bpf: Add fix for Trust Philips SPK6327 (145f:024b) modifier keys

The Trust Philips SPK6327 keyboard (USB ID 145f:024b) has a broken HID
descriptor on interface 1. Byte 101 is 0x00 (Input Array) but should be
0x02 (Input Variable), causing LCtrl, LAlt, Super, RAlt, RCtrl and
RShift to all report as LShift on Linux.

This BPF fix patches byte 101 at runtime fixing all affected modifier
keys.

Link: https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/234
Signed-off-by: muhammed Rishal <muhammedrishal7777777@gmail.com>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

Author: Limexien

drivers/hid/bpf/progs/Trust__Philips-SPK6327.bpf.c

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Fix for Trust Philips SPK6327 (145f:024b)
+ * Modifier keys report as Array (0x00) instead of Variable (0x02)
+ * causing LCtrl, LAlt, Super etc. to all act as LShift
+ */
+#include "vmlinux.h"
+#include "hid_bpf.h"
+#include "hid_bpf_helpers.h"
+#include <bpf/bpf_tracing.h>
+
+#define VID_TRUST 0x145F
+#define PID_SPK6327 0x024B
+
+HID_BPF_CONFIG(
+	HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_TRUST, PID_SPK6327)
+);
+
+SEC(HID_BPF_RDESC_FIXUP)
+int BPF_PROG(hid_fix_rdesc, struct hid_bpf_ctx *hctx)
+{
+	__u8 *data = hid_bpf_get_data(hctx, 0, 4096);
+
+	if (!data)
+		return 0;
+
+	/* Fix modifier keys: Input Array (0x00) -> Input Variable (0x02) */
+	if (data[101] == 0x00)
+		data[101] = 0x02;
+
+	return 0;
+}
+
+HID_BPF_OPS(trust_spk6327) = {
+	.hid_rdesc_fixup = (void *)hid_fix_rdesc,
+};
+
+SEC("syscall")
+int probe(struct hid_bpf_probe_args *ctx)
+{
+	/* Only apply to interface 1 (169 bytes) not interface 0 (62 bytes) */
+	if (ctx->rdesc_size == 169)
+		ctx->retval = 0;
+	else
+		ctx->retval = -EINVAL;
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";