Commit af79443b authored by Benjamin Tissoires's avatar Benjamin Tissoires Committed by Jiri Kosina
Browse files

HID: bpf: add a BPF to get the touchpad type 



Currently the kernel is scheduled to do this call by itself, but it
requires a kernel v6.18 at least to have the INPUT_PROP set. For older
kernels, we can try to query the property from a HID-BPF probe, and set
a udev property based on that. This way we can provide the information
to old kernels without modifying them.

Signed-off-by: default avatarBenjamin Tissoires <benjamin.tissoires@gmail.com>
Link: https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/220


Signed-off-by: default avatarBenjamin Tissoires <bentiss@kernel.org>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.com>
parent bb8be68d

drivers/hid/bpf/progs/Generic__touchpad.bpf.c

0 → 100644
+90 −0
Original line number Diff line number Diff line 
// 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";