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Re: oskit driver for i8042 keyboard controller

From: Roland McGrath
Subject: Re: oskit driver for i8042 keyboard controller
Date: Fri, 8 Nov 2002 14:51:29 -0500 (EST)

> This is an interesting strategy.  Long ago, I recall there being
> devices on a Vax that you couldn't reliably probe this way, because
> the bus could hang for several seconds during the probe for various
> reasons.  

In practice, the probe always happens very early.  The first time a
device_open is done for the root disk, that probes the root bus and that
recurses on the busses for controllers it finds and so forth.

Anyway, this kind of question is for the device manager thingie to worry
about in the long run.  Conceptually, the kernel should not be thinking
about peripheral hardware, and the device interfaces in oskit-mach are just
a makeshift solution putting in the kernel what only works in the kernel
right now, and a Hurdish user-level layer should cover the ugly innards.

> It also prevents the auto-detection of interrupt number, doesn't it?
> You'd have to turn off all other interrupts, and tickle the device.

This is the business of the driver to figure out, in the oskit interfaces.
It doesn't really have to turn off all interrupts, it can just install its
special probe interrupt handler on all the canditate irqs that are not
already taken by other devices that won't share.

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