Re: Ada OS Kernel features

["chris.danx" <chris.danx@ntlworld.com>]

> > You should be able to load/unload a driver dynamically (I hate rebooting
> > because of driver change).
>
> Agreed.  This is not simple to implement, but it is well worth the trouble
>
> > You should be able to "overload" a driver. What I mean ?  Lets assume
> > you have a simple grafic driver on bootup, then you load a "better"
> > (more complex, higher resolution, 3D excelerator ...) one. If this one
> > crashes, then it should simply be unloaded and the system should
> > continue work with the (simple) default driver - instead of showing a
> > "blue screen" ;-)
>
> My first reaction to this was "Not Possible".  However, that isn't
entirely
> true; it is just *VERY VERY* difficult.

Only in the "drivers in supervisor mode" model.

> A driver runs in kernel mode,

Why?  Why not just have it in user mode?  It makes more sense to have them
in user mode, at least to me.  They can only corrupt themselves then, etc.

> and has access to system data structures.

Why should it?  In your model a driver can screw a system up good and
proper, but if you put the driver in user mode then the associated problems
go away.  New ones do crop up, but there's ways and means to deal with them.


> If a driver corrupts a system data structure, how do you detect this,
repair it, and continue?

I really don't get why a driver must have access to system structures or
atleast those in kernel space, can you explain this?