netdev - Re: what's in a bus

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Date:	Fri, 4 Nov 2011 23:02:06 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Rick Jones <rick.jones2@...com>
CC:	<netdev@...r.kernel.org>, <rusty@...tcorp.com.au>, <mst@...hat.com>
Subject: Re: what's in a bus_info

On Fri, 2011-11-04 at 15:27 -0700, Rick Jones wrote:
> ...or would an interface name smell as sweet? (as PCI bus addressing)
> 
> Is there a "standard" for what is returned in bus_info of 
> ethtool_drvinfo?  I have been very used to seeing PCI bus addressing 
> information in that field (at least as displayed by ethtool -i) and when 
> I went to "leverage how to" from other drivers, to add "native" ethtool 
> -i support to virtio_net, I ended-up with "eth0" rather than the PCI 
> information I see in lspci output and in ethtool -i against other 
> devices.  Including an emulated e1000 interface in the same kernel.
>
> What I'm doing is calling pci_name(), feeding it with to_pci_dev() from 
> the address of the struct device in the struct net_device.

to_pci_dev() just uses container_of() to find a pci_dev when you have a
pointer to the generic device structure embedded in it.  However, you're
passing a pointer to the device embedded in a net_device.  The net
device is a child of the PCI device, so you need to do:

	dev_dev = dev->dev.parent;

And you don't even have to assume that the parent is a PCI device,
because you can use the generic dev_name().

But you don't even need to this, since the ethtool core has a default
implementation that does this...

[...]
> BTW, I notice some drivers call strlcpy and some strncpy, and some even 
> call strcpy.  Is there one that is meant to be preferred over the others?

strlcpy() is preferred - if it has to truncate, it will at least leave a
null terminator, as clients may expect.  Back when drivers handled
SIOCETHTOOL directly strncpy() may have been preferable since they were
responsible for initialising the entire structure returned to
user-space.

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.

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