usrp1: subdev spec tweaks and docs

3 files changed, 46 insertions, 11 deletions

diff --git a/host/docs/usrp1.rst b/host/docs/usrp1.rst
index ebc33cbfa..c960b928b 100644
--- a/host/docs/usrp1.rst
+++ b/host/docs/usrp1.rst
@@ -22,6 +22,41 @@ Change the USRP1's serial number
 TODO
 
 ------------------------------------------------------------------------
+Specifying the subdevice to use
+------------------------------------------------------------------------
+The USRP1 has multiple daughterboard slots, known as slot A and slot B.
+The subdevice specification can be used to select
+the daughterboard and subdevice for each channel.
+For daughterboards with one one subdevice,
+the subdevice name may be left blank for automatic selection.
+
+Ex: The subdev spec markup string to select a WBX on slot B.
+Notice the use of the blank subdevice name for automatic selection.
+
+::
+
+    B:
+
+    -- OR --
+
+    B:0
+
+Ex: The subdev spec markup string to select a BasicRX on slot B.
+Notice that the subdevice name is always specified in the 3 possible cases.
+
+::
+
+    B:AB
+
+    -- OR --
+
+    B:A
+
+    -- OR --
+
+    B:B
+
+------------------------------------------------------------------------
 OS Specific Notes
 ------------------------------------------------------------------------
 
diff --git a/host/include/uhd/usrp/subdev_spec.hpp b/host/include/uhd/usrp/subdev_spec.hpp
index 56aa0df20..2f32509b9 100644
--- a/host/include/uhd/usrp/subdev_spec.hpp
+++ b/host/include/uhd/usrp/subdev_spec.hpp
@@ -56,17 +56,8 @@ namespace uhd{ namespace usrp{
      *
      * The subdevice specification can be represented as a markup-string.
      * The markup-string is a whitespace separated list of dboard:subdev pairs.
-     * The "dboard:" part is optional on boards with only one daughterboard slot.
      * The first pair represents the subdevice for channel zero,
      * the second pair represents the subdevice for channel one, and so on.
-     *
-     * Examples:
-     * - Use subdevice AB on daughterboard A (USRP1): "A:AB"
-     * - Use subdevice A on daughterboard A for channel zero and subdevice A on daughterboard B for channel one (USRP1): "A:A B:A"
-     * - Use subdevice AB (USRP2): "AB" or ":AB"
-     *
-     * An empty subdevice specification can be used to automatically
-     * select the first subdevice on the first present daughterboard.
      */
     class UHD_API subdev_spec_t : public std::vector<subdev_spec_pair_t>{
     public:
diff --git a/host/lib/usrp/misc_utils.cpp b/host/lib/usrp/misc_utils.cpp
index a1664d810..5cfcdc8d3 100644
--- a/host/lib/usrp/misc_utils.cpp
+++ b/host/lib/usrp/misc_utils.cpp
@@ -164,13 +164,22 @@ static void verify_xx_subdev_spec(
             //empty db name means select dboard automatically
             if (pair.db_name.empty()){
                 if (dboard_names.size() != 1) throw std::runtime_error(
-                    "A daughterboard name must be provided for multi-slot boards: " + subdev_spec.to_string()
+                    "A daughterboard name must be provided for multi-slot motherboards: " + subdev_spec.to_string()
                 );
                 pair.db_name == dboard_names.front();
             }
             uhd::assert_has(dboard_names, pair.db_name, xx_type + " dboard name");
             wax::obj dboard = mboard[named_prop_t(dboard_prop, pair.db_name)];
-            uhd::assert_has(dboard[DBOARD_PROP_SUBDEV_NAMES].as<prop_names_t>(), pair.sd_name, xx_type + " subdev name");
+            prop_names_t subdev_names = dboard[DBOARD_PROP_SUBDEV_NAMES].as<prop_names_t>();
+
+            //empty sd name means select the subdev automatically
+            if (pair.sd_name.empty()){
+                if (subdev_names.size() != 1) throw std::runtime_error(
+                    "A subdevice name must be provided for multi-subdev daughterboards: " + subdev_spec.to_string()
+                );
+                pair.sd_name == subdev_names.front();
+            }
+            uhd::assert_has(subdev_names, pair.sd_name, xx_type + " subdev name");
         }
     }catch(const std::exception &e){
         throw std::runtime_error(str(boost::format(