amd64/181357: LCD Brightness Control not working on Lenovo X121e (ACPI issue?)

[Matthias Petermann]

The following reply was made to PR amd64/181357; it has been noted by GNATS.

From: Matthias Petermann <matthias at petermann-it.de>
To: bug-followup at FreeBSD.org, matthias at petermann-it.de, 
 current at freebsd.org
Cc:  
Subject: Re: amd64/181357: LCD Brightness Control not working on Lenovo X121e
 (ACPI issue?)
Date: Sat, 24 Aug 2013 17:08:25 +0200

 Hello,
 
 regarding this PR I made some further observation. Even the 
 acpi_ec_write seems to not have any effect on the brightness, the values 
 set to the appropriate register (IBM_EC_BRIGHTNESS   0x31) survive a 
 reboot.
 
 Looks like the values are stored correctly, but EC doesn't care for them 
 when setting brightness?
 
 I'm not sure where to look next. Could this be a hardware issue with the 
 Device?
 
 Kind regards,
 Matthias