RPC parameters

[Norman Feske]

Hello,

> Genode is new to me . I just start playing with it. 

welcome to the list!

> I was looking  at the Hello program and the RPC mechanism.  as i
> understood RPC does not support passing pointer as parameter 
> how i can pass a parameter by reference where i need to change its value
> in the server side. 

you can find a detailed description of the RPC mechanism in Section
8.12. "Remote procedure calls" of the manual [1]. In short, you have two
options:

1. Define a POD struct used as return type of your RPC functiion.
   For an example, take a look that the Framebuffer::Session::mode
   RPC function [2].

2. You can pass a reference to a POD object as RPC argument.
   This is rarely used but you can find find an example in the
   Raspberry-Pi-specific platform-session interface, namely the
   setup_framebuffer RPC function [3].

[1] http://genode.org/documentation/genode-foundations-15-05.pdf
[2]
https://github.com/genodelabs/genode/blob/master/repos/os/include/framebuffer_session/framebuffer_session.h#L91
[3]
https://github.com/genodelabs/genode/blob/master/repos/os/include/spec/rpi/platform_session/platform_session.h#L39

Cheers
Norman

-- 
Dr.-Ing. Norman Feske
Genode Labs

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