Allow the lid to be ignored using the use_lid pref

Allow the lid to be ignored using the use_lid pref

In the case where some devices have an optional lid,
the presence of the SW_LID in one of the input events
will cause powerm to treat that as a valid input and
suspend or shutdown the system appropriately.

Howevever, if the system doesn't physically have a lid
but has one logically, we want the power manager
to ignore inputs from that event based on a preference.
This is done at powerm initialization, and is not
dynamically changed.

This change requires this changelist :
http://codereview.chromium.org/6712051/

Change-Id: I16dba1389078a6dd367770db334f0aa8f4e20ec1
Signed-off-by: Benson Leung <bleung@chromium.org>;
Signed-off-by: Todd Broch <tbroch@chromium.org>;

BUG=chromium-os:13260
TEST=
echo 0 > /var/lib/power_manager/use_lid
sudo restart powerm
Close the lid. Ensure that the lid is ignored.
Watch /var/log/power_manager/powerm.LATEST for "Ignoring Lid."
Boot a system without a lid.
Ensure the system doesn't shut down or suspend.

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=94e93d5

[Benson Leung, 2011-03-19 07:05:59]

This CL will create a use_lid config for powerm that will support systems with a
lid input event, but not a physical lid.

This will allow custom builds that echo 0 > /var/lib/power_manager/use_lid in
order to disable the lid function, so the lidless system won't just immediately
suspend or shut down.

[Benson Leung, 2011-03-21 22:13:33]

Add tbroch to reviewers. ptal.

[tbroch1, 2011-03-22 20:06:48]

LGTM
On 2011/03/21 22:13:33, Benson Leung wrote:
> Add tbroch to reviewers. ptal.