Re: [PATCH 4/5] Centralise NO_IRQ definition

From: Matthew Wilcox (matthew_at_wil.cx)
Date: 11/22/05

  • Next message: Al Viro: "Re: [PATCH -mm2] net: Fix compiler-error on atyfb_base.c when !CONFIG_PCI" 
    Date:	Mon, 21 Nov 2005 19:45:10 -0700
To: Linus Torvalds <torvalds@osdl.org>

    On Mon, Nov 21, 2005 at 01:49:45PM -0800, Linus Torvalds wrote:
    > On all PC hardware, having a zero in the PCI irq register basically means
    > that no irq is enabled. That's a _fact_. It's a fact however much you may
    > not like it. It's how the hardware comes up, and it's how the BIOS leaves
    > it. So "0" absolutely does mean "not allocated".

    Actually, no. Here's my x86 laptop's config space ...

    0000:02:06.2 System peripheral: Texas Instruments PCI1620 Firmware Loading Function (rev 01)
            Subsystem: Hewlett-Packard Company: Unknown device 08b0
            Flags: bus master, medium devsel, latency 64
            I/O ports at 4000 [size=64]
            Capabilities: [44] Power Management version 2
    00: 4c 10 01 82 07 01 10 02 01 00 80 08 08 40 00 00
    10: 01 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    20: 00 00 00 00 00 00 00 00 00 00 00 00 3c 10 b0 08
    30: 00 00 00 00 44 00 00 00 00 00 00 00 ff 00 07 04

    Interrupt Pin is 0x3d and Interrupt Line is 0x3c. As I explained earlier,
    Linux simply never reads Interrupt Line if Interrupt Pin is 0.

    Anyway, this doesn't matter too much. I don't personally care about
    NO_IRQ being 0 or -1; that was something benh tried to make me care
    about ;-)

    So, how about this for a new patch series:

     - Patch 1, same as this series (it just makes sense to bounds-check in
       the irq management functions).
     - Patch 2, add #ifndef NO_IRQ #define NO_IRQ 0 #endif to linux/hardirq.h
     - Patch 3, set dev->irq to NO_IRQ in drivers/pci/probe.c
     - Patch 4, remove custom definition of NO_IRQ from pd6729
     - Patch 5, use NO_IRQ in serial_core

    I'll start work on that now, since that fixes the problems I care about
    and doesn't negatively affect people with problems I don't care about ;-)
    -
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