Check the two files to ensure the present of Ethernet device and fix bug

For USB ethernet device, it failed by directory existed but the two files (device and vendor) not exited. So now check the two files to ensure the present of Ethernet device.

Also fix a bug that not output of lspci/lsusb was considered as device exists.

BUG=3578

[petkov, 2010-05-26 17:48:33]

This CL seems like an overkill. I believe the goal is not to qualify a device
with a USB-based ethernet adapter (or to qualify the adapter itself). The goal
is not to fail the test when there's such an adapter.

I believe you just need to check for the presence of the two files (device and
vendor) rather than just for the directory, and signal "Not Present" if they're
not there. You don't need any of the other logic.

[Nick Sanders, 2010-05-26 21:20:38]

It may be the case that we'll see non-pcie network cards on other devices, such
as onboard usb enet similar to the way bluetooth or 3g work sometimes. It may be
worthwhile to just enumerate all devices rather than look for specific
components, it's not guaranteed that any particular type of device will be
attached to any particular interface.

On 2010/05/26 17:48:33, petkov wrote:
> This CL seems like an overkill. I believe the goal is not to qualify a device
> with a USB-based ethernet adapter (or to qualify the adapter itself). The goal
> is not to fail the test when there's such an adapter.
> 
> I believe you just need to check for the presence of the two files (device and
> vendor) rather than just for the directory, and signal "Not Present" if
they're
> not there. You don't need any of the other logic.

[Tom Wai-Hong Tam, 2010-05-27 03:33:10]

I agreed that the current approved Ethernet devices only use PCI interface, so
it is enough to check for the presence of the two files. I will remove the other
logic. Once the devices used USB interface become our approved list, we can add
this logic back and make them more generic (wifi and 3G may also do the same
thing).

[Nick Sanders, 2010-05-27 04:02:15]

sgtm

On Wed, May 26, 2010 at 8:33 PM, <waihong@chromium.org> wrote:

> I agreed that the current approved Ethernet devices only use PCI interface,
> so
> it is enough to check for the presence of the two files. I will remove the
> other
> logic. Once the devices used USB interface become our approved list, we can
> add
> this logic back and make them more generic (wifi and 3G may also do the
> same
> thing).
>
>
> http://codereview.chromium.org/2279001/show
>

[petkov, 2010-05-27 04:28:28]

LGTM too
Let's cross the other bridge when we get there...