lib: Purge all hard-coded references the share/uhd

- Add a new public API call get_pkg_data_path() which returns the
  location of the "share" data. On a Unix system, this will typically
  return "/usr/share/uhd" when doing a regular system install.
- Purge all references to this path in UHD, and use the new API call
  instead.
- Add --pkg-data-path as an option to uhd_config_info.

host/include/uhd/utils/paths.hpp

@@ -40,6 +40,16 @@ UHD_API std::string get_lib_path(void);
 // returning the parent directory of the library path.
 UHD_API std::string get_pkg_path(void);
 
+
+//! Get a string representing the system's package data directory ("share")
+//
+// This path is typically identical with get_pkg_path()/share/uhd, but can be
+// overridden with the UHD_PKG_DATA_PATH environment variable.
+//
+// This path is where UHD stores data files that are not part of the library
+// itself, such as images, RFNoC YAML files, and calibration data.
+UHD_API std::string get_pkg_data_path(void);
+
 //! Get a string representing the location of the calibration database
 UHD_API std::string get_cal_data_path(void);
 

host/lib/usrp/usrp2/usrp2_iface.cpp

@@ -16,6 +16,7 @@
 #include <uhd/utils/platform.hpp>
 #include <uhd/utils/safe_call.hpp>
 #include <uhd/utils/tasks.hpp>
+#include <uhdlib/utils/paths.hpp>
 #include <boost/asio.hpp> //used for htonl and ntohl
 #include <boost/assign/list_of.hpp>
 #include <boost/filesystem.hpp>

host/lib/usrp_clock/octoclock/octoclock_impl.cpp

@@ -19,6 +19,7 @@
 #include <uhd/utils/log.hpp>
 #include <uhd/utils/paths.hpp>
 #include <uhd/utils/static.hpp>
+#include <uhdlib/utils/paths.hpp>
 #include <stdint.h>
 #include <boost/asio.hpp>
 #include <boost/assign.hpp>

host/lib/utils/paths.cpp

@@ -272,6 +272,15 @@ std::string uhd::get_pkg_path(void)
     return get_env_var("UHD_PKG_PATH", pkg_path.string());
 }
 
+
+std::string uhd::get_pkg_data_path()
+{
+    return get_env_var("UHD_PKG_DATA_PATH",
+        (fs::path(uhd::get_pkg_path() / fs::path(uhd::build_info::pkg_data_dir()))
+                .string()));
+}
+
+
 std::string uhd::get_lib_path(void)
 {
     fs::path runtime_libfile_path = boost::dll::this_line_location();
@@ -302,8 +311,9 @@ std::vector<fs::path> uhd::get_module_paths(void)
         paths.push_back(str_path);
     }
 
-    paths.push_back(fs::path(uhd::get_lib_path()) / "uhd" / "modules");
-    paths.push_back(fs::path(uhd::get_pkg_path()) / "share" / "uhd" / "modules");
+    constexpr char module_dir[] = "modules";
+    paths.push_back(fs::path(uhd::get_lib_path()) / "uhd" / module_dir);
+    paths.push_back(fs::path(uhd::get_pkg_data_path()) / module_dir);
 
     return paths;
 }
@@ -319,7 +329,7 @@ std::vector<fs::path> uhd::get_module_d_paths(void)
 
     constexpr char module_d_dir[] = "modules.d";
     paths.push_back(fs::path(uhd::get_lib_path()) / "uhd" / module_d_dir);
-    paths.push_back(fs::path(uhd::get_pkg_path()) / "share" / "uhd" / module_d_dir);
+    paths.push_back(fs::path(uhd::get_pkg_data_path()) / module_d_dir);
 
     return paths;
 }
@@ -466,11 +476,14 @@ std::string uhd::get_images_dir(const std::string& search_paths)
     }
 
     /* Finally, check for the default UHD images installation paths */
-    for (auto& prefix : {uhd::get_pkg_path(), uhd::build_info::install_prefix()}) {
-        fs::path default_images_path = fs::path(prefix) / "share" / "uhd" / "images";
-        if (fs::is_directory(default_images_path)) {
-            return default_images_path.string();
-        }
+    const auto pkg_data_imgs_dir = fs::path(uhd::get_pkg_data_path()) / "images";
+    if (fs::is_directory(pkg_data_imgs_dir)) {
+        return pkg_data_imgs_dir.string();
+    }
+    const auto install_prefix_imgs_dir =
+        fs::path(uhd::build_info::install_prefix()) / "share" / "uhd" / "images";
+    if (fs::is_directory(install_prefix_imgs_dir)) {
+        return install_prefix_imgs_dir.string();
     }
 
     /* No luck. Return an empty string. */

host/tests/paths_test.cpp

@@ -45,6 +45,8 @@ BOOST_AUTO_TEST_CASE(test_get_paths)
     BOOST_CHECK(true);
     std::cout << "pkg_path: " << get_pkg_path() << std::endl;
     BOOST_CHECK(true);
+    std::cout << "pkg_data_path: " << get_pkg_data_path() << std::endl;
+    BOOST_CHECK(true);
     std::cout << "cal_path: " << get_cal_data_path() << std::endl;
     BOOST_CHECK(true);
 

host/utils/uhd_config_info.cpp

@@ -30,6 +30,7 @@ int UHD_SAFE_MAIN(int argc, char* argv[])
         ("dpdk-version",       "Print DPDK version")
         ("libusb-version",     "Print libusb version")
         ("pkg-path",           "Print pkg path")
+        ("pkg-data-path",      "Print package data path")
         ("lib-path",           "Print library path")
         ("images-dir",         "Print images dir")
         ("abi-version",        "Print ABI version string")
@@ -93,6 +94,9 @@ int UHD_SAFE_MAIN(int argc, char* argv[])
     if (vm.count("pkg-path") > 0 or print_all) {
         std::cout << "Package path: " << uhd::get_pkg_path() << std::endl;
     }
+    if (vm.count("pkg-data-path") > 0 or print_all) {
+        std::cout << "Package data path: " << uhd::get_pkg_data_path() << std::endl;
+    }
     if (vm.count("images-dir") > 0 or print_all) {
         std::cout << "Images directory: " << uhd::get_images_dir("") << std::endl;
     }

host/utils/uhd_images_downloader.py.in

@@ -63,8 +63,7 @@ except ImportError:
 _USERNAME_VARIABLE        = "UHD_IMAGES_USER"
 _PASSWORD_VARIABLE        = "UHD_IMAGES_PASSWORD"
 _DEFAULT_TARGET_REGEX     = "(fpga|fw|windrv)_default"
-_BASE_DIR_STRUCTURE_PARTS = ["share", "uhd", "images"]
-_DEFAULT_INSTALL_PATH     = os.path.join("@CMAKE_INSTALL_PREFIX@", *_BASE_DIR_STRUCTURE_PARTS)
+_DEFAULT_INSTALL_PATH     = os.path.join("@CONFIG_PATH@", "images")
 _DEFAULT_BASE_URL         = "https://files.ettus.com/binaries/cache/"
 _INVENTORY_FILENAME       = "inventory.json"
 _DEFAULT_BUFFER_SIZE      = 8192