tree 62fab6f14519a66f26ecc804cc3dab6a5357f533
parent 533990fd3df6d49c6fab6d9243081bda5e9ef1d6
author Brian Norris <briannorris@chromium.org> 1563835426 -0700
committer chrome-bot <chrome-bot@chromium.org> 1564128495 -0700

check_ethernet: promote rescan_usb_hubs to recovery_method

Today, we may run rescan_usb_hubs a number of times just because it's
part of the find_ethernet_interfaces() function. This isn't really a
good idea for cases that aren't recoverable -- it wastes a bunch of time
and caues confusing "bouncy" behavior. We can improve this by sharing
the 'recovery_method' logic, which
(a) tries the recovery action
(b) checks whether that action did anything useful
(c) if so, retry connectivity diagnostics; if not, try the next method
    immediately.

This pattern matches what we want for rescan_usb_hubs anyway: just try
it once, if there were no operational links; don't re-try it several
times as an implicit part of looking for devices.

This eliminates any logic in find_ethernet_devices(), so we just alias
with search_devices().

A few additions to rescan_usb_hubs() along the way:
 * re-check whether there are any devices (search_devices()) after
   running, to determine our "success"; poll over 15 seconds -- in
   addition to kernel hub enumeration, it can take some time for
   usb_guard to authorize the device
 * factor out some delays until after we iterate over all hubs
 * add a sanity check in case the "${usbhub}/... globbing doesn't match
   anything

BUG=chromium:982940
TEST=manually-induced failures (e.g., delete interface), see how script
     responds

Change-Id: I118db269002ebba9267446bfbbdba7b3bf6e938e
Reviewed-on: https://chromium-review.googlesource.com/1714129
Tested-by: Brian Norris <briannorris@chromium.org>
Commit-Ready: Brian Norris <briannorris@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>