[coyotos-dev] IPC Redesign

[Charles Landau]

At 3:03 PM -0400 5/22/07, Jonathan S. Shapiro wrote:
>On Tue, 2007-05-22 at 11:22 -0700, Charles Landau wrote:
>>  At 1:59 PM -0400 5/22/07, Jonathan S. Shapiro wrote:
>  > >On Tue, 2007-05-22 at 10:30 -0700, Charles Landau wrote:
>  > >  > I'm approaching this issue from the standpoint of compatibility with
>>  >>  CapROS. It would be a pity if programs written for one system were
>>  >>  difficult to port to the other because they use features that are not
>>  >>  available on the other system.
>>  >
>>  >This is the job of CapIDL.
>>
>>  Can I use CapIDL to write a transparent forwarder/proxy that will
>>  accept *any* message? How many data words does my proxy need to
>>  handle?
>
>No. CapIDL *explicitly* does not expose low-level representation. That
>isn't its job. The entire point of CapIDL is to isolate the user from
>the low-level representation. The policy decision is that interfaces are
>defined by their IDL, not by their transport-level protocol.
>
>Setting that aside, fully transparent forwarding is not possible in
>principle, because you need to know what the call/response protocol is,

Excuse me, but didn't the long discussion on cap-talk about membranes 
and such come to the opposite conclusion? And doesn't the Horton 
protocol involve a transparent forwarder? The only thing you need to 
know about the protocol is where the capabilities are.

>All that being said, my view is that the adoption of IDL strongly
>reduces the importance of this issue. Given an IDL specification, it is
>possible to automatically generate a forwarder for any given interface.

Yes, but for a *transparent* forwarder (assuming such a thing is 
possible), I don't see how CapIDL can help. And that is a pity, 
though perhaps not such a large one.