/name pair).

ip-link(8) support for the generic parent device attributes will
help us avoid code duplication, so no other link type will require a
custom code to handle the parent name attribute. E.g. the WWAN
interface creation command will looks like this:

$ ip link add wwan0-1 parent-dev wwan0 type wwan channel-id 1

So, some future subsystem (or driver) FOO will have an interface
creation command that looks like this:

$ ip link add foo1-3 parent-dev foo1 type foo bar-id 3 baz-type Y

Below is an example of dumping link info of a random device with
these new
attributes:

$ ip --details link show wlp0s20f3
  4: wlp0s20f3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
noqueue
     state UP mode DORMANT group default qlen 1000
     ...
     parent_devname 0000:00:14.3 parent_busname pci

Showing bus first followed device is more preferred approach to see

hierarchy.

quoted

Please change their sequence.

You should drop "name" suffix.
"parent_bus" and "parent_dev" are just fine.

Do you think it can also be dropped for the IFLA symbol (IFLA_PARENT_DEV
&& IFLA_PARENT_BUS_NAME).

IFLA symbol with _NAME is fine as it covers what the field is.