building 2.3.36+ I ran in to an 'unmet direct dependensie':

cd /usr/src/linux-2.6
make ARCH=i386 O=/usr/src/psion oldconfig

   GEN     /usr/src/psion/Makefile
scripts/kconfig/conf --oldconfig Kconfig
warning: (FB_BACKLIGHT && HAS_IOMEM && FB || DRM_I915 && <choice> && 
AGP_INTEL && ACPI || PANEL_SHARP_LS037V7DW01 && HAS_IOMEM && OMAP2_DSS 
|| PANEL_ACX565AKM && HAS_IOMEM && OMAP2_DSS && OMAP2_DSS_SDI && SPI || 
USB_APPLEDISPLAY && USB_SUPPORT && USB || ASUS_LAPTOP && X86 && 
X86_PLATFORM_DEVICES && ACPI && !ACPI_ASUS && INPUT && (RFKILL || 
RFKILL=n) || SONY_LAPTOP && X86 && X86_PLATFORM_DEVICES && ACPI && INPUT 
&& RFKILL || THINKPAD_ACPI && X86 && X86_PLATFORM_DEVICES && ACPI && 
INPUT && (RFKILL || RFKILL=n) || EEEPC_LAPTOP && X86 && 
X86_PLATFORM_DEVICES && ACPI && INPUT && EXPERIMENTAL && (RFKILL || 
RFKILL=n) && HOTPLUG_PCI || ACPI_ASUS && X86 && X86_PLATFORM_DEVICES && 
ACPI || ACPI_CMPC && X86_PLATFORM_DEVICES && X86 && ACPI && (RFKILL || 
RFKILL=n)) selects BACKLIGHT_CLASS_DEVICE which has unmet direct 
dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT)
warning: (FB_BACKLIGHT && HAS_IOMEM && FB || DRM_I915 && <choice> && 
AGP_INTEL && ACPI || PANEL_SHARP_LS037V7DW01 && HAS_IOMEM && OMAP2_DSS 
|| PANEL_ACX565AKM && HAS_IOMEM && OMAP2_DSS && OMAP2_DSS_SDI && SPI || 
USB_APPLEDISPLAY && USB_SUPPORT && USB || ASUS_LAPTOP && X86 && 
X86_PLATFORM_DEVICES && ACPI && !ACPI_ASUS && INPUT && (RFKILL || 
RFKILL=n) || SONY_LAPTOP && X86 && X86_PLATFORM_DEVICES && ACPI && INPUT 
&& RFKILL || THINKPAD_ACPI && X86 && X86_PLATFORM_DEVICES && ACPI && 
INPUT && (RFKILL || RFKILL=n) || EEEPC_LAPTOP && X86 && 
X86_PLATFORM_DEVICES && ACPI && INPUT && EXPERIMENTAL && (RFKILL || 
RFKILL=n) && HOTPLUG_PCI || ACPI_ASUS && X86 && X86_PLATFORM_DEVICES && 
ACPI || ACPI_CMPC && X86_PLATFORM_DEVICES && X86 && ACPI && (RFKILL || 
RFKILL=n)) selects BACKLIGHT_CLASS_DEVICE which has unmet direct 
dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT)
#
# configuration written to .config
#

BACKLIGHT_LCD_SUPPORT was set to 'n'. make menuconfig does not force me 
to set this setting.

-- 
Hans