Re: Questions about the device driver framework

[Vittore Scolari]

Daniel Wagner wrote:

> > Why there is the need for a virtual driver?
> >    
>
> The ddf should not have knowlegde about the OS which is using it.  So
> the real driver can't implement OS dependent code.
>
>  
>
> > Can't deva, which is OS dependent, trust access to drivers?
> >    
>
> It could but that would serialize all access through deva ->
> bottleneck.  As soon the real driver trusts a virtual driver they can
> communicate without the help of deva.
>
>  
Yes, but i don't understand why deva would be a bottleneck. If the ddf 
would be a library on top of deva (better if there would be a deva for 
each driver) then deva could be thin and really fast.

Also this would make ddf easier to port on different (l4?)-os. You would 
just write a replacement for deva, no need for a virtual driver for 
every os.

Of course, the more ddf is portable, the more it is difficult to 
implement it efficently. There must be libraries for replacement of:
- c standard functions
- memory menagement (also for mapping buffers from users)
- security (p.e. entropy)
- trust
- drivers interfaces

And all this libraries (that we can call deva) shouldn't rely on 
os-dependant facilities, because there could be not.

Having deva as a library can also give a fast way to use os resources if 
they exists.


Thanks,
Vittore