platform/chrome: Expose Chrome OS Lightbar to users
This adds some sysfs entries to provide userspace control of the four-element LED "lightbar" on the Chromebook Pixel. This only instantiates the lightbar controls if the device actually exists. To prevent DoS attacks, this interface is limited to 20 accesses/second, although that rate can be adjusted by a privileged user. On Chromebooks without a lightbar, this should have no effect. On the Chromebook Pixel, you should be able to do things like this: $ cd /sys/devices/virtual/chromeos/cros_ec/lightbar $ echo 0x80 > brightness $ echo 255 > brightness $ $ cat sequence S0 $ echo konami > sequence $ cat sequence KONAMI $ $ cat sequence S0 And $ cd /sys/devices/virtual/chromeos/cros_ec/lightbar $ echo stop > sequence $ echo "4 255 255 255" > led_rgb $ echo "0 255 0 0 1 0 255 0 2 0 0 255 3 255 255 0" > led_rgb $ echo run > sequence Test the DoS prevention with this: $ cd /sys/devices/virtual/chromeos/cros_ec/lightbar $ echo 500 > interval_msec $ time (cat version version version version version version version) Signed-off-by:Bill Richardson <wfrichar@chromium.org> Reviewed-by:
Olof Johansson <olofj@chromium.org> Tested-by:
Doug Anderson <dianders@chromium.org> Reviewed-by:
Benson Leung <bleung@chromium.org> Signed-off-by:
Javier Martinez Canillas <javier.martinez@collabora.co.uk> Tested-by:
Gwendal Grignou <gwendal@chromium.org> Reviewed-by:
Gwendal Grignou <gwendal@chromium.org> Signed-off-by:
Olof Johansson <olof@lixom.net>
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71af4b52
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