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    SubjectRe: [RFC] killing the NR_IRQS arrays.
    Date
    On Tuesday 27 February 2007, Eric W. Biederman wrote:
    > * Add a variation of the API in interrupt.h that uses
    >   "struct irq *irq" instead of "unsigned int irq"
    >  
    >   Probably replacing request_irq with irq_request or something
    >   trivial like that.
    >
    >   This will need to touch all of different irq implementation back
    >   ends, but only very lightly.
    >
    > * Convert the generic irq code to use struct irq * everywhere it
    >   current uses "unsigned int irq".
    >
    > * Start on the conversions of drivers and subsystems picking on
    >   the easy ones first :)

    Introducing the irq_request() etc. functions that take a struct irq*
    instead of an int sounds good, but I'd hope we can avoid using those
    in device drivers and do a separate abstraction for each bus_type
    that deals with interrupts. I'm not sure if that's possible for
    each bus_type, but the ones I have worked with in the past should
    allow that:

    pci: each device/function has a unique irq, drivers need not know
    about it afaics.
    isa/pnp: numbers from 1 to 15 are the right abstraction here, that
    how isa has worked for ages.
    s390: got rid of irq numbers already
    ofw: an open firmware device can have a number of interrupts, but
    like PCI, the driver only needs to know things like 'first
    irq of this device', not how it's connected
    ps3: irqs are requested from the firmware for each device, this
    can happen under the covers.
    mmc, usb, phy, ieee1394: these already have a higl-level abstraction
    for interrupt events
    platform: dunno, probably these really should use the struct irq
    directly
    eisa, mca, pcmcia, zorro, ...: no idea, but possibly similar to PCI.

    Note that we can even start converting device drivers first, before
    moving away from irq numbers. A typical PCI driver should get
    somewhat simpler by the conversion, and when they are all converted,
    we can replace pci_dev->irq with a struct irq* under the covers.

    Arnd <><
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