Your response helped, thanks.
Is the intent that userland cannot specify an event channel port number?
If so, is xen-store the proper way to communicate a port value between
domains? The latest event channel code appears to always allocate a
free port on behalf of the caller for both sides of an interdomain
channel. Older versions allowed the unbound end to specify a port
number.
Regarding port types:
Xen uniformly uses "int" for ports and computes port numbers < 0 as
invalid. This is all great. Userland code could be more consistent by
also using "int" throughout. Using u32 throughout usermode creates
problems for functions with overloaded +port/-error return values. Any
interest here?
Thanks for the help,
-steve
-----Original Message-----
From: Keir Fraser [mailto:Keir.Fraser@cl.cam.ac.uk]
Sent: Tuesday, October 11, 2005 2:18 AM
To: King, Steven R
Cc: xen-devel List
Subject: Re: [Xen-devel] suggested event channel cleanups
On 10 Oct 2005, at 23:50, King, Steven R wrote:
> This patch standardizes the type of "port" to "int" for
event channel
> functions and structures. Internally, Xen is using "int" for
ports,
> but userland code has a mix of "int" and "u32". Type
"int" is
> preferred in userland, since some functions want to return a positive
> port value or a negative error code.
Userspace may do this, but Xen doesn''t. It makes sense to give those
fields an unsigned type because Xen will never return a negative value.
If higher-level interfaces outside Xen return a signed type, with -ve
indicating error, there''s no reason for Xen to do the same.
> xenctrl.h: Added extern "C" to allow linking with C++ programs.
Isn''t it quite normal to put the ''''extern
"C"'' in the C++ program itself
when including C header files?
> xenctrl.h: Added function prototype for event channel close.
> xenctrl.h: Added function prototype for interdomain event channel.
These were removed last week.; The correct interface for user-space
programs is now ioctls via /dev/xen/evtchn. See examples of its use in
console/daemon/io.c, for example.
> I''ve never offered up a patch before, so apologies if I''m
abusing
> conventions.
There''s nothing wrong with the format of the patch. :-)
-- Keir
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