+#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
+static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
+static unsigned int sysrq_reset_seq_len;
+static unsigned int sysrq_reset_seq_version = 1;
+
+static void sysrq_parse_reset_sequence(struct sysrq_state *state)
+{
+ int i;
+ unsigned short key;
+
+ state->reset_seq_cnt = 0;
+
+ for (i = 0; i < sysrq_reset_seq_len; i++) {
+ key = sysrq_reset_seq[i];
+
+ if (key == KEY_RESERVED || key > KEY_MAX)
+ break;
+
+ __set_bit(key, state->reset_keybit);
+ state->reset_seq_len++;
+
+ if (test_bit(key, state->key_down))
+ state->reset_seq_cnt++;
+ }
+
+ /* Disable reset until old keys are not released */
+ state->reset_canceled = state->reset_seq_cnt != 0;
+
+ state->reset_seq_version = sysrq_reset_seq_version;
+}
+
+static bool sysrq_detect_reset_sequence(struct sysrq_state *state,
+ unsigned int code, int value)
+{
+ if (!test_bit(code, state->reset_keybit)) {
+ /*
+ * Pressing any key _not_ in reset sequence cancels
+ * the reset sequence.
+ */
+ if (value && state->reset_seq_cnt)
+ state->reset_canceled = true;
+ } else if (value == 0) {
+ /* key release */
+ if (--state->reset_seq_cnt == 0)
+ state->reset_canceled = false;
+ } else if (value == 1) {
+ /* key press, not autorepeat */
+ if (++state->reset_seq_cnt == state->reset_seq_len &&
+ !state->reset_canceled) {
+ return true;
+ }
+ }
+
+ return false;
+}
+