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For one of my pci device, output of lspci -vvv says pin A routed to 19. but output of lspci -b -vvv gives 255. All the pci devices gives irq 255 in lspci -b -vvv, while for lspci -vvv it gives different numbers. Can anyone please explain this?

Savan
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  • *-b Bus-centric view. Show all IRQ numbers and addresses as seen by the cards on the PCI bus instead of as seen by the kernel.* So, what exactly are you trying to achieve? – 0andriy Jun 06 '17 at 19:17
  • I am asking that it is ok that all devices show irq 255 in bus centric view. – Savan Jun 07 '17 at 04:39
  • PCI interrupts are out-of-band signals, so what do you expect to see? – CL. Jun 07 '17 at 09:33
  • @CL I guess it also depends on HW architecture (PIC + PIR) used on certain platform. I just run the above on x86 and got the numbers kinda ISA range, and not 255. – 0andriy Jun 07 '17 at 10:32
  • When we add -b in lspci it gives us the irq no which seen from the device. where in actual lspci output it is virtual irq number. – Savan Aug 08 '17 at 09:56

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When you insert -b in lspci command it will gives you the interrupt number seen by the device. So this interrupt number will be hardware interrupt number. Without -b, it will give you virtual interrupt number. So these both number will be different.

JoeFerns
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