NetBSD: Initial UHID native backend implementation (#612)

CMakeLists.txt

@@ -42,6 +42,9 @@ elseif(NOT WIN32)
         option(HIDAPI_WITH_HIDRAW "Build HIDRAW-based implementation of HIDAPI" ON)
         option(HIDAPI_WITH_LIBUSB "Build LIBUSB-based implementation of HIDAPI" ON)
     endif()
+    if(CMAKE_SYSTEM_NAME MATCHES "NetBSD")
+        option(HIDAPI_WITH_NETBSD "Build NetBSD/UHID implementation of HIDAPI" ON)
+    endif()
 endif()
 
 option(BUILD_SHARED_LIBS "Build shared version of the libraries, otherwise build statically" ON)

netbsd/CMakeLists.txt

@@ -0,0 +1,35 @@
+cmake_minimum_required(VERSION 3.6.3 FATAL_ERROR)
+
+add_library(hidapi_netbsd
+    ${HIDAPI_PUBLIC_HEADERS}
+    hid.c
+)
+target_link_libraries(hidapi_netbsd PUBLIC hidapi_include)
+
+find_package(Threads REQUIRED)
+
+target_link_libraries(hidapi_netbsd PRIVATE Threads::Threads)
+
+set_target_properties(hidapi_netbsd
+    PROPERTIES
+        EXPORT_NAME "netbsd"
+        OUTPUT_NAME "hidapi-netbsd"
+        VERSION ${PROJECT_VERSION}
+        SOVERSION ${PROJECT_VERSION_MAJOR}
+        PUBLIC_HEADER "${HIDAPI_PUBLIC_HEADERS}"
+)
+
+# compatibility with find_package()
+add_library(hidapi::netbsd ALIAS hidapi_netbsd)
+# compatibility with raw library link
+add_library(hidapi-netbsd ALIAS hidapi_netbsd)
+
+if(HIDAPI_INSTALL_TARGETS)
+    install(TARGETS hidapi_netbsd EXPORT hidapi
+        LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+        ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+        PUBLIC_HEADER DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/hidapi"
+    )
+endif()
+
+hidapi_configure_pc("${PROJECT_ROOT}/pc/hidapi-netbsd.pc.in")

netbsd/README.md

@@ -0,0 +1,29 @@
+Implementation Notes
+--------------------
+NetBSD maps every `uhidev` device to one or more `uhid`
+devices. Each `uhid` device only supports one report ID.
+The parent device `uhidev` creates one `uhid` device per
+report ID found in the hardware's report descriptor.
+
+In the event there are no report ID(s) found within the
+report descriptor, only one `uhid` device with a report ID
+of `0` is created.
+
+In order to remain compatible with existing `hidapi` APIs,
+all the `uhid` devices created by the parent `uhidev` device
+must be opened under the same `hid_device` instance to ensure
+that we can route reports to their appropriate `uhid` device.
+
+Internally the `uhid` driver will insert the report ID as
+needed so we must also omit the report ID in any situation
+where the `hidapi` API expects it to be included in the
+report data stream.
+
+Given the design of `uhid`, it must be augmented with extra
+platform specific APIs to ensure that the exact relationship
+between `uhidev` devices and `uhid` devices can be determined.
+
+The NetBSD implementation does this via the `drvctl` kernel
+driver. At present there is no known way to do this on OpenBSD
+for a `uhid` implementation to be at the same level as the
+NetBSD one.