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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/samples/hid/hid_surface_dial.bpf.c
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// SPDX-License-Identifier: GPL-2.0-only

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/* Copyright (c) 2022 Benjamin Tissoires

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 */

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#include "vmlinux.h"

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#include <bpf/bpf_helpers.h>

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#include <bpf/bpf_tracing.h>

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#include "hid_bpf_helpers.h"

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#define HID_UP_BUTTON		0x0009

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#define HID_GD_WHEEL		0x0038

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SEC("struct_ops/hid_device_event")

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int BPF_PROG(hid_event, struct hid_bpf_ctx *hctx)

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{

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	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 9 /* size */);

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	if (!data)

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		return 0; /* EPERM check */

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	/* Touch */

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	data[1] &= 0xfd;

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	/* X */

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	data[4] = 0;

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	data[5] = 0;

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	/* Y */

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	data[6] = 0;

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	data[7] = 0;

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	return 0;

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}

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/* 72 == 360 / 5 -> 1 report every 5 degrees */

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int resolution = 72;

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int physical = 5;

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struct haptic_syscall_args {

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	unsigned int hid;

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	int retval;

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};

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static __u8 haptic_data[8];

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SEC("syscall")

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int set_haptic(struct haptic_syscall_args *args)

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{

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	struct hid_bpf_ctx *ctx;

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	const size_t size = sizeof(haptic_data);

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	u16 *res;

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	int ret;

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	if (size > sizeof(haptic_data))

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		return -7; /* -E2BIG */

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	ctx = hid_bpf_allocate_context(args->hid);

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	if (!ctx)

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		return -1; /* EPERM check */

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	haptic_data[0] = 1;  /* report ID */

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	ret = hid_bpf_hw_request(ctx, haptic_data, size, HID_FEATURE_REPORT, HID_REQ_GET_REPORT);

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	bpf_printk("probed/remove event ret value: %d", ret);

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	bpf_printk("buf: %02x %02x %02x",

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		   haptic_data[0],

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		   haptic_data[1],

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		   haptic_data[2]);

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	bpf_printk("     %02x %02x %02x",

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		   haptic_data[3],

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		   haptic_data[4],

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		   haptic_data[5]);

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	bpf_printk("     %02x %02x",

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		   haptic_data[6],

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		   haptic_data[7]);

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	/* whenever resolution multiplier is not 3600, we have the fixed report descriptor */

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	res = (u16 *)&haptic_data[1];

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	if (*res != 3600) {

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//		haptic_data[1] = 72; /* resolution multiplier */

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//		haptic_data[2] = 0;  /* resolution multiplier */

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//		haptic_data[3] = 0;  /* Repeat Count */

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		haptic_data[4] = 3;  /* haptic Auto Trigger */

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//		haptic_data[5] = 5;  /* Waveform Cutoff Time */

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//		haptic_data[6] = 80; /* Retrigger Period */

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//		haptic_data[7] = 0;  /* Retrigger Period */

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	} else {

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		haptic_data[4] = 0;

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	}

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	ret = hid_bpf_hw_request(ctx, haptic_data, size, HID_FEATURE_REPORT, HID_REQ_SET_REPORT);

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	bpf_printk("set haptic ret value: %d -> %d", ret, haptic_data[4]);

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	args->retval = ret;

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	hid_bpf_release_context(ctx);

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	return 0;

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}

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/* Convert REL_DIAL into REL_WHEEL */

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SEC("struct_ops/hid_rdesc_fixup")

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int BPF_PROG(hid_rdesc_fixup, struct hid_bpf_ctx *hctx)

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{

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	__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);

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	__u16 *res, *phys;

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	if (!data)

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		return 0; /* EPERM check */

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	/* Convert TOUCH into a button */

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	data[31] = HID_UP_BUTTON;

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	data[33] = 2;

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	/* Convert REL_DIAL into REL_WHEEL */

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	data[45] = HID_GD_WHEEL;

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	/* Change Resolution Multiplier */

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	phys = (__u16 *)&data[61];

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	*phys = physical;

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	res = (__u16 *)&data[66];

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	*res = resolution;

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	/* Convert X,Y from Abs to Rel */

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	data[88] = 0x06;

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	data[98] = 0x06;

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	return 0;

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}

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SEC(".struct_ops.link")

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struct hid_bpf_ops surface_dial = {

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	.hid_rdesc_fixup = (void *)hid_rdesc_fixup,

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	.hid_device_event = (void *)hid_event,

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};

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char _license[] SEC("license") = "GPL";

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u32 _version SEC("version") = 1;

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