platform/x86: asus-wmi: Filter buggy scan codes on ASUS Q500A

Some revisions of the ASUS Q500A series have a keyboard related
issue which is reproducible only after Windows with installed ASUS
tools is started.

In this case the Linux side will have a blocked keyboard or
report incorrect or incomplete hotkey events.

To make Linux work properly again, a complete power down
(unplug power supply and remove battery) is needed.

Linux/atkbd after a clean start will get the following code on VOLUME_UP
key: {0xe0, 0x30, 0xe0, 0xb0}. After Windows, the same key will generate
this codes: {0xe1, 0x23, 0xe0, 0x30, 0xe0, 0xb0}. As result atkdb will
be confused by buggy codes.

This patch is filtering this buggy code out.

https://bugzilla.kernel.org/show_bug.cgi?id=119391

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Cc: Alex Henrie <alexhenrie24@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Corentin Chary <corentin.chary@gmail.com>
Cc: acpi4asus-user@lists.sourceforge.net
Cc: platform-driver-x86@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

[dvhart: Add return after pr_warn to avoid false confirmation of filter]

Signed-off-by: Darren Hart <dvhart@linux.intel.com>

drivers/platform/x86/asus-nb-wmi.c

@@ -27,6 +27,7 @@
 #include <linux/input/sparse-keymap.h>
 #include <linux/fb.h>
 #include <linux/dmi.h>
+#include <linux/i8042.h>
 
 #include "asus-wmi.h"
 
@@ -55,10 +56,34 @@ MODULE_PARM_DESC(wapf, "WAPF value");
 
 static struct quirk_entry *quirks;
 
+static bool asus_q500a_i8042_filter(unsigned char data, unsigned char str,
+			      struct serio *port)
+{
+	static bool extended;
+	bool ret = false;
+
+	if (str & I8042_STR_AUXDATA)
+		return false;
+
+	if (unlikely(data == 0xe1)) {
+		extended = true;
+		ret = true;
+	} else if (unlikely(extended)) {
+		extended = false;
+		ret = true;
+	}
+
+	return ret;
+}
+
 static struct quirk_entry quirk_asus_unknown = {
 	.wapf = 0,
 };
 
+static struct quirk_entry quirk_asus_q500a = {
+	.i8042_filter = asus_q500a_i8042_filter,
+};
+
 /*
  * For those machines that need software to control bt/wifi status
  * and can't adjust brightness through ACPI interface
@@ -98,6 +123,15 @@ static int dmi_matched(const struct dmi_system_id *dmi)
 }
 
 static const struct dmi_system_id asus_quirks[] = {
+	{
+		.callback = dmi_matched,
+		.ident = "ASUSTeK COMPUTER INC. Q500A",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Q500A"),
+		},
+		.driver_data = &quirk_asus_q500a,
+	},
 	{
 		.callback = dmi_matched,
 		.ident = "ASUSTeK COMPUTER INC. U32U",
@@ -369,6 +403,8 @@ static const struct dmi_system_id asus_quirks[] = {
 
 static void asus_nb_wmi_quirks(struct asus_wmi_driver *driver)
 {
+	int ret;
+
 	quirks = &quirk_asus_unknown;
 	dmi_check_system(asus_quirks);
 
@@ -380,6 +416,15 @@ static void asus_nb_wmi_quirks(struct asus_wmi_driver *driver)
 		quirks->wapf = wapf;
 	else
 		wapf = quirks->wapf;
+
+	if (quirks->i8042_filter) {
+		ret = i8042_install_filter(quirks->i8042_filter);
+		if (ret) {
+			pr_warn("Unable to install key filter\n");
+			return;
+		}
+		pr_info("Using i8042 filter function for receiving events\n");
+	}
 }
 
 static const struct key_entry asus_nb_wmi_keymap[] = {

drivers/platform/x86/asus-wmi.h

@@ -28,6 +28,7 @@
 #define _ASUS_WMI_H_
 
 #include <linux/platform_device.h>
+#include <linux/i8042.h>
 
 #define ASUS_WMI_KEY_IGNORE (-1)
 #define ASUS_WMI_BRN_DOWN	0x20
@@ -52,6 +53,9 @@ struct quirk_entry {
 	 * and let the ACPI interrupt to send out the key event.
 	 */
 	int no_display_toggle;
+
+	bool (*i8042_filter)(unsigned char data, unsigned char str,
+			     struct serio *serio);
 };
 
 struct asus_wmi_driver {