[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