From c3d6362b8717759de7f2086f9665a4d96cacbc51 Mon Sep 17 00:00:00 2001 From: Alex Murray Date: Thu, 15 Jan 2009 13:51:08 -0800 Subject: [PATCH] hwmon: applesmc: fix light sensor readings on newer MacBooks The light sensors ALV0 and ALV1 on newer MacBooks (early 2008 and later) changed to report 10 bytes instead the earlier 6, and the sensor encoding subsequently changed. As a result, the reported light sensors readings are much too low. Via experiments leading up to this patch, it seems only the ALV0 is reporting data, and the most useful value therein is a 10-bit big-endian value at offset 6. This suggests that a new protocol was added as a backward-compatible replacement on top of the old one. This patch makes applesmc report the improved light sensor reading for the new machines, on a scale in conformance with earlier ones. Signed-off-by: Alex Murray Signed-off-by: Henrik Rydberg Cc: Nicolas Boichat Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/hwmon/applesmc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c index dca47a591ba..e3018623658 100644 --- a/drivers/hwmon/applesmc.c +++ b/drivers/hwmon/applesmc.c @@ -590,6 +590,11 @@ static ssize_t applesmc_light_show(struct device *dev, } ret = applesmc_read_key(LIGHT_SENSOR_LEFT_KEY, buffer, data_length); + /* newer macbooks report a single 10-bit bigendian value */ + if (data_length == 10) { + left = be16_to_cpu(*(__be16 *)(buffer + 6)) >> 2; + goto out; + } left = buffer[2]; if (ret) goto out; -- 2.41.1