What's needed for a PCIe card to be recognized?

["Hans-Jürgen Koch" <hjk@linutronix.de>]

I'm playing around with a vanilla 2.6.25-rc1, adding patches to make it
work on an Asus EeePC. That one has the problem that its Mini PCIe WLAN
module doesn't show up in lspci. That brought up a few questions that I
couldn't answer yet:

How can they "hide" a PCIe card?
What could be their motive to do that?
How can I make it appear?

I found some solutions googling around, but they all seem to be funny
workarounds, like unloading pciehp and then loading it again with
pciehp_force=1, then switching WLAN off and on again
(through /proc/acpi/asus/wlan, I've got that one meanwhile)... This
doesn't look like a clean solution to me, but I must admit that I don't
know enough about PCIe hotplug to understand what's going on. I'd
appreciate it if someone could give me a few hints or point me to good
documentation.

Output of lspci:
00:00.0 Host bridge: Intel Corporation Mobile 915GM/PM/GMS/910GML Express Processor to DRAM Controller (rev 04)
00:02.0 VGA compatible controller: Intel Corporation Mobile 915GM/GMS/910GML Express Graphics Controller (rev 04)
00:02.1 Display controller: Intel Corporation Mobile 915GM/GMS/910GML Express Graphics Controller (rev 04)
00:1b.0 Audio device: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) PCI Express Port 1 (rev 04)
00:1c.1 PCI bridge: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) PCI Express Port 2 (rev 04)
00:1c.2 PCI bridge: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) PCI Express Port 3 (rev 04)
00:1d.0 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #1 (rev 04)
00:1d.1 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #2 (rev 04)
00:1d.2 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #3 (rev 04)
00:1d.3 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #4 (rev 04)
00:1d.7 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB2 EHCI Controller (rev 04)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev d4)
00:1f.0 ISA bridge: Intel Corporation 82801FBM (ICH6M) LPC Interface Bridge (rev 04)
00:1f.2 IDE interface: Intel Corporation 82801FBM (ICH6M) SATA Controller (rev 04)
00:1f.3 SMBus: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) SMBus Controller (rev 04)
03:00.0 Ethernet controller: Attansic Technology Corp. L2 100 Mbit Ethernet Adapter (rev a0)

(The WLAN card should show up at 01:00.0, according to info found on
the web).

Thanks,
Hans