/proc/pci deprecation?
Quoted 4 lines · Linus Torvalds
- we should _never_ update the
PCI_INTERRUPT_LINEregister, because it destroys boot loader information (the same way we need to not overwrite BIOS extended areas and ACPI areas etc in order to be able to reboot cleanly)
I don't think the kernel presently does this, but if it
were to actually do the chipset-specific programming change the IRQ routing of a device, it should update PCI_INTERRUPT_LINE precisely so that the information will be passed on across a soft reboot.
This comes up for me because I have daone motherobard with a
BIOS that never programs the USB controller's interrupt line, so I have to do the chipset-specific bit twiddling (which, in this case happens to be simply writing the desired irq into the device's PCI_INTERRUPT_LINE register anyhow). By the way, I also had to change arch/i386/kernel/pci.c to get it to reread PCI_INTERRUPT_LINE if it thought the interrupt was not routed, although all that I would really need is some way for a user level program to persuade the kernel to believe that a particular PCI device's interrupt line A has changed to irq n.
This exception is probably not relevant to what Linus and
Richard are discussing, but I thought should mention it, lest that "_never_" be interpreted too absolutely.
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