Input: add ps2_drain() to libps2 to allow reading and discarding

       given number of bytes from device. Change ps2_command to
       allow using 0 as command ID and actually pass it to the
       device instead of working as a drain.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/mouse/alps.c

@@ -270,7 +270,6 @@ static struct alps_model_info *alps_get_model(struct psmouse *psmouse, int *vers
 static int alps_passthrough_mode(struct psmouse *psmouse, int enable)
 {
 	struct ps2dev *ps2dev = &psmouse->ps2dev;
-	unsigned char param[3];
 	int cmd = enable ? PSMOUSE_CMD_SETSCALE21 : PSMOUSE_CMD_SETSCALE11;
 
 	if (ps2_command(ps2dev, NULL, cmd) ||
@@ -280,7 +279,7 @@ static int alps_passthrough_mode(struct psmouse *psmouse, int enable)
 		return -1;
 
 	/* we may get 3 more bytes, just ignore them */
-	ps2_command(ps2dev, param, 0x0300);
+	ps2_drain(ps2dev, 3, 100);
 
 	return 0;
 }

drivers/input/serio/libps2.c

@@ -29,6 +29,7 @@ MODULE_LICENSE("GPL");
 
 EXPORT_SYMBOL(ps2_init);
 EXPORT_SYMBOL(ps2_sendbyte);
+EXPORT_SYMBOL(ps2_drain);
 EXPORT_SYMBOL(ps2_command);
 EXPORT_SYMBOL(ps2_schedule_command);
 EXPORT_SYMBOL(ps2_handle_ack);
@@ -45,11 +46,11 @@ struct ps2work {
 
 
 /*
- * ps2_sendbyte() sends a byte to the mouse, and waits for acknowledge.
- * It doesn't handle retransmission, though it could - because when there would
- * be need for retransmissions, the mouse has to be replaced anyway.
+ * ps2_sendbyte() sends a byte to the device and waits for acknowledge.
+ * It doesn't handle retransmission, though it could - because if there
+ * is a need for retransmissions device has to be replaced anyway.
  *
- * ps2_sendbyte() can only be called from a process context
+ * ps2_sendbyte() can only be called from a process context.
  */
 
 int ps2_sendbyte(struct ps2dev *ps2dev, unsigned char byte, int timeout)
@@ -71,6 +72,31 @@ int ps2_sendbyte(struct ps2dev *ps2dev, unsigned char byte, int timeout)
 	return -ps2dev->nak;
 }
 
+/*
+ * 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);
+	}
+
+	down(&ps2dev->cmd_sem);
+
+	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));
+	up(&ps2dev->cmd_sem);
+}
+
 /*
  * ps2_command() sends a command and its parameters to the mouse,
  * then waits for the response and puts it in the param array.
@@ -86,6 +112,11 @@ int ps2_command(struct ps2dev *ps2dev, unsigned char *param, int command)
 	int rc = -1;
 	int i;
 
+	if (receive > sizeof(ps2dev->cmdbuf)) {
+		WARN_ON(1);
+		return -1;
+	}
+
 	down(&ps2dev->cmd_sem);
 
 	serio_pause_rx(ps2dev->serio);
@@ -101,7 +132,6 @@ int ps2_command(struct ps2dev *ps2dev, unsigned char *param, int command)
 	 * ACKing the reset command, and so it can take a long
 	 * time before the ACK arrrives.
 	 */
-	if (command & 0xff)
 	if (ps2_sendbyte(ps2dev, command & 0xff,
 			 command == PS2_CMD_RESET_BAT ? 1000 : 200))
 		goto out;

include/linux/libps2.h

@@ -41,6 +41,7 @@ struct ps2dev {
 
 void ps2_init(struct ps2dev *ps2dev, struct serio *serio);
 int ps2_sendbyte(struct ps2dev *ps2dev, unsigned char byte, int timeout);
+void ps2_drain(struct ps2dev *ps2dev, int maxbytes, int timeout);
 int ps2_command(struct ps2dev *ps2dev, unsigned char *param, int command);
 int ps2_schedule_command(struct ps2dev *ps2dev, unsigned char *param, int command);
 int ps2_handle_ack(struct ps2dev *ps2dev, unsigned char data);