Add libx52_strerror API

lib/libx52/Makefile.am

@@ -4,8 +4,9 @@ lib_LTLIBRARIES = libx52.la
 
 # Core libx52 library
 # This library handles the USB communication between the host and the X52
-libx52_la_SOURCES = x52_control.c x52_core.c x52_date_time.c x52_mfd_led.c
-libx52_la_LDFLAGS = -version-info 2:0:0 -lusb-1.0
+libx52_la_SOURCES = x52_control.c x52_core.c x52_date_time.c x52_mfd_led.c \
+					x52_strerror.c
+libx52_la_LDFLAGS = -version-info 3:0:1 -lusb-1.0
 
 # Header files that need to be copied
 x52includedir = $(includedir)/x52pro

lib/libx52/libx52.h

@@ -460,6 +460,16 @@ int libx52_update(libx52_device *x52);
  */
 int libx52_vendor_command(libx52_device *x52, uint16_t index, uint16_t value);
 
+/**
+ * @brief Return a string representation of the error code
+ *
+ * @param[in]   error   Error code returned by libx52 function
+ *
+ * @returns Pointer to a NULL terminated string describing the error.
+ * Returned pointer must not be freed.
+ */
+char * libx52_strerror(libx52_error_code error);
+
 #ifdef __cplusplus
 }
 #endif

lib/libx52/x52_strerror.c

@@ -0,0 +1,81 @@
+/*
+ * Saitek X52 Pro MFD & LED driver
+ *
+ * Copyright (C) 2012-2017 Nirenjan Krishnan (nirenjan@nirenjan.org)
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License as
+ *  published by the Free Software Foundation, version 2.
+ *
+ */
+
+#include <stdio.h>
+
+#include "libx52.h"
+
+/** For future use in i18n */
+#define _(str)  str
+
+/* Error buffer used for building custom error strings */
+static char error_buffer[256];
+
+char * libx52_strerror(libx52_error_code error)
+{
+    switch (error) {
+    case LIBX52_SUCCESS:
+        return _("Success");
+
+    case LIBX52_ERROR_INIT_FAILURE:
+        return _("Initialization failure");
+
+    case LIBX52_ERROR_OUT_OF_MEMORY:
+        return _("Insufficient memory");
+
+    case LIBX52_ERROR_INVALID_PARAM:
+        return _("Invalid parameter");
+
+    case LIBX52_ERROR_NOT_SUPPORTED:
+        return _("Operation not supported");
+
+    case LIBX52_ERROR_TRY_AGAIN:
+        return _("Try again");
+
+    case LIBX52_ERROR_OUT_OF_RANGE:
+        return _("Input parameter out of range");
+
+    case LIBX52_ERROR_USB_FAILURE:
+        return _("USB transaction failure");
+
+    case LIBX52_ERROR_IO:
+        return _("USB input/output error");
+
+    case LIBX52_ERROR_PERM:
+        return _("Access denied");
+
+    case LIBX52_ERROR_NO_DEVICE:
+        return _("No such device");
+
+    case LIBX52_ERROR_NOT_FOUND:
+        return _("Entity not found");
+
+    case LIBX52_ERROR_BUSY:
+        return _("Resource busy");
+
+    case LIBX52_ERROR_TIMEOUT:
+        return _("Operation timeout");
+
+    case LIBX52_ERROR_OVERFLOW:
+        return _("Overflow");
+
+    case LIBX52_ERROR_PIPE:
+        return _("Pipe error");
+
+    case LIBX52_ERROR_INTERRUPTED:
+        return _("System call interrupted");
+
+    default:
+        snprintf(error_buffer, sizeof(error_buffer),
+                _("Unknown error %d"), error);
+        return error_buffer;
+    }
+}