On Tue, 2012-07-03 at 15:47 +0000, Arvid Brodin wrote:

(Added MACB "patch" contact Nicolas Ferre to CC list.)

On 2012-06-29 17:24, Ben Hutchings wrote:

quoted

On Fri, 2012-06-29 at 02:36 +0000, Arvid Brodin wrote:

quoted

Hi,

After 'ip link set eth0 up' on an avr32 board (network driver macb), the device ends up in
operational mode "UNKNOWN":

# ip link
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
    link/ether 00:24:74:00:17:9d brd ff:ff:ff:ff:ff:ff

Unplugging and plugging in the network cable gets the device to mode "UP".

This is a problem for me because I'm trying to use this device as a "slave" device (for a
virtual HSR device*) and I need to be able to decide if the slave device is operational or
not.

Following Stephen's advice here:
http://kerneltrap.org/mailarchive/linux-netdev/2008/9/24/3398834 I checked the macb.c code
and noticed they do not call netif_carrier_off() neither before register_netdev() nor in
dev_open().

It should be called after register_netdev() and before the driver's
ndo_open implementation returns.

I'm guessing this allows linkwatch to do netif_carrier_on() some time after the dev_open()?

No, the driver is always responsible for calling
netif_carrier_{on,off}() in a timely manner.  link_watch takes care of
stopping the software TX queues if the link goes down.

Besides not calling netif_carrier_off() in dev_open(), the Cadence/MACB driver calls
netif_carrier_off() in dev_close(). Is this correct?

Unnecessary but harmless.

How should I handle carrier state for a virtual device? The device should have "carrier"
as long as at least one of the underlying physical interfaces is operational (which I
guess means operational state UP). Would it be correct to watch NETDEV_CHANGE and DOWN/UP
events of the slaves and call netif_carrier_on()/off() on the virtual device depending on
the slaves' states?

[...]

That sounds about right.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.