[erlang-questions] Question about driver_select() and fd's out-of-band / exceptional events.

Nahuel Greco ngreco@REDACTED
Mon Mar 26 21:52:10 CEST 2007

Hi, from what I saw in the erl_driver/driver_entry manpages and
erl_driver.h file, you can use driver_select(...) from a linked-in
driver to pass a couple of file descriptors to the Erlang VM, and then
when these file descriptors have data to be read (DO_READ) or can be
written to (DO_WRITE), driver's ready_input() or ready_output() will
be called by the VM.

So, the driver is indirectly passing arguments to a select() call
somewhere in the Erlang VM. The problem is that I can't find how a
driver can give a file descriptor to the VM for _out of band_
information (the fourth argument to the select() call, "exceptfds")
with the purpose of be awaken as with ready_input or ready_output when
oob data becomes available on a fd.

Is this possible? I don't see any related field in driver_entry.

Nahuel Greco.

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