[PATCH] hid: topre: Add driver fixing report descriptor

[Harry Stern]

The Topre REALFORCE R2 firmware incorrectly reports that interface
descriptor number 1, input report descriptor 2's events are array events
rather than variable events. That particular report descriptor is used
to report keypresses when there are more than 6 keys held at a time.
This bug prevents events from this interface from being registered
properly, so only 6 keypresses (from a different interface) can be
registered at once, rather than full n-key rollover.

This commit fixes the bug by setting the correct value in a report_fixup
function.

The original bug report can be found here:
Link: https://gitlab.freedesktop.org/libinput/libinput/-/issues/804

Thanks to Benjamin Tissoires for diagnosing the issue with the report
descriptor.

Signed-off-by: Harry Stern <harry@xxxxxxxxxxxxxx>
---
 drivers/hid/Kconfig     |  6 +++++
 drivers/hid/Makefile    |  1 +
 drivers/hid/hid-ids.h   |  3 +++
 drivers/hid/hid-topre.c | 49 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 59 insertions(+)
 create mode 100644 drivers/hid/hid-topre.c

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 6ce92830b..c4308d498 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -1141,6 +1141,12 @@ config HID_TOPSEED
 	Say Y if you have a TopSeed Cyberlink or BTC Emprex or Conceptronic
 	CLLRCMCE remote control.
 
+config HID_TOPRE
+	tristate "Topre REALFORCE keyboards"
+	depends on HID
+	help
+	  Say Y for N-key rollover support on Topre REALFORCE R2 108 key keyboards.
+
 config HID_THINGM
 	tristate "ThingM blink(1) USB RGB LED"
 	depends on HID
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index b0bef8098..bccaec0d7 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -123,6 +123,7 @@ obj-$(CONFIG_HID_GREENASIA)	+= hid-gaff.o
 obj-$(CONFIG_HID_THRUSTMASTER)	+= hid-tmff.o hid-thrustmaster.o
 obj-$(CONFIG_HID_TIVO)		+= hid-tivo.o
 obj-$(CONFIG_HID_TOPSEED)	+= hid-topseed.o
+obj-$(CONFIG_HID_TOPRE)	+= hid-topre.o
 obj-$(CONFIG_HID_TWINHAN)	+= hid-twinhan.o
 obj-$(CONFIG_HID_U2FZERO)	+= hid-u2fzero.o
 hid-uclogic-objs		:= hid-uclogic-core.o \
diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index f80d6193f..50bab12d9 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h
@@ -1231,6 +1231,9 @@
 #define USB_DEVICE_ID_TIVO_SLIDE	0x1201
 #define USB_DEVICE_ID_TIVO_SLIDE_PRO	0x1203
 
+#define USB_VENDOR_ID_TOPRE			0x0853
+#define USB_DEVICE_ID_TOPRE_REALFORCE_R2_108			0x0148
+
 #define USB_VENDOR_ID_TOPSEED		0x0766
 #define USB_DEVICE_ID_TOPSEED_CYBERLINK	0x0204
 
diff --git a/drivers/hid/hid-topre.c b/drivers/hid/hid-topre.c
new file mode 100644
index 000000000..88a91cdad
--- /dev/null
+++ b/drivers/hid/hid-topre.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  HID driver for Topre REALFORCE Keyboards
+ *
+ *  Copyright (c) 2022 Harry Stern <harry@xxxxxxxxxxxxxx>
+ *
+ *  Based on the hid-macally driver
+ */
+
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+MODULE_AUTHOR("Harry Stern <harry@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("REALFORCE R2 Keyboard driver");
+MODULE_LICENSE("GPL");
+
+/*
+ * Fix the REALFORCE R2's non-boot interface's report descriptor to match the
+ * events it's actually sending. It claims to send array events but is instead
+ * sending variable events.
+ */
+static __u8 *topre_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+				 unsigned int *rsize)
+{
+	if (*rsize >= 119 && rdesc[69] == 0x29 && rdesc[70] == 0xe7 &&
+						 rdesc[71] == 0x81 && rdesc[72] == 0x00) {
+		hid_info(hdev,
+			"fixing up Topre REALFORCE keyboard report descriptor\n");
+		rdesc[72] = 0x02;
+	}
+	return rdesc;
+}
+
+static const struct hid_device_id topre_id_table[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_TOPRE,
+			 USB_DEVICE_ID_TOPRE_REALFORCE_R2_108) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, topre_id_table);
+
+static struct hid_driver topre_driver = {
+	.name			= "topre",
+	.id_table		= topre_id_table,
+	.report_fixup		= topre_report_fixup,
+};
+
+module_hid_driver(topre_driver);
-- 
2.37.3