Add feature check method to libx52

This change allows applications to query if the connected device
supports the requested feature. This is so that applications like
x52test can skip test routines that aren't supported, instead of bailing
out of the loop.

lib/libx52/libx52.h

@@ -197,6 +197,21 @@ typedef enum {
 
 } libx52_error_code;
 
+/**
+ * @brief Feature support for libx52
+ *
+ * Each flag is passed to \ref libx52_has_feature to determine if the connected
+ * device has the given feature. This list of features is only limited to those
+ * which differ between the supported devices.
+ *
+ * @ingroup libx52misc
+ */
+typedef enum {
+    /** Individual LED control */
+    LIBX52_FEATURE_LED,
+
+} libx52_feature;
+
 /**
  * @defgroup libx52init Library Initialization and Deinitialization
  * @{
@@ -500,6 +515,21 @@ int libx52_update(libx52_device *x52);
  */
 int libx52_vendor_command(libx52_device *x52, uint16_t index, uint16_t value);
 
+/**
+ * @brief Check if the device supports the given feature.
+ *
+ * This will check if the connected device supports the requested feature.
+ * It will return \ref LIBX52_SUCCESS if it does support it,
+ * \ref LIBX52_ERROR_NOT_SUPPORTED if it does not, and another \ref
+ * libx52_error_code on errors.
+ *
+ * @param[in]   x52     Pointer to the device
+ * @param[in]   feature Feature identifier (\ref libx52_feature)
+ *
+ * @returns \ref libx52_error_code indicating status
+ */
+int libx52_check_feature(libx52_device *x52, libx52_feature feature);
+
 /**
  * @brief Return a string representation of the error code
  *

lib/libx52/x52_core.c

@@ -132,3 +132,18 @@ void libx52_exit(libx52_device *dev)
     free(dev);
 }
 
+int libx52_check_feature(libx52_device *dev, libx52_feature feature)
+{
+    if (!dev) {
+        return LIBX52_ERROR_INVALID_PARAM;
+    }
+
+    switch (feature) {
+    case LIBX52_FEATURE_LED:
+        return tst_bit(&(dev->flags), X52_FLAG_IS_PRO) ?
+            LIBX52_SUCCESS :
+            LIBX52_ERROR_NOT_SUPPORTED;
+    }
+
+    return LIBX52_ERROR_INVALID_PARAM;
+}