Custom kernel: /sys/class/backlight is empty (not empty with default)

jwhendy · 2011-10-11 00:01:15

I just compiled a 3.0.4 kernel and found that /sys/class/backlight is empty. The default x86_64 kernel fills this directory populates this directory properly. Any suggestions on why this might be the case?

$ lspci
01:00.0 VGA compatible controller: nVidia Corporation GT215 [Quadro FX 1800M] (rev a2)

Graphics support  --->
   < > /dev/agpgart (AGP Support)  ---> 
   -*- VGA Arbitration
   (16)  Maximum number of GPUs
   [ ] Laptop Hybrid Graphics - GPU switching support
   <*> Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)  --->
      [[No options selected in here, though]]
   < > Intel GMA500 Stub Driver
   < > Lowlevel video output switch controls
   <*> Support for frame buffer devices  --->
      -*-   Enable Video Mode Handling Helpers
      <M>   nVidia Framebuffer Support
      [*]     Support for backlight control
   -*- Backlight & LCD device support  --->
      -*-   Lowlevel Backlight controls
   Display device support  --->
   Console display driver support  --->
   -*- VGA text console
      [*]   Enable Scrollback Buffer in System RAM
      (64)    Scrollback Buffer Size (in KB)
      <*> Framebuffer Console support
   [*] Bootup logo  --->

Not sure what I'm missing. I would have figured that the nvidia framebuffer support and backlight control would do the trick. Any suggestions?

I've looked at other threads like THIS ONE and THIS ONE. They seem to be attempting to solve issues with the default kernel and employing things like nvidia-bl or adding lines to menu.lst. My difference is that the default kernel works fine with a custom script I have to directly change the contents of /sys/class/backlight/brightness and such. For whatever reason, this custom kernel is not producing the usual suspects in that directory.

Thoughts? Let me know if other input would be helpful.

Stebalien · 2011-10-11 15:43:34

Please upload your '.config'. Is CONFIG_BACKLIGHT_CLASS_DEVICE set?

jwhendy · 2011-10-11 16:12:05

@Stebalien Here's the config on pastebin

And yes, that option is set.

$ grep BACKLIGHT /boot/config-custom
CONFIG_FB_BACKLIGHT=y
CONFIG_FB_NVIDIA_BACKLIGHT=y
CONFIG_BACKLIGHT_LCD_SUPPORT=y
CONFIG_BACKLIGHT_CLASS_DEVICE=y
# CONFIG_BACKLIGHT_GENERIC is not set
# CONFIG_BACKLIGHT_PROGEAR is not set
# CONFIG_BACKLIGHT_APPLE is not set
# CONFIG_BACKLIGHT_SAHARA is not set
# CONFIG_BACKLIGHT_ADP8860 is not set
# CONFIG_BACKLIGHT_ADP8870 is not set
# CONFIG_LEDS_TRIGGER_BACKLIGHT is not set

Arch Linux

#1 2011-10-11 00:01:15

Custom kernel: /sys/class/backlight is empty (not empty with default)

#2 2011-10-11 15:43:34

Re: Custom kernel: /sys/class/backlight is empty (not empty with default)

#3 2011-10-11 16:12:05

Re: Custom kernel: /sys/class/backlight is empty (not empty with default)

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