network device getting opened

Hi all,

I am trying to test the ethernet driver through mounting file system.
A bit strange but the thing is that the ramdisk is not yet up and I
wanted to check
the xmit functionality through the ARP message that kernel sends while
mounting the nfs.
For that, I wanted to know when exactly does the kenel calls the device
open function in net_device structure? Also when exactly does the
dev->xmit will get called. If any one can give code level references,
it will be great.

Regards,
Sagar

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