Am 10.10.2014 um 16:45 schrieb teclis High Elf:
From examples/libs/l4re/c++/shared_ds/ds_clnt.cc
line 49 : L4::CapL4::Irq irq = L4Re::Util::cap_alloc.allocL4::Irq();
It seems this template name L4::Cap and the function name L4Re::Util::cap_alloc are a bit misleading or only designate a sub-set of the objects functionality. In this line you are not just requesting permissions but getting a Unix style file handle that you then use to issue commands to the server on line 92:
irq->trigger();
Is my understanding correct?
No. Unfortunately not.
At line 49 you are opening L4 equivalent of a Unix style file handle for sending commands to a server and not requesting permissions or am I over simplifying.
There are two steps to accessing a kernel object (such as a software IRQ) in Fiasco. First you need to find a suitable spot in the process-local capability table to map the object to. Then, in a second step, you actually allocate the respective kernel object into this slot.
The line you are referring to only performs the first step (hence this is called cap_alloc.alloc()). The mapping from a real IRQ object to this capability is hidden in the svr->get_shared_buffer() call further down the line.
Bjoern