+#ifdef CONFIG_INPUT
+
+/* Simple translation table for the SysRq keys */
+static const unsigned char sysrq_xlate[KEY_MAX + 1] =
+ "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
+ "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
+ "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
+ "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
+ "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
+ "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
+ "\r\000/"; /* 0x60 - 0x6f */
+
+static bool sysrq_down;
+static int sysrq_alt_use;
+static int sysrq_alt;
+
+static bool sysrq_filter(struct input_handle *handle, unsigned int type,
+ unsigned int code, int value)
+{
+ if (type != EV_KEY)
+ goto out;
+
+ switch (code) {
+
+ case KEY_LEFTALT:
+ case KEY_RIGHTALT:
+ if (value)
+ sysrq_alt = code;
+ else if (sysrq_down && code == sysrq_alt_use)
+ sysrq_down = false;
+ break;
+
+ case KEY_SYSRQ:
+ if (value == 1 && sysrq_alt) {
+ sysrq_down = true;
+ sysrq_alt_use = sysrq_alt;
+ }
+ break;
+
+ default:
+ if (sysrq_down && value && value != 2)
+ __handle_sysrq(sysrq_xlate[code], NULL, 1);
+ break;
+ }
+
+out:
+ return sysrq_down;
+}
+
+static int sysrq_connect(struct input_handler *handler,
+ struct input_dev *dev,
+ const struct input_device_id *id)
+{
+ struct input_handle *handle;
+ int error;
+
+ sysrq_down = false;
+ sysrq_alt = 0;
+
+ handle = kzalloc(sizeof(struct input_handle), GFP_KERNEL);
+ if (!handle)
+ return -ENOMEM;
+
+ handle->dev = dev;
+ handle->handler = handler;
+ handle->name = "sysrq";
+
+ error = input_register_handle(handle);
+ if (error) {
+ pr_err("Failed to register input sysrq handler, error %d\n",
+ error);
+ goto err_free;
+ }
+
+ error = input_open_device(handle);
+ if (error) {
+ pr_err("Failed to open input device, error %d\n", error);
+ goto err_unregister;
+ }
+
+ return 0;
+
+ err_unregister:
+ input_unregister_handle(handle);
+ err_free:
+ kfree(handle);
+ return error;
+}
+
+static void sysrq_disconnect(struct input_handle *handle)
+{
+ input_close_device(handle);
+ input_unregister_handle(handle);
+ kfree(handle);
+}
+
+/*
+ * We are matching on KEY_LEFTALT insteard of KEY_SYSRQ because not all
+ * keyboards have SysRq ikey predefined and so user may add it to keymap
+ * later, but we expect all such keyboards to have left alt.
+ */
+static const struct input_device_id sysrq_ids[] = {
+ {
+ .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+ INPUT_DEVICE_ID_MATCH_KEYBIT,
+ .evbit = { BIT_MASK(EV_KEY) },
+ .keybit = { BIT_MASK(KEY_LEFTALT) },
+ },
+ { },
+};
+
+static struct input_handler sysrq_handler = {
+ .filter = sysrq_filter,
+ .connect = sysrq_connect,
+ .disconnect = sysrq_disconnect,
+ .name = "sysrq",
+ .id_table = sysrq_ids,
+};
+
+static bool sysrq_handler_registered;
+
+static inline void sysrq_register_handler(void)
+{
+ int error;
+
+ error = input_register_handler(&sysrq_handler);
+ if (error)
+ pr_err("Failed to register input handler, error %d", error);
+ else
+ sysrq_handler_registered = true;
+}
+
+static inline void sysrq_unregister_handler(void)
+{
+ if (sysrq_handler_registered) {
+ input_unregister_handler(&sysrq_handler);
+ sysrq_handler_registered = false;
+ }
+}
+
+#else
+
+static inline void sysrq_register_handler(void)
+{
+}
+
+static inline void sysrq_unregister_handler(void)
+{
+}
+
+#endif /* CONFIG_INPUT */
+
+int sysrq_toggle_support(int enable_mask)
+{
+ bool was_enabled = sysrq_on();
+
+ sysrq_enabled = enable_mask;
+
+ if (was_enabled != sysrq_on()) {
+ if (sysrq_on())
+ sysrq_register_handler();
+ else
+ sysrq_unregister_handler();
+ }
+
+ return 0;
+}
+