+EXPORT_SYMBOL(ps2_sendbyte);
+
+/*
+ * ps2_drain() waits for device to transmit requested number of bytes
+ * and discards them.
+ */
+
+void ps2_drain(struct ps2dev *ps2dev, int maxbytes, int timeout)
+{
+ if (maxbytes > sizeof(ps2dev->cmdbuf)) {
+ WARN_ON(1);
+ maxbytes = sizeof(ps2dev->cmdbuf);
+ }
+
+ mutex_lock(&ps2dev->cmd_mutex);
+
+ serio_pause_rx(ps2dev->serio);
+ ps2dev->flags = PS2_FLAG_CMD;
+ ps2dev->cmdcnt = maxbytes;
+ serio_continue_rx(ps2dev->serio);
+
+ wait_event_timeout(ps2dev->wait,
+ !(ps2dev->flags & PS2_FLAG_CMD),
+ msecs_to_jiffies(timeout));
+ mutex_unlock(&ps2dev->cmd_mutex);
+}
+EXPORT_SYMBOL(ps2_drain);
+
+/*
+ * ps2_is_keyboard_id() checks received ID byte against the list of
+ * known keyboard IDs.
+ */
+
+int ps2_is_keyboard_id(char id_byte)
+{
+ const static char keyboard_ids[] = {
+ 0xab, /* Regular keyboards */
+ 0xac, /* NCD Sun keyboard */
+ 0x2b, /* Trust keyboard, translated */
+ 0x5d, /* Trust keyboard */
+ 0x60, /* NMB SGI keyboard, translated */
+ 0x47, /* NMB SGI keyboard */
+ };
+
+ return memchr(keyboard_ids, id_byte, sizeof(keyboard_ids)) != NULL;
+}
+EXPORT_SYMBOL(ps2_is_keyboard_id);
+
+/*
+ * ps2_adjust_timeout() is called after receiving 1st byte of command
+ * response and tries to reduce remaining timeout to speed up command
+ * completion.
+ */
+
+static int ps2_adjust_timeout(struct ps2dev *ps2dev, int command, int timeout)
+{
+ switch (command) {
+ case PS2_CMD_RESET_BAT:
+ /*
+ * Device has sent the first response byte after
+ * reset command, reset is thus done, so we can
+ * shorten the timeout.
+ * The next byte will come soon (keyboard) or not
+ * at all (mouse).
+ */
+ if (timeout > msecs_to_jiffies(100))
+ timeout = msecs_to_jiffies(100);
+ break;
+
+ case PS2_CMD_GETID:
+ /*
+ * Microsoft Natural Elite keyboard responds to
+ * the GET ID command as it were a mouse, with
+ * a single byte. Fail the command so atkbd will
+ * use alternative probe to detect it.
+ */
+ if (ps2dev->cmdbuf[1] == 0xaa) {
+ serio_pause_rx(ps2dev->serio);
+ ps2dev->flags = 0;
+ serio_continue_rx(ps2dev->serio);
+ timeout = 0;
+ }
+
+ /*
+ * If device behind the port is not a keyboard there
+ * won't be 2nd byte of ID response.
+ */
+ if (!ps2_is_keyboard_id(ps2dev->cmdbuf[1])) {
+ serio_pause_rx(ps2dev->serio);
+ ps2dev->flags = ps2dev->cmdcnt = 0;
+ serio_continue_rx(ps2dev->serio);
+ timeout = 0;
+ }
+ break;
+
+ default:
+ break;
+ }
+
+ return timeout;
+}