Input: i8042 - allow installing platform filters for incoming data

Some hardware (such as Dell laptops) signal a variety of events through
the i8042 controller, even if these don't map to keyboard events. Add
support for drivers to filter the i8042 event stream in order to respond
to these events and (if appropriate) block them from entering the input
stream.
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/serio/i8042.c

@@ -126,6 +126,8 @@ static unsigned char i8042_suppress_kbd_ack;
 static struct platform_device *i8042_platform_device;
 
 static irqreturn_t i8042_interrupt(int irq, void *dev_id);
+static bool (*i8042_platform_filter)(unsigned char data, unsigned char str,
+				     struct serio *serio);
 
 void i8042_lock_chip(void)
 {
@@ -139,6 +141,48 @@ void i8042_unlock_chip(void)
 }
 EXPORT_SYMBOL(i8042_unlock_chip);
 
+int i8042_install_filter(bool (*filter)(unsigned char data, unsigned char str,
+					struct serio *serio))
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&i8042_lock, flags);
+
+	if (i8042_platform_filter) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	i8042_platform_filter = filter;
+
+out:
+	spin_unlock_irqrestore(&i8042_lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(i8042_install_filter);
+
+int i8042_remove_filter(bool (*filter)(unsigned char data, unsigned char str,
+				       struct serio *port))
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&i8042_lock, flags);
+
+	if (i8042_platform_filter != filter) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	i8042_platform_filter = NULL;
+
+out:
+	spin_unlock_irqrestore(&i8042_lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(i8042_remove_filter);
+
 /*
  * The i8042_wait_read() and i8042_wait_write functions wait for the i8042 to
  * be ready for reading values from it / writing values to it.
@@ -373,7 +417,8 @@ static void i8042_stop(struct serio *serio)
  * It is called from i8042_interrupt and thus is running with interrupts
  * off and i8042_lock held.
  */
-static bool i8042_filter(unsigned char data, unsigned char str)
+static bool i8042_filter(unsigned char data, unsigned char str,
+			 struct serio *serio)
 {
 	if (unlikely(i8042_suppress_kbd_ack)) {
 		if ((~str & I8042_STR_AUXDATA) &&
@@ -384,6 +429,11 @@ static bool i8042_filter(unsigned char data, unsigned char str)
 		}
 	}
 
+	if (i8042_platform_filter && i8042_platform_filter(data, str, serio)) {
+		dbg("Filtered out by platfrom filter\n");
+		return true;
+	}
+
 	return false;
 }
 
@@ -396,6 +446,7 @@ static bool i8042_filter(unsigned char data, unsigned char str)
 static irqreturn_t i8042_interrupt(int irq, void *dev_id)
 {
 	struct i8042_port *port;
+	struct serio *serio;
 	unsigned long flags;
 	unsigned char str, data;
 	unsigned int dfl;
@@ -462,18 +513,19 @@ static irqreturn_t i8042_interrupt(int irq, void *dev_id)
 	}
 
 	port = &i8042_ports[port_no];
+	serio = port->exists ? port->serio : NULL;
 
 	dbg("%02x <- i8042 (interrupt, %d, %d%s%s)",
 	    data, port_no, irq,
 	    dfl & SERIO_PARITY ? ", bad parity" : "",
 	    dfl & SERIO_TIMEOUT ? ", timeout" : "");
 
-	filtered = i8042_filter(data, str);
+	filtered = i8042_filter(data, str, serio);
 
 	spin_unlock_irqrestore(&i8042_lock, flags);
 
 	if (likely(port->exists && !filtered))
-		serio_interrupt(port->serio, data, dfl);
+		serio_interrupt(serio, data, dfl);
 
  out:
 	return IRQ_RETVAL(ret);

include/linux/i8042.h

@@ -39,6 +39,10 @@ void i8042_lock_chip(void);
 void i8042_unlock_chip(void);
 int i8042_command(unsigned char *param, int command);
 bool i8042_check_port_owner(const struct serio *);
+int i8042_install_filter(bool (*filter)(unsigned char data, unsigned char str,
+					struct serio *serio));
+int i8042_remove_filter(bool (*filter)(unsigned char data, unsigned char str,
+				       struct serio *serio));
 
 #else
 
@@ -52,7 +56,7 @@ void i8042_unlock_chip(void)
 
 int i8042_command(unsigned char *param, int command)
 {
-	return -ENOSYS;
+	return -ENODEV;
 }
 
 bool i8042_check_port_owner(const struct serio *serio)
@@ -60,6 +64,18 @@ bool i8042_check_port_owner(const struct serio *serio)
 	return false;
 }
 
+int i8042_install_filter(bool (*filter)(unsigned char data, unsigned char str,
+					struct serio *serio))
+{
+	return -ENODEV;
+}
+
+int i8042_remove_filter(bool (*filter)(unsigned char data, unsigned char str,
+				       struct serio *serio))
+{
+	return -ENODEV;
+}
+
 #endif
 
 #endif