need help to understand piece of the doc

[Stefan Kalkowski]

Hi Naiji,

On 09/01/2017 03:39 PM, Naiji Ma wrote:
> Hi everybody,
> 
> 
> I would like to quote part of the official doc from [1]:
> 
> /As illustrated in the figure, from an organizational point of view, a
> virtual machine is implemented as a leaf node in Genode's process tree.
> Genode not only facilitates the use of virtual machines for application
> compatibility but also the re-use of existing device drivers. The baby
> Tux in the figure symbolizes an original Linux device driver being
> executed in a device-driver environment./
> 
> 
> [1] http://genode.org/documentation/general-overview/index
> 
> 
> How to understand the 're-use' ?  Does it mean that an
> original(unmodified) Linux device driver could be placed into a
> 'device-driver environment' and also function correctly in Genode, or
> does it mean an original Linux device driver could be taken out from the
> Linux virtual machine (the big Tux) and executed as a leaf node in
> Genode, consequently serve Genode as well as the big Tux at the same time? 
> 

The cited section explains the variety of approaches to re-use software
in Genode, either by using a complete OS as foundation to run existing,
unmodified applications, or to re-use a part of an existing OS like
Linux in form of a device driver. The latter is typically done by using
unmodified source files from an open-source OS together with a thin
library - the corresponding 'device-driver environment' tailored for
that specific driver.

So to re-use device drivers we take the first approach that you described.

Anyway, it is also possible in Genode to allow a virtual machine to
access dedicated peripherals exclusively. Thereby the guest OS drives
and makes use of the device. Nonetheless, I do not know of any existing
Genode scenario where components, which run aside from a
virtual-machine, make use of such a dedicated device driven by the guest
OS, although this would be possible in theory. In contrast, we generally
favour to keep the TCB of device driver small.

I hope this clarifies your question.

Regards
Stefan

> 
> Regards,
> Naiji
> 
> 
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-- 
Stefan Kalkowski
Genode Labs

https://github.com/skalk · http://genode.org/