On Wed, 9 Jul 2003, Linus Torvalds wrote:
> On Wed, 9 Jul 2003, Jeff Garzik wrote:
> > I'm curious where interrupts are re-enabled, though?
>
> The low-level drivers seem to do it at every IO. Don't ask me why. But it
> gets done automatically by any code that does
>
> hwif->OUTB(drive->ctl, IDE_CONTROL_REG);
>
> which is pretty common (just grep for "IDE_CONTROL_REG" and you'll see
> what I mean).
>
> I note that I should have made this "disable irq" be dependent on
> IDE_CONTROL_REG being non-zero. Although I don't see when that register
> _can_ be zero, it would be a major bummer not to have access to the
> control register.
>
> (Obviously it must be zero for some architecture, though, or those
> conditionals woulnd't make sense. Alan? Bartlomiej? What kind of sick
> pseudo-IDE controller doesn't have a control register?).
IDE can live without the control register (what do you _really_ need it for?).
Hence some hardware doesn't provide it, by leaving out the second bank of 8 IDE
registers.
Another trick is the `IDE doubler' for Amiga (but I guess you can make it work
on any IDE interface): with a few diodes you can map the second bank of 8 IDE
registers to a second IDE chain, doubling the number of devices you can
attach.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.orgIn personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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