about weston

[Pekka Paalanen]

On Sun, 1 Apr 2012 21:37:10 +0200
Alberich de megres <alberich2k5 at gmail.com> wrote:

> Hi Guys,
> 
> I was trying to understand how weston rpc works, and more specifically
> how it asks for painting.
> Checking the source i saw more or less this call stack for sending a
> window_sync:
> 
> wl_display_sync
> |->wl_proxy_marshal
>    |->wl_closure_send
>        |->wl_connection_write
> 
> on the server side, the object demarshaling is done by vmarshal
> function, which some calls later invokes ffi_call
> 
> But I could not understand, the object is sended entirely? or just the
> function-parameters pointers to be invoked remotelly?

A protocol object has two parts in the code: some C struct containing a
struct wl_resource at minimum on the server side, and a proxy struct on
the client side.

A RPC only contains the protocol object id, opcode (request or event
id) and the arguments. The marshalling code you saw deals with all
the data types the wire can carry.

> if is this last case, how weston access the client memory space?

It doesn't. A client allocates its graphics buffers in a way, that you
can get a handle to it, pass the handle via the Wayland protocol, and
using the handle get access to the same graphics buffer in the server.

Unix shm is one supported buffer type, and the handle there is a file
descriptor.

http://cgit.freedesktop.org/wayland/wayland/tree/protocol/wayland.xml#n154


Thanks,
pq