+ dnl not using libusb1 (for now); see if legacy version is found.
+ dnl it might be installed under the name either 'libusb' or
+ dnl 'libusb-legacy', or just available via the
+ dnl user's shell environment
+
+ dnl see if the pkgconfig module 'libusb' is available
+ PKG_CHECK_MODULES(USB, libusb, [
+ libusbok=yes
+ LIBUSB_PKG_CONFIG_NAME='libusb'
+ ], [libusbok=no])
+ dnl PKG_CHECK_MODULES does not work correctly when embedded
+ if test $libusbok = no; then
+ dnl if not, see if the pkgconfig module 'libusb-legacy' is available
+ PKG_CHECK_MODULES(USB, [libusb-legacy], [
+ libusbok=yes
+ LIBUSB_PKG_CONFIG_NAME='libusb-legacy'
+ ], [libusbok=no])
+ fi
+ dnl set variables for further testing
+ usb_header='usb.h'
+ usb_lib_func='usb_bulk_write'
+ usb_lib_name='usb'
+ fi
+ AC_SUBST(LIBUSB_PKG_CONFIG_NAME)
+ if test x$1 != xyes || test $have_libusb1 = yes; then
+ dnl Either (1) libusb1 was specified and found; or
+ dnl (2) libusb1 was not specified. Restart checking.
+ libusbok=yes
+
+ dnl Verify that $usb_header is a valid header, and if so,
+ dnl then verify that $usb_lib_func can be found in the
+ dnl library $usb_lib_name.
+
+ dnl If PKGCONFIG found variable USB_INCLUDEDIR, and it is
+ dnl not empty, use it for checking for $usb_header.
+ dnl Otherwise, maybe the user's shell environment is already
+ dnl configured to find this header.
+
+ AC_LANG_PUSH(C)
+ save_CPPFLAGS="$CPPFLAGS"
+ if test x$USB_INCLUDEDIR != x; then
+ USB_INCLUDES="-I$USB_INCLUDEDIR"
+ CPPFLAGS="$CPPFLAGS $USB_INCLUDES"
+ AC_SUBST(USB_INCLUDES)
+ fi
+ AC_CHECK_HEADERS([$usb_header], [], [libusbok=no])
+ CPPFLAGS="$save_CPPFLAGS"
+ AC_LANG_POP(C)
+
+ if test $libusbok = no; then
+ AC_MSG_RESULT([USRP requires libusb header '$usb_header' which was not found or was not usable. See http://www.libusb.org])
+ else
+
+ dnl found the header; now make sure the library is OK
+ dnl On Darwin, need to include the IOKit library.
+