LIBGPHOTO2_PORT(3) The gPhoto2 Reference (the man LIBGPHOTO2_PORT(3)

libgphoto2_port - cross-platform port access library

#include <gphoto2/gphoto2_port.h>

The libgphoto2_port library was written to provide libgphoto2(3) with a generic way of accessing ports. In this function, libgphoto2_port is the successor of the libgpio library.

Currently, libgphoto2_port supports serial (RS-232) and USB connections, the latter requiring libusb to be installed.

The autogenerated API docs will be added here in the future.

If set, defines the directory where the libgphoto2_port library looks for its I/O drivers (iolibs). You only need to set this on Windows systems and broken/test installations.
Set this to all to receive lots of debug information regarding library loading on ld based systems.
If set, defines the numeric debug level with which the libusb library will print messages. In order to get some debug output, set it to 1.

libgphoto2(3), The gPhoto2 Manual, [1]gphoto website, automatically generated API docs, [2]libusb website

The gPhoto2 Team.
Hans Ulrich Niedermann <gp@n-dimensional.de>. (man page)

1. gphoto website
http://www.gphoto.org/
2. libusb website
http://libusb.sourceforge.net/
08/16/2006