build: prepare serial over Bluetooth, search for optional BlueZ lib

Adding Bluetooth communication is desirable for all sigrok supported
platforms. The BlueZ library is available on Linux which will receive
support first. Check for the BlueZ library's presence, determine a
HAVE_BLUETOOTH summary state, and extend the HAVE_SERIAL_COMM check.
Print version details for the external library.

This commit extends build support and version information, but does not
yet include the implementation of the serial transport primitives.

configure.ac

@@ -104,6 +104,8 @@ SR_ARG_OPT_PKG([libftdi], [LIBFTDI], , [libftdi1 >= 1.0])
 SR_ARG_OPT_PKG([libhidapi], [LIBHIDAPI], ,
 	[hidapi >= 0.8.0], [hidapi-hidraw >= 0.8.0], [hidapi-libusb >= 0.8.0])
 
+SR_ARG_OPT_PKG([libbluez], [LIBBLUEZ], , [bluez >= 4.0], [bluetooth >= 4.0])
+
 # FreeBSD comes with an "integrated" libusb-1.0-style USB API.
 # This means libusb-1.0 is always available; no need to check for it.
 # On Windows, require the latest version we can get our hands on,
@@ -133,7 +135,14 @@ SR_ARG_OPT_CHECK([libieee1284], [LIBIEEE1284],, [
 AS_IF([test "x$sr_have_libieee1284" = xyes],
 	[SR_PREPEND([SR_EXTRA_LIBS], [-lieee1284])])
 
-AS_IF([test "x$sr_have_libserialport" = xyes -o "x$sr_have_libhidapi" = xyes],
+# See if any of the (potentially platform specific) libs are available
+# which provide some means of Bluetooth communication.
+AS_IF([test "x$sr_have_libbluez" = xyes],
+	sr_have_bluetooth=yes, sr_have_bluetooth=no)
+AS_IF([test "x$sr_have_bluetooth" = xyes],
+	[AC_DEFINE([HAVE_BLUETOOTH], [1], [Specifies whether Bluetooth communication is supported.])])
+
+AS_IF([test "x$sr_have_libserialport" = xyes -o "x$sr_have_libhidapi" = xyes -o "x$sr_have_bluetooth" = xyes],
 	sr_have_serial_comm=yes, sr_have_serial_comm=no)
 AS_IF([test "x$sr_have_serial_comm" = xyes],
 	[AC_DEFINE([HAVE_SERIAL_COMM], [1], [Specifies whether serial communication is supported.])])
@@ -185,6 +194,15 @@ AM_CONDITIONAL([NEED_RPC], [test "x$sr_cv_have_rpc" = xyes])
 # Check for compiler support of 128 bit integers
 AC_CHECK_TYPES([__int128_t, __uint128_t], [], [], [])
 
+# Availability of bt_put_le16() depends on the bluez library version.
+AC_CACHE_CHECK([for bt_put_le16], [sr_cv_have_btputle16],
+	[AC_LINK_IFELSE([AC_LANG_PROGRAM(
+			[[#include <bluetooth/bluetooth.h>]],
+			[[bt_put_le16(0, (void *)0);]])],
+		[sr_cv_have_btputle16=yes], [sr_cv_have_btputle16=no])])
+AS_IF([test "x$sr_cv_have_btputle16" = xyes],
+	[AC_DEFINE([HAVE_BT_PUT_LE16], [1], [Specifies whether we have bt_put_le16().])])
+
 ########################
 ##  Hardware drivers  ##
 ########################
@@ -616,6 +634,8 @@ Enabled serial communication transports:
   - serial comm ................... $sr_have_serial_comm
   - libserialport ................. $sr_have_libserialport
   - hidapi ........................ $sr_have_libhidapi
+  - bluetooth ..................... $sr_have_bluetooth
+  - bluez ......................... $sr_have_libbluez
 
 Enabled SCPI backends:
  - TCP............................. yes

src/backend.c

@@ -169,6 +169,11 @@ SR_API GSList *sr_buildinfo_libs_get(void)
 	m = g_slist_append(m, g_strdup_printf("%s", CONF_LIBHIDAPI_VERSION));
 	l = g_slist_append(l, m);
 #endif
+#ifdef HAVE_LIBBLUEZ
+	m = g_slist_append(NULL, g_strdup("bluez"));
+	m = g_slist_append(m, g_strdup_printf("%s", CONF_LIBBLUEZ_VERSION));
+	l = g_slist_append(l, m);
+#endif
 #ifdef HAVE_LIBFTDI
 	m = g_slist_append(NULL, g_strdup("libftdi"));
 	m = g_slist_append(m, g_strdup_printf("%s", CONF_LIBFTDI_VERSION));