# [SOLVED] Strange warning when building gentoo-2.6.39-r3

## RazielFMX

This may have been here for awhile, I am rebuilding my kernel to turn on a bunch of USB debugging options to try and figure out why something is not working an happened to notice it:

```
warning: (DRM_RADEON_KMS && DRM_I915 && STUB_POULSBO && FB_BACKLIGHT && PANEL_SHARP_LS037V7DW01 && PANEL_ACX565AKM && USB_APPLEDISPLAY && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_ASUS && ACPI_CMPC) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT)
```

Any thoughts on how to fix this?  Should I bother?

Thanks!Last edited by RazielFMX on Fri Sep 09, 2011 7:49 pm; edited 1 time in total

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## Thistled

Looks like you need to uncheck Backlight support or the likes in your kernel config. (or play around with it)

Device Drivers >

 Graphics Support >

  Backlight & LCD device support

It also looks like you may need to uncheck some parts of

Device Drivers >

 X86 Platform specific Device Drivers

```
ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_ASUS && ACPI_CMPC
```

suggests all these laptops have been selected. Which is wrong.

However, if it's not borking your system, I can't see no harm.

If it is preventing your kernel from building, then further detective work may be required.

Just my 2 pennies worth.

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## krinn

my assumptions could be wrong, but for me, that's something you should dig

here what i think is going on:

kernel is telling you a direct dependency is not met (the HAS_IOMEM && BACKLIGHT_LCD_SUPPORT) and it's a dependency need by DRM_RADEON or any of the other in the list.

This mean one of this module will not work correctly because of the missing dep, so yes, it's something you should dig out, just to see who will be affect.

And for me i will gave HAS_IOMEM a real high level of priority because of the name.

And yes this could happen if one edit the kernel by hand and setting a module (to y or m), else the kernel would have gray out the option until the missing dep is met.

It could also happen if devs miss that dep relationship within the kernel, but i more doubt that

And it could happen i suppose if an indirect dep remove a direct dep and kernel have no chance to recheck it (as a stupid example: selecting DRM_RADEON, kernel select then IO_MEM, you then select KERNEL_SOMETHING and kernel unselect IO_MEM because incompatible with KERNEL_SOMETHING, leaving you with IO_MEM missing for DRM_RADEON). I'm sure not kernel have a check for that kind of indirect depency removing a direct one.

Did you select an option by hand ? (that's just to know, even you didn't it's then a bug, but it's something you should dig). There's also a high chance the kernel build will fail, a small one nothing happen and a small one (the worst case) that all build ok, but the running module will fail.

And the better fix would be selecting IO_MEM & BACKLIGHT_LCD_SUPPORT

still if my assumptions are right...

anyway as a more generic answer to your question what would you answer to "The heart that makes my distro boot and run is telling me something is not as it should: should i bother ?"

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## RazielFMX

Checking the actual physical config shows its DRM_RADEON_KMS that's bringing this in:

```

nightshade linux # egrep 'DRM_RADEON_KMS|DRM_I915|\

STUB_POULSBO|FB_BACKLIGHT|PANEL_SHARP_LS037V7DW01|\

PANEL_ACX565AKM|SB_APPLEDISPLAY|ASUS_LAPTOP|\

SONY_LAPTOP|THINKPAD_ACPI|EEEPC_LAPTOP|ACPI_ASUS|\

ACPI_CMPC' .config

CONFIG_DRM_RADEON_KMS=y

# CONFIG_STUB_POULSBO is not set

# CONFIG_FB_BACKLIGHT is not set

# CONFIG_USB_APPLEDISPLAY is not set

nightshade linux # egrep 'BACKLIGHT_CLASS_DEVICE|HAS_IOMEM|BACKLIGHT_LCD_SUPPORT' .config

# CONFIG_BACKLIGHT_LCD_SUPPORT is not set

CONFIG_BACKLIGHT_CLASS_DEVICE=y

CONFIG_HAS_IOMEM=y

nightshade linux # 

```

So I think all I need to do it turn on BACKLIGHT_LCD_SUPPORT.

```

nightshade linux # egrep BACKLIGHT .config

# CONFIG_FB_BACKLIGHT is not set

# CONFIG_BACKLIGHT_LCD_SUPPORT is not set

CONFIG_BACKLIGHT_CLASS_DEVICE=y

nightshade linux # 

```

I do find it strange that when DRM_RADEON_KMS brings in BLACKLIGHT_CLASS_DEVICE, the downstream deps are not selected.

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## RazielFMX

I enabled BACKLIGHT_LCD_SUPPORT, and changed low level lcd support from M (defaulted to this on enable of BACKLIGHT_LCD_SUPPORT) to * and chose the generic LCD driver.  Warnings are gone and nothing broke when I turned these things on, so I'm satisfied.

I would like for menu based kernel config to be smart enough to enable downstream dependencies, but at least I got a warning!

As a side note, I had no problem building the kernel with the warnings, they just bothered me   :Very Happy: 

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