[9fans] more "Plan 9 from Bell Labs" questions

[paurea@gmail.com (Gorka Guardiola)]

On Mon, Apr 4, 2011 at 11:36 AM, faif <faifgnu at gmail.com> wrote:
> "9P has two forms: RPC messages sent on a pipe or network connection
> and a procedural interface within the kernel. Since kernel device
> drivers are directly addressable, there is no need to pass messages to
> communicate with them;"
>
> Are the device drivers really in kernel space? It seems that Plan 9 is
> an ideal design for moving buggy software like 3rd party drivers into
> the user space.
>

Some of them are. Vga is, for example, usb is half in (usbd), half out
(usb/disk). Whenever possible it is better to have things in user space
(protection, easy to debug, etc). Sometimes for efficiency reasons it
is better inside (less context switches, no marshalling of 9P etc.).

> Just wondering if anybody has worked on the TODO things mentioned in
> the paper:
>
> "Using streams to implement network interfaces in the kernel allows
> protocols to be connected together dynamically, such as to attach the
> same TTY driver to TCP, URP, and IL connections, but Plan 9 makes no
> use of this configurability."
>

I am guessing this is why there are no streams any more :-).

> "Although Plan 9 has per-process name spaces, it has no mechanism to
> give the description of a process?s name space to another process
> except by direct inheritance."
>
>

There is no way to do this now in plan 9 as it is AFAIK.
The best you can try to do is get the namespace /proc/*/ns and try to recreate
it which is not exactly the same.

G.