Xen devel - Dec 2003 - pcnet32 and copybreak condition

The main modifications in the PCnet32 ethernet driver seems to be macro that
test if COPYBREAK is define. I notice that for network driver which were written
for Xen the main modifications was around the copybreak and also some
adjustments with include files. Is it true if I say that the port of network
device from Linux to Xen is quite "easy" and that the majority of the
modifications are due to the differences with inlcude files and differences with
"copybreak" scheme? To be more clear, I don''t see why
it''s not possible to take
a native linux device driver and recompile it in Xen? Which mechanisms provided
by Linux are not provided by Xen (for exemple I saw the implementation of
function register_chrdev() in Xen so you can register character device using the
same interface as in Linux...). Why, for exemple, it isn''t possible to
implement
a copybreak mechanism in Xen? Will that imply a too major change?

You plan to move the management of device in domain0 using the native linux
device drivers right? Have you ever write something concerning what are the
differents steps that will allow to achieve this goal? 

Thank you very much for your help
Have a nice day 
Guillaume    


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> The main modifications in the PCnet32 ethernet driver seems to be macro
that
> test if COPYBREAK is define. I notice that for network driver which were
written
> for Xen the main modifications was around the copybreak and also some
> adjustments with include files. Is it true if I say that the port of
network
> device from Linux to Xen is quite "easy" and that the majority of
the
> modifications are due to the differences with inlcude files and differences
with
> "copybreak" scheme? 
Porting network drivers is usually straight forward. 

We could add a few more dummy header files to make the job even
easier, but since we''re planning on moving to a new IO scheme we
haven''t put much effort into this.

Areas of memory into which packets are received are not by
default mapped into Xen''s virtual address space, hence using the
CPU to memcpy the data (as in COPYBREAK) doesn''t work unless you
add a ''map_domain_mem'' call in front of it. The quick and easy
fix in the case of pcnet32 was just to disable COPYBREAK.

> You plan to move the management of device in domain0 using the native linux
> device drivers right? Have you ever write something concerning what are the
> differents steps that will allow to achieve this goal? 
I''m in the process of writing a document that describes the Xen
road map, and will post it to the list.

Best,
Ian


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