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Re: update on the device driver framework

From: Marcus Brinkmann
Subject: Re: update on the device driver framework
Date: Thu, 28 Aug 2003 14:06:51 +0200
User-agent: Mutt/1.5.4i

On Tue, Aug 26, 2003 at 09:34:50PM +0200, Peter 'p2' De Schrijver wrote:
>   Only threads which have registered as trusted are allowed to access
>   device drivers.  The checks is simple done by checking the senders
>   id against a table of known threads.

There is a simple way to do it in O(1) anyway.  Require the user to supply
the index in the table.  So if a user sends a message foo (5, something),
then lookup entry 5 in the table (after performing a range check of course)
and check if the sender thread ID matches.

This way you don't have to worry about the number of threads being
registered.  Only insertion can take a bit longer if you look for deleted
entries.  But that should be ok.

> * Device Drivers
> ** Classes
>   - character: This the standard tty as known in the Unix environment.

I am not sure you want full tty functionality, though.  A minimal interface
that allows to implement the rest on top of it, as Wagi did for OSKit,
should be ok, I think.

But I am not sure what the purpose of these classes is.

> *** IRQ priorities
>   All IRQs on L4 have priorities, so if an IRQ occurs any IRQ lower
>   then the first IRQ will be blocked until the first IRQ has been
>   acknowlegded.  ISR priorities must much the hardware priority
>   (danger of priority inversion).  Furthermore the IRQ acknowledgment
>   order is important.

"must much" -> "must match"

`Rhubarb is no Egyptian god.' GNU      http://www.gnu.org    address@hidden
Marcus Brinkmann              The Hurd http://www.gnu.org/software/hurd/

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