Link/Links field in struct device

[Eric W. Biederman]

Li-Ta Lo <ollie at lanl.gov> writes:

> Eric,
> 
> What does the link field in the device struct used for ? Does
> it has anything to do with the hypertransport links ? 

Yes, and no. 

In the device tree each device has several links coming off of it.  One
for each function.    So below mc0 has 6 logical links:
	pci 0:18.0
	pci 0:18.0
	pci 0:18.0
	pci 0:18.1
	pci 0:18.2
	pci 0:18.3

You can only hang devices off of the first 3 which are the hypertransport
links, in this case.  Hanging devices off the rest is not physically possible.
I do abuse HT chains a little bit an consider all of their members hanging
off the start of the chain instead of hanging off of each other.  But that
seems to model the reality fairly well.


> Is there a way to travel the HT links like the PCI bus in LinuxBIOS ?

Yes.  A HT chain is treated as a bus.  And we rebuild the chains during
enumeration.


> 
> Ollie

northbridge amd/amdk8 "mc0"
	pci 0:18.0
	pci 0:18.0
	pci 0:18.0
	pci 0:18.1
	pci 0:18.2
	pci 0:18.3
	southbridge amd/amd8131 "amd8131" link 0
	end
	southbridge amd/amd8111 "amd8111" link 0
	end
end