On 20-08-08 06:50, Rajat Jain wrote:
On 19-08-08 07:11, Rajat Jain wrote:
I want to understand who decides the IRQ number that a agiven PCI
card will use. I understand that from a PCI device drivers point of
view, it'll find the IRQ vector that it needs to attach by reading
it from the configuration space of the device.
Actually, a quick look at struct pci_dev suggests you should
be using pci_dev->irq. Note sure why that is; maybe odd
bridged setups.
Where in source code is pci_dev->irq getting populated? I tried but
could not exactly locate it...
pci_read_irq() it seems.
OK. But who does it in an embedded environment (PPC for eg) where
there is no POST software. The first piece of code that gets executed
is U-boot and then the kernel. So who writes the LINE value into the
config space?
If anything, the kernel and specifically that bit of the kernel that
sets up the routing (if there is anything to setup; might ofcourse be
fully hardwired there).
The "if anything" might be the reason for needing to use pci_dev->irq as
per the comment. As said, don't know. Makes sense though; why would you
write it back to config space if you can just supply it as part of pci_dev.
Rene.
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