[RFC][ide] simplification of probing for default interfaces

[RFC][ide] simplification of probing for default interfaces

[Bartlomiej Zolnierkiewicz]

Hi,

Right now init_ide_data() (it is always called only once at ide driver startup)
calls init_hwif_data() for each hwif and then ide_init_default_hwifs().

- init_hwif_data() sets hwif->io_ports for all hwifs to architecture
  default values by calling ide_init_hwif_ports() for each hwif.
  However it does not set hwif->irq to the arch default one.

  These interfaces will be later probed (if not already found by some
  subdriver ie. ide pci) in ide_init_builtin_drivers() by calling
  ideprobe_init().

  Probing code will try to autodetect hwif's irq in try_to_identify()
  and if it fails it will fallback to using default irq in hwif_init().

- ide_init_default_hwifs() optionally (ie. for x86 it depends on
  #ifndef CONFIG_BLK_DEV_IDEPCI) does the same as init_hwif_data(),
  plus it sets hwif->irq to the default irq and also 'probes' for
  interface's presence by calling ide_register_hw().

  If ide is compiled-in, probing will be identical to the previously
  described for init_hwif_data().

  It ide is compiled as module this path is weird, because with first
  ide_register_hw() call ide-probe module will be loaded and all
  interfaces will be immediately probed. First one with default irq
  and others with irq autodection. On second ide_register_hw() call,
  second default interface will be probed with default irq etc.

  Note that if ide_init_default_hwifs() is used and interface doesn't
  use default irq, probing code will fail.

Conlusion is following:

ide_init_default_hwifs() does exactly what init_hwif_data() already does
(both for compiled-in and module case) with exception that it also sets
hwif->irq, but this is really not a problem since if irq autodection fails,
driver will fallback to using arch specific default irq.

What I propose is to kill ide_init_default_hwifs() and rely on irq
autodection + fallback code in ide-probe.c. This requires splitting
ide_init_default_hwifs() to ide_default_io_base() and ide_default_irq()
for some arm subarchs and breaking (or making it special case) arm/arch-sa1100
as its author though it was a good place to put hardware init code.

Are there any problems with such approach?
Am I missing something important in my understanding?

--
Bartlomiej

Re: [RFC][ide] simplification of probing for default interfaces

[Alan Cox]

On Iau, 2003-05-15 at 20:37, Bartlomiej Zolnierkiewicz wrote:
> ide_init_default_hwifs() does exactly what init_hwif_data() already does
> (both for compiled-in and module case) with exception that it also sets
> hwif->irq, but this is really not a problem since if irq autodection fails,
> driver will fallback to using arch specific default irq.

That sounds sensible, and the iops and other junk

> What I propose is to kill ide_init_default_hwifs() and rely on irq
> autodection + fallback code in ide-probe.c. This requires splitting

Remember the IRQ depends on the mode of the device (legacy v PCI native)
plus some chip specific constraints on pairing.

> ide_init_default_hwifs() to ide_default_io_base() and ide_default_irq()
> for some arm subarchs and breaking (or making it special case)

PA RISC also requires it can override default irq, and wants to know if
the device is the primary or secondary.