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authorHenrique de Moraes Holschuh <hmh@hmh.eng.br>2009-04-04 04:25:49 +0000
committerLen Brown <len.brown@intel.com>2009-04-04 03:14:52 -0400
commita4d5effcc73749ee3ebbf578d162905e6fa4e07d (patch)
tree1160b3763004be227cfe3d6c15e4235a9ccf69b7 /Documentation/laptops
parent2586d5663d0a17d69383acf6110f16a979a07c4e (diff)
downloadlinux-next-a4d5effcc73749ee3ebbf578d162905e6fa4e07d.tar.gz
thinkpad-acpi: restrict access to some firmware LEDs
Some of the ThinkPad LEDs indicate critical conditions that can cause data loss or cause hardware damage when ignored (e.g. force-ejecting a powered up bay; ignoring a failing battery, or empty battery; force- undocking with the dock buses still active, etc). On almost all ThinkPads, LED access is write-only, and the firmware usually does fire-and-forget signaling on them, so you effectively lose whatever message the firmware was trying to convey to the user when you override the LED state, without any chance to restore it. Restrict access to all LEDs that can convey important alarms, or that could mislead the user into incorrectly operating the hardware. This will make the Lenovo engineers less unhappy about the whole issue. Allow users that really want it to still control all LEDs, it is the unaware user that we have to worry about. Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'Documentation/laptops')
-rw-r--r--Documentation/laptops/thinkpad-acpi.txt11
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index de6f14c79070..bce1d959b703 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -901,6 +901,17 @@ some older ThinkPad models, it is possible to query the status of the
LED indicators as well. Newer ThinkPads cannot query the real status
of the LED indicators.
+Because misuse of the LEDs could induce an unaware user to perform
+dangerous actions (like undocking or ejecting a bay device while the
+buses are still active), or mask an important alarm (such as a nearly
+empty battery, or a broken battery), access to most LEDs is
+restricted.
+
+Unrestricted access to all LEDs requires that thinkpad-acpi be
+compiled with the CONFIG_THINKPAD_ACPI_UNSAFE_LEDS option enabled.
+Distributions must never enable this option. Individual users that
+are aware of the consequences are welcome to enabling it.
+
procfs notes:
The available commands are: