Just want to make sure I understand the history here.

looks like iwconfig is part of net-wireless/wireless-tools

and is presently only part of dev image.

Did it used to be in included in the base image as well?

Agreed disabling the wireless-power module in lmt here:

  https://chromium-review.googlesource.com/c/422094/

is the right short-term solution.

Should the long term plan be to:

1. include iwconfig in base image or
2. patch wireless-power module to use an alternative to iwconfig if available?
3. something else.

iw is what we should be using for this instead of iwconfig.

The patch that enabled use of iw:

We support only nl80211 WiFi devices; no more WEXT support:
- remove old script that used iwconfig
- add new module script that uses iw to ena/dis power save

Note this also fixes wifi power save operation for nl80211 devices as the iwconfig code never worked right due to it checking the wrong file under /sys.  This means we should now have lower latency on AC because we'll turn off power save.

https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/app-laptop/laptop-mode-tools/files/0005-switch-wifi-support-to-nl80211.patch

(I already patched the wireless-power module in upstream, but since our long/mid-term plan is to get rid of laptop-mode altogether it's probably not worth to integrate it)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/8f4e89675d36ff3cd937281cc970933405c0dbc7

commit 8f4e89675d36ff3cd937281cc970933405c0dbc7
Author: Matthias Kaehlcke <mka@chromium.org>
Date: Sat Dec 17 00:53:33 2016

laptop-mode-tools: Disable module wireless-power

Chrome OS uses the 'wifi-nl80211-powermgmt' module to enable/disable
WiFi powersave mode. The original laptop-mode module 'wireless-power'
is still enabled and exits with an error since it can't find iwconfig.
This causes "laptop_mode force" to end prematurely. Disable the module.

BUG= chromium:675286 
TEST=manual with additional logs in laptop_mode script

Change-Id: I30398aff7f0262f5bc5bcbc963e0246434a15228
Reviewed-on: https://chromium-review.googlesource.com/422094
Commit-Ready: Matthias Kaehlcke <mka@chromium.org>
Tested-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>

[rename] https://crrev.com/8f4e89675d36ff3cd937281cc970933405c0dbc7/app-laptop/laptop-mode-tools/laptop-mode-tools-1.59-r39.ebuild
[add] https://crrev.com/8f4e89675d36ff3cd937281cc970933405c0dbc7/app-laptop/laptop-mode-tools/files/0034-wireless-power-disable-module.patch
[modify] https://crrev.com/8f4e89675d36ff3cd937281cc970933405c0dbc7/app-laptop/laptop-mode-tools/laptop-mode-tools-1.59.ebuild

Additional info:

The premature exit of 'laptop_mode force' can have a nasty side-effect. After the command exits often no other laptop-mode instance can acquire the inner LMT lock (fd=9) for 30s:

[   16.389989] MKA: LM (1727): lmt_main_function: force
[   16.517003] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   17.555442] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   18.248635] MKA: wireless-power (1727): EXIT: no iwconfig
[   18.565693] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   19.571777] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   20.576955] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   21.581577] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   22.592947] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   23.603972] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   24.614005] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   25.624140] MKA: LM (1762): Couldn't acquire lock. PARAMS='force modules=wifi-nl80211-powermgmt')
[   26.635638] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   27.646647] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   28.657003] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   29.667449] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   30.677886] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   31.691165] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   32.698771] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   33.707761] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   34.718627] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   35.728898] MKA: LM (1851): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=1-0:1.0')
[   36.741048] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   37.751542] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   38.762595] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   39.772831] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   40.782976] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   41.793451] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   42.800280] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   43.807293] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   44.817916] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   45.824685] MKA: LM (2154): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=usb6')
[   46.834536] MKA: LM (2188): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=6-1')
[   47.847189] MKA: LM (2188): Couldn't acquire lock. PARAMS='force modules=usb-autosuspend devices=6-1')
[   48.255753] MKA: LM (2188): lmt_main_function: force modules=usb-autosuspend devices=6-1

Apparently the 30s period stems from the wait time of the outer lock (fd=8), if it is reduced the inner lock can be acquired earlier. Not sure how the wait time of the outer lock affects the inner lock.

Verified on build 9334.33.0