nvidia_bl

[luigi.viggiano]

Hi.

I have a MacBook Pro 5.1 with Karmic. In my /etc/modules I have the nvidia_bl that I think is used to control backlight. But even if I remove the nvidia_bl from /etc/modules I can control the backlight using fn+f1/f2 and it works more gradually and more close to the gauge.

My questions are:
1. nvidia_bl, what is it? I googled around and I didn't find an satisfactory explanation.
2. Should I still use it with Karmic and my Mac 5.1 ?

I've upgraded from Jaunty to Karmic; if you see something wrong, please tell me:

cat /etc/modules
# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.

lp
rtc
coretemp
applesmc
bcm5974
usbhid
nvidia_bl

[_mario_]

I have a MacBook Pro 5.1 with Karmic. In my /etc/modules I have the nvidia_bl that I think is used to control backlight. But even if I remove the nvidia_bl from /etc/modules I can control the backlight using fn+f1/f2 and it works more gradually and more close to the gauge.

My questions are:
1. nvidia_bl, what is it? I googled around and I didn't find an satisfactory explanation.

nvidia_bl is a kernel-level driver that allows user-level applications (e.g. gnome-power-manager) to adjust screen backlight. basically, this is the same functionality as the mbp_nvidia_bl driver provides, with some subtle differences:

1. Interface: nvidia_bl drives the Nvidia graphics adapter's smartdimmer registers directly, which allows a more fine-grained control (1024 levels). It is not limited to Apple machines, but Nvidia graphics adapters.
   
   mbp_nvidia_bl, in contrast, uses a firmware interface present on recent Apple machines, that only provides 16 distinct levels. This is what Apple's bootcamp Windows drivers use as well. Having only 16 levels is most annoying in dark environments where 1024/16=64 is still too bright (I prefer to go down to 20, which also safes power). Despite it's name mbp_nvidia_bl also supports some Apple machines with Intel graphics chips, i.e. MacBook Air 1.
   
2. Loading: nvidia_bl cannot be loaded automatically by the kernel. That's why you have to put this line to /etc/modules. mbp_nvidia_bl will be loaded automatically, if a suitable device is present. You can check this by running:
   

   lsmod | grep nvidia_bl

3. Support: In theory both should work, but in practice on some machines the drivers fail, e.g. mbp_nvidia_bl on MacBook 5 / MacBook Air 2 (Geforce 9400M). Symptoms: Changing brightness simply does have no effect.

2. Should I still use it with Karmic and my Mac 5.1?

Use whatever you like. I'd prefer nvidia_bl over mbl_nvidia_bl, if it works on your machine

Please also note: These drivers only provide a sysfs-interface for user-level applications. If both drivers are loaded it's not exactly clear which one gets used (by gnome-power-manager). I addition, pommed (if you use it) uses the sysfs-interface and falls back to a built-in driver otherwise. In case of machines with Nvidia graphics adapter, this is the same firmware interface mbp_nvidia_bl uses.

bcm5974
usbhid

Why are you loading bcm5974 and usbhid manually? Doesn't your trackpad work out of the box?

ciao,
Mario