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[Xen-devel] Re: [RFC PATCH 24/33] Add support for Xen event channels.

To: Chris Wright <chrisw@xxxxxxxxxxxx>
Subject: [Xen-devel] Re: [RFC PATCH 24/33] Add support for Xen event channels.
From: ramsdell@xxxxxxxxx (John D. Ramsdell)
Date: 18 Jul 2006 07:41:54 -0400
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I read with interest your patch for adding support for Xen event
channels.  I notice that evtchn.h uses an int to represent a port, as
demonstrated, for example, in the following two declarations:

> +extern void mask_evtchn(int port);
> +extern void unmask_evtchn(int port);

Using a signed integer is good because negative numbers can be use to
return error conditions from functions that cannot be confused with
valid port numbers.

For code used within Mini-OS, I've been using evtchn_port_t, which is
defined in xen-unstable/xen/include/public/event_channel.h as:

  typedef uint32_t evtchn_port_t;

Is there a plan to harmonize this representation of a port with yours,
and make it a signed integer?

I also notice that xen-unstable/xen/include/public/grant_table.h
defines grant_ref_t and grant_handle_t to be unsigned.  Once again,
having a representation of these items that unambiguously represent
error codes and not valid data seems to me to be very useful.


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