uhd: Register API enhancements

- Added get_register_info function to get bitwidth and R/W access for a registers
- Better error reporting

2 files changed, 50 insertions, 11 deletions

diff --git a/host/include/uhd/usrp/multi_usrp.hpp b/host/include/uhd/usrp/multi_usrp.hpp
index 0c1e73895..80501e489 100644
--- a/host/include/uhd/usrp/multi_usrp.hpp
+++ b/host/include/uhd/usrp/multi_usrp.hpp
@@ -977,6 +977,26 @@ public:
     /*******************************************************************
      * Register IO methods
      ******************************************************************/
+    struct register_info_t {
+        size_t bitwidth;
+        bool readable;
+        bool writable;
+    };
+
+    /*!
+     * Enumerate the full paths of all low-level USRP register accessible to read/write
+     * \param mboard the motherboard index 0 to M-1
+     * \return a vector of register paths
+     */
+    virtual std::vector<std::string> enumerate_registers(const size_t mboard = 0) = 0;
+
+    /*!
+     * Get more information about a low-level device register
+     * \param path the full path to the register
+     * \param mboard the motherboard index 0 to M-1
+     * \return the info struct which contains the bitwidth and read-write access information
+     */
+    virtual register_info_t get_register_info(const std::string &path, const size_t mboard = 0) = 0;
 
     /*!
      * Write a low-level register field for a register in the USRP hardware
@@ -996,13 +1016,6 @@ public:
      */
     virtual boost::uint64_t read_register(const std::string &path, const boost::uint32_t field, const size_t mboard = 0) = 0;
 
-    /*!
-     * Enumerate the full paths of all low-level USRP register accessible to read/write
-     * \param mboard the motherboard index 0 to M-1
-     * \return a vector of register paths
-     */
-    virtual std::vector<std::string> enumerate_registers(const size_t mboard = 0) = 0;
-
     /*******************************************************************
      * Filter API methods
      ******************************************************************/
diff --git a/host/lib/usrp/multi_usrp.cpp b/host/lib/usrp/multi_usrp.cpp
index 285799674..f27d0ca03 100644
--- a/host/lib/usrp/multi_usrp.cpp
+++ b/host/lib/usrp/multi_usrp.cpp
@@ -1380,6 +1380,10 @@ public:
                 _tree->access<uhd::soft_regmap_accessor_t::sptr>(mb_root(mboard) / "registers").get();
             uhd::soft_register_base& reg = accessor->lookup(path);
 
+            if (not reg.is_writable()) {
+                throw uhd::runtime_error("multi_usrp::write_register - register not writable: " + path);
+            }
+
             switch (reg.get_bitwidth()) {
             case 16:
                 if (reg.is_readable())
@@ -1403,11 +1407,11 @@ public:
             break;
 
             default:
-                throw uhd::assertion_error("register has invalid bitwidth");
+                throw uhd::assertion_error("multi_usrp::write_register - register has invalid bitwidth");
             }
 
         } else {
-            throw uhd::not_implemented_error("register IO not supported for this device");
+            throw uhd::not_implemented_error("multi_usrp::write_register - register IO not supported for this device");
         }
     }
 
@@ -1419,6 +1423,10 @@ public:
                 _tree->access<uhd::soft_regmap_accessor_t::sptr>(mb_root(mboard) / "registers").get();
             uhd::soft_register_base& reg = accessor->lookup(path);
 
+            if (not reg.is_readable()) {
+                throw uhd::runtime_error("multi_usrp::read_register - register not readable: " + path);
+            }
+
             switch (reg.get_bitwidth()) {
             case 16:
                 if (reg.is_writable())
@@ -1442,10 +1450,10 @@ public:
             break;
 
             default:
-                throw uhd::assertion_error("register has invalid bitwidth: " + path);
+                throw uhd::assertion_error("multi_usrp::read_register - register has invalid bitwidth: " + path);
             }
         } else {
-            throw uhd::not_implemented_error("register IO not supported for this device");
+            throw uhd::not_implemented_error("multi_usrp::read_register - register IO not supported for this device");
         }
     }
 
@@ -1461,6 +1469,24 @@ public:
         }
     }
 
+    register_info_t get_register_info(const std::string &path, const size_t mboard = 0)
+    {
+        if (_tree->exists(mb_root(mboard) / "registers"))
+        {
+            uhd::soft_regmap_accessor_t::sptr accessor =
+                _tree->access<uhd::soft_regmap_accessor_t::sptr>(mb_root(mboard) / "registers").get();
+            uhd::soft_register_base& reg = accessor->lookup(path);
+
+            register_info_t info;
+            info.bitwidth = reg.get_bitwidth();
+            info.readable = reg.is_readable();
+            info.writable = reg.is_writable();
+            return info;
+        } else {
+            throw uhd::not_implemented_error("multi_usrp::read_register - register IO not supported for this device");
+        }
+    }
+
 private:
     device::sptr _dev;
     property_tree::sptr _tree;