[PATCH] Handle spurious backslash key repeats on some keyboards

[Fredrik Hallenberg <megahallon@gmail.com>]

Here is my attempt on a fix for bug 70181, please review it. It is
tested on my nordic Corsair K70, if this solution is deemed acceptable
I can ask some people with other problematic keyboards to test it.

Signed-off-by: Fredrik Hallenberg <megahallon@gmail.com>
---
 drivers/hid/hid-input.c | 14 ++++++++++++++
 include/linux/hid.h     |  1 +
 2 files changed, 15 insertions(+)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 2619f7f..56429c0 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1085,6 +1085,20 @@ void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct
 		return;
 	}
 
+	/*
+	 * Some keyboards will report both HID keys 0x31 (\ and |) and
+	 * 0x32 (Non-US # and ~) which are both mapped to
+	 * KEY_BACKSLASH. This will cause spurious events causing
+	 * repeated backslash key presses. Handle this by tracking the
+	 * active HID code and ignoring the other one.
+	 */
+	if (usage->type == EV_KEY && usage->code == KEY_BACKSLASH) {
+		if (value)
+			field->hidinput->backslash_usage = usage->hid;
+		else if (field->hidinput->backslash_usage != usage->hid)
+			return;
+	}
+
 	/* report the usage code as scancode if the key status has changed */
 	if (usage->type == EV_KEY && !!test_bit(usage->code, input->key) != value)
 		input_event(input, EV_MSC, MSC_SCAN, usage->hid);
diff --git a/include/linux/hid.h b/include/linux/hid.h
index f53c4a9..1c59f8f 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -448,6 +448,7 @@ struct hid_input {
 	struct list_head list;
 	struct hid_report *report;
 	struct input_dev *input;
+	unsigned backslash_usage;
 };
 
 enum hid_type {
-- 
2.1.0.rc1