HID: redragon: Fix modifier keys for Redragon Asura Keyboard

This adds a new driver for the Redragon Asura keyboard. The Asura
keyboard contains an error in the HID descriptor which causes all
modifier keys to be mapped to left shift. Additionally, we suppress
the creation of a second, not working, keyboard device.

Signed-off-by: Robert Munteanu <rombert@apache.org>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 86 insertions, 0 deletions

diff --git a/drivers/hid/hid-redragon.c b/drivers/hid/hid-redragon.c
new file mode 100644
index 000000000000..daf59578bf93
--- /dev/null
+++ b/drivers/hid/hid-redragon.c
@@ -0,0 +1,86 @@
+/*
+ *  HID driver for Redragon keyboards
+ *
+ *  Copyright (c) 2017 Robert Munteanu
+ *  SPDX-License-Identifier: GPL-2.0+
+ */
+
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+
+/*
+ * The Redragon Asura keyboard sends an incorrect HID descriptor.
+ * At byte 100 it contains
+ *
+ *   0x81, 0x00
+ *
+ * which is Input (Data, Arr, Abs), but it should be
+ *
+ *   0x81, 0x02
+ *
+ * which is Input (Data, Var, Abs), which is consistent with the way
+ * key codes are generated.
+ */
+
+static __u8 *redragon_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+	unsigned int *rsize)
+{
+	if (*rsize >= 102 && rdesc[100] == 0x81 && rdesc[101] == 0x00) {
+		dev_info(&hdev->dev, "Fixing Redragon ASURA report descriptor.\n");
+		rdesc[101] = 0x02;
+	}
+
+	return rdesc;
+}
+
+static int redragon_probe(struct hid_device *dev,
+	const struct hid_device_id *id)
+{
+	int ret;
+
+	ret = hid_parse(dev);
+	if (ret) {
+		hid_err(dev, "parse failed\n");
+		return ret;
+	}
+
+	/* do not register unused input device */
+	if (dev->maxapplication == 1)
+		return 0;
+
+	ret = hid_hw_start(dev, HID_CONNECT_DEFAULT);
+	if (ret) {
+		hid_err(dev, "hw start failed\n");
+		return ret;
+	}
+
+	return 0;
+}
+static const struct hid_device_id redragon_devices[] = {
+	{HID_USB_DEVICE(USB_VENDOR_ID_JESS, USB_DEVICE_ID_REDRAGON_ASURA)},
+	{}
+};
+
+MODULE_DEVICE_TABLE(hid, redragon_devices);
+
+static struct hid_driver redragon_driver = {
+	.name = "redragon",
+	.id_table = redragon_devices,
+	.report_fixup = redragon_report_fixup,
+	.probe = redragon_probe
+};
+
+module_hid_driver(redragon_driver);
+
+MODULE_LICENSE("GPL");