Hi, I recently updated the BIOS on my HP Pavilion dv2125nr laptop to F.34 (to enable the virtualization instructions). Since I did this, the Fn keys to control brightness have failed to work properly under Linux, though they work fine before booting (ie. at Grub). Hitting the Fn keys caused the brightness to change to the minimum possible. In fact, /proc/acpi/video/VGA/LCD/brightness would show that the level was set to 0 (though 20 was the lowest available). I was still able to control the brightness manually via /proc interface however. My investigations seem to indicate that HP, in their wisdom, seem to have removed the _BQC method from their BIOS code. It seems that the ACPI code in Linux that handles the key events to change the brightness use the _BQC method without checking for success, which explains why the level being set was garbage. However, the /proc interface for brightness seems to only use device->brightness->curr to get the current level. The attached patch, which I'm sure isn't correct, fixes my problems by making use of the brightness->curr field to track the current brightness. I'd love to know your opinion(s) on the problem and a proper fix (including perhaps sysfs backlight support?). Thanks, Ryan -- Ryan May Graduate Research Assistant School of Meteorology University of Oklahoma
--- video.c.old 2007-08-16 14:20:14.000000000 -0500 +++ video.c 2007-08-16 18:02:23.000000000 -0500 @@ -380,7 +380,7 @@ arg0.integer.value = level; status = acpi_evaluate_object(device->dev->handle, "_BCM", &args, NULL); - + device->brightness->curr = level; printk(KERN_DEBUG "set_level status: %x\n", status); return status; } @@ -392,7 +392,11 @@ int status; status = acpi_evaluate_integer(device->dev->handle, "_BQC", NULL, level); - + if (status) + *level = device->brightness->curr; + + printk(KERN_DEBUG "get_level status: %x\n", status); + status = 0; return status; }
