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A number of USB keyboards, using the Semitek firmware, are capable of handling arbitrary N-key rollover, but due to a buggy report descriptor, keys beyond the sixth cannot be detected by the generic HID driver. There are numerous hardware variants sold by several vendors, mostly using generic names like "GK61" for the 61-key version. These keyboards are sometimes known collectively as the "GK6X" series. The keyboard has three USB interfaces. Interface 0 uses the standard HID boot protocol, limited to eight modifier keys and six normal keys; interface 2 uses a custom report format that permits any number of keys. If more than six keys are pressed simultaneously, the first six are reported via interface 0 while subsequent keys are reported via interface 2. (Interface 1 uses a custom protocol for reprogramming the keyboard; this can be controlled through userspace tools and is not of concern for the present driver.) The report descriptor for interface 2, however, is incorrect (for report ID 0x04, the input field is marked as "array" rather than "variable".) The descriptor appears to be correct in other respects, so we simply replace the incorrect byte before parsing the descriptor. Signed-off-by: Benjamin Moody <bmoody@member.fsf.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
41 lines
1.0 KiB
C
41 lines
1.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* HID driver for Semitek keyboards
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*
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* Copyright (c) 2021 Benjamin Moody
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*/
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#include <linux/device.h>
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#include <linux/hid.h>
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#include <linux/module.h>
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#include "hid-ids.h"
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static __u8 *semitek_report_fixup(struct hid_device *hdev, __u8 *rdesc,
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unsigned int *rsize)
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{
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/* In the report descriptor for interface 2, fix the incorrect
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description of report ID 0x04 (the report contains a
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bitmask, not an array of keycodes.) */
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if (*rsize == 0xcb && rdesc[0x83] == 0x81 && rdesc[0x84] == 0x00) {
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hid_info(hdev, "fixing up Semitek report descriptor\n");
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rdesc[0x84] = 0x02;
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}
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return rdesc;
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}
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static const struct hid_device_id semitek_devices[] = {
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{ HID_USB_DEVICE(USB_VENDOR_ID_SEMITEK, USB_DEVICE_ID_SEMITEK_KEYBOARD) },
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{ }
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};
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MODULE_DEVICE_TABLE(hid, semitek_devices);
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static struct hid_driver semitek_driver = {
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.name = "semitek",
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.id_table = semitek_devices,
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.report_fixup = semitek_report_fixup,
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};
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module_hid_driver(semitek_driver);
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MODULE_LICENSE("GPL");
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