Update _index.adoc

[onetruemike]

Corrected nvidia BusID in 20-drivers.conf to match the output of the previous pciconf command.

[onetruemike]

Proposed change to have the output of the pciconf command match the BusID in 20-drivers.conf to avoid the confusion from this forum thread https://forums.freebsd.org/threads/clarification-on-pci-busid-in-https-docs-freebsd-org-en-books-handbook-x11-x-config-gpu.102143/

[concussious]

Hey, thanks for the patch. Unfortunately, I have seen all types of values for that string in the wild, so I don't think this makes it any clearer.

If you think we can make it clearer, maybe we can explain it better instead?

[onetruemike]

It just needs to be explained that the BusIDs in 20-drivers.conf should be the same as the output of pciconf -lv | grep -B3 display despite the example 20-drivers.conf showing two different BusIDs for nvidia.
It's confusing because the example 20-drivers.conf doesn't say where the nvidia BusID "pci0:0:2:1" came from since the previous example's output shows pci0:1:0:0.

The instructions could be clarified to say:

The output should be similar to the following:

vgapci0@pci0:0:2:0:     class=0x030000 rev=0x0c hdr=0x00 vendor=0x8086 device=0x46a6 subvendor=0x1028 subdevice=0x0b29
    vendor     = 'Intel Corporation'
    device     = 'Alder Lake-P GT2 [Iris Xe Graphics]'
    class      = display
--
vgapci0@pci0:1:0:0:     class=0x030200 rev=0xa1 hdr=0x00 vendor=0x10de device=0x25b9 subvendor=0x1028 subdevice=0x0b29
    vendor     = 'NVIDIA Corporation'
    device     = 'GA107GLM [RTX A1000 Laptop GPU]'
    class      = display

Example 6. Select Intel® Graphics Driver and NVIDIA® Graphics Driver in a File
/usr/local/etc/X11/xorg.conf.d/20-drivers.conf

Section "Device"
	Identifier "Card0"
	Driver     "intel"
	BusID     "pci0:0:2:0"
EndSection

Section "Device"
	Identifier "Card1"
	Driver     "nvidia"
	BusID     "pci0:0:2:1" #This should be the same value you got from pciconf; in our example it was pci0:1:0:0
EndSection