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// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2025 Benjamin Tissoires
*/
#include "vmlinux.h"
#include "hid_bpf.h"
#include "hid_bpf_helpers.h"
#include "hid_report_helpers.h"
#include "hid_usages.h"
#include <bpf/bpf_tracing.h>
HID_BPF_CONFIG(
HID_DEVICE(BUS_ANY, HID_GROUP_MULTITOUCH_WIN_8, HID_VID_ANY, HID_PID_ANY),
);
EXPORT_UDEV_PROP(HID_DIGITIZER_PAD_TYPE, 32);
__u8 hw_req_buf[1024];
/* to be filled by udev-hid-bpf */
struct hid_rdesc_descriptor HID_REPORT_DESCRIPTOR;
SEC("syscall")
int probe(struct hid_bpf_probe_args *ctx)
{
struct hid_rdesc_report *pad_type_feature = NULL;
struct hid_rdesc_field *pad_type = NULL;
struct hid_rdesc_report *feature;
struct hid_bpf_ctx *hid_ctx;
char *pad_type_str = "";
int ret;
hid_bpf_for_each_feature_report(&HID_REPORT_DESCRIPTOR, feature) {
struct hid_rdesc_field *field;
hid_bpf_for_each_field(feature, field) {
if (field->usage_page == HidUsagePage_Digitizers &&
field->usage_id == HidUsage_Dig_PadType) {
pad_type = field;
pad_type_feature = feature;
break;
}
}
if (pad_type)
break;
}
if (!pad_type || !pad_type_feature) {
ctx->retval = -EINVAL;
return 0;
}
hid_ctx = hid_bpf_allocate_context(ctx->hid);
if (!hid_ctx)
return -1; /* EPERM check */
hw_req_buf[0] = pad_type_feature->report_id;
ret = hid_bpf_hw_request(hid_ctx, hw_req_buf, sizeof(hw_req_buf),
HID_FEATURE_REPORT, HID_REQ_GET_REPORT);
hid_bpf_release_context(hid_ctx);
if (ret < 0) {
ctx->retval = ret;
return 0;
}
ctx->retval = 0;
switch (EXTRACT_BITS(hw_req_buf, pad_type)) {
case 0:
pad_type_str = "Clickpad";
break;
case 1:
pad_type_str = "Pressurepad";
break;
case 2:
pad_type_str = "Discrete";
break;
default:
pad_type_str = "Unknown";
}
UDEV_PROP_SPRINTF(HID_DIGITIZER_PAD_TYPE, "%s", pad_type_str);
return 0;
}
char _license[] SEC("license") = "GPL";
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