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Re: Questions about the device driver framework

From: markus kaarn
Subject: Re: Questions about the device driver framework
Date: Thu, 20 Jan 2005 20:25:11 -0600
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20040618

Vittore Scolari wrote:

Daniel Wagner wrote:

A virtual driver is a driver which is on top of a real driver.  The
virtual driver is port of the operating system and forwards all
request to the real driver.  The virtual driver has an access control
list which is OS dependend of course.  The real driver then has only
to trust one thread, the virtual driver.

I have some questions:
Why there is the need for a virtual driver?

Maybe so that i.e. linux driver can be taken, and used
in Hurd(without significant changes), but before it can
be used there, the virtual driver interface written, trough
which driver controlled device can be accessed.

Can't deva, which is OS dependent, trust access to drivers?
Does all drivers trust each other?

They should not. Why should they? Every device driver define
interface and the way it can be used. No matter who accesses
driver, the interface to it is same for everybody.

Anybody, am i wrong here? So i wouldn't made one think wrong.

How a bus driver serve and trust device drivers?

I'm dizzy a bit here. Bus-driver(as i see it) registers a device driver,
gives resources of device, and total control of device to that driver.
As i see it now, bus-driver only registers device-driver to specific
device. So no other device-driver can register, or pretend for this
device as long as first driver is registered/loaded.
Mmm.. now here i can't say how Bus-Driver can prevent malicious
driver to be registered.



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