Add enablers for evdev event mapping

MCE assumes that certain events have strongly defined meaning, but on
some devices kernel is emitting events that do not match expectations
that mce has about them.

Make it possible to add configuration files that are used to translate
events kernel is emitting into what makes logical sense to mce.

[mce] Add enablers for evdev event mapping

evdev.c

@@ -352,3 +352,107 @@ int evdev_identify_device(int fd)
 
   return err;
 }
+
+static int rlookup(const char * const *lut, size_t cnt, const char *name)
+{
+  int val = -1;
+  for( size_t i = 0; i < cnt; ++i )
+  {
+    if( lut[i] && !strcmp(lut[i], name) )
+    {
+      val = (int)i;
+      break;
+    }
+  }
+  return val;
+}
+
+/* Internal helper functions for looking up event codes by type */
+static int syn_code(const char *ename)
+{
+  return rlookup(lut_syn, numof(lut_syn), ename);
+}
+
+static int key_code(const char *ename)
+{
+  return rlookup(lut_key, numof(lut_key), ename);
+}
+
+static int rel_code(const char *ename)
+{
+  return rlookup(lut_rel, numof(lut_rel), ename);
+}
+
+static int abs_code(const char *ename)
+{
+  return rlookup(lut_abs, numof(lut_abs), ename);
+}
+
+static int msc_code(const char *ename)
+{
+  return rlookup(lut_msc, numof(lut_msc), ename);
+}
+
+static int led_code(const char *ename)
+{
+  return rlookup(lut_led, numof(lut_led), ename);
+}
+
+static int rep_code(const char *ename)
+{
+  return rlookup(lut_rep, numof(lut_rep), ename);
+}
+
+static int snd_code(const char *ename)
+{
+  return rlookup(lut_snd, numof(lut_snd), ename);
+}
+
+static int sw_code(const char *ename)
+{
+  return rlookup(lut_sw, numof(lut_sw), ename);
+}
+
+static int ff_code(const char *ename)
+{
+  return rlookup(lut_ff, numof(lut_ff), ename);
+}
+
+static int pwr_code(const char *ename)
+{
+  (void)ename; // not used
+  return -1;
+}
+
+/** Lookup input event code by name
+ *
+ * @param etype input event type
+ * @param ename input event name
+ *
+ * @return input event code, or -1 in case of errors
+ */
+int evdev_lookup_event_code(int etype, const char *ename)
+{
+  typedef int (*lookup_fn)(const char *);
+
+  static const lookup_fn lut[] =
+  {
+    [EV_SYN] = syn_code,
+    [EV_KEY] = key_code,
+    [EV_REL] = rel_code,
+    [EV_ABS] = abs_code,
+    [EV_MSC] = msc_code,
+    [EV_SW]  = sw_code,
+    [EV_LED] = led_code,
+    [EV_SND] = snd_code,
+    [EV_REP] = rep_code,
+    [EV_FF]  = ff_code,
+    [EV_PWR] = pwr_code,
+  };
+
+  if( (size_t)etype < numof(lut) && lut[etype] )
+  {
+    return lut[etype](ename);
+  }
+  return -1;
+}

evdev.h

@@ -16,6 +16,8 @@ extern "C" {
 const char *evdev_get_event_code_name(int etype, int ecode);
 const char *evdev_get_event_type_name(int etype);
 
+int evdev_lookup_event_code(int etype, const char *ename);
+
 int evdev_open_device(const char *path);
 int evdev_identify_device(int fd);