/* SPDX-License-Identifier: GPL-2.0+ */

#ifndef __HID_BPF_H
#define __HID_BPF_H

#include <linux/spinlock.h>
#include <uapi/linux/hid.h>

struct hid_device;

/*
 * The following is the user facing HID BPF API.
 *
 * Extra care should be taken when editing this part, as
 * it might break existing out of the tree bpf programs.
 */

/**
 * struct hid_bpf_ctx - User accessible data for all HID programs
 *
 * ``data`` is not directly accessible from the context. We need to issue
 * a call to ``hid_bpf_get_data()`` in order to get a pointer to that field.
 *
 * All of these fields are currently read-only.
 *
 * @index: program index in the jump table. No special meaning (a smaller index
 *         doesn't mean the program will be executed before another program with
 *         a bigger index).
 * @hid: the ``struct hid_device`` representing the device itself
 * @report_type: used for ``hid_bpf_device_event()``
 * @size: Valid data in the data field.
 *
 *        Programs can get the available valid size in data by fetching this field.
 */
struct hid_bpf_ctx {
	__u32 index;
	const struct hid_device *hid;
	enum hid_report_type report_type;
	__s32 size;
};

/**
 * enum hid_bpf_attach_flags - flags used when attaching a HIF-BPF program
 *
 * @HID_BPF_FLAG_NONE: no specific flag is used, the kernel choses where to
 *                     insert the program
 * @HID_BPF_FLAG_INSERT_HEAD: insert the given program before any other program
 *                            currently attached to the device. This doesn't
 *                            guarantee that this program will always be first
 * @HID_BPF_FLAG_MAX: sentinel value, not to be used by the callers
 */
enum hid_bpf_attach_flags {
	HID_BPF_FLAG_NONE = 0,
	HID_BPF_FLAG_INSERT_HEAD = _BITUL(0),
	HID_BPF_FLAG_MAX,
};

/* Following functions are tracepoints that BPF programs can attach to */
int hid_bpf_device_event(struct hid_bpf_ctx *ctx);

/* Following functions are kfunc that we export to BPF programs */
/* only available in tracing */
__u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx, unsigned int offset, const size_t __sz);

/* only available in syscall */
int hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, __u32 flags);

/*
 * Below is HID internal
 */

/* internal function to call eBPF programs, not to be used by anybody */
int __hid_bpf_tail_call(struct hid_bpf_ctx *ctx);

#define HID_BPF_MAX_PROGS_PER_DEV 64
#define HID_BPF_FLAG_MASK (((HID_BPF_FLAG_MAX - 1) << 1) - 1)

/* types of HID programs to attach to */
enum hid_bpf_prog_type {
	HID_BPF_PROG_TYPE_UNDEF = -1,
	HID_BPF_PROG_TYPE_DEVICE_EVENT,			/* an event is emitted from the device */
	HID_BPF_PROG_TYPE_MAX,
};

struct hid_bpf_ops {
	struct module *owner;
	struct bus_type *bus_type;
};

extern struct hid_bpf_ops *hid_bpf_ops;

struct hid_bpf_prog_list {
	u16 prog_idx[HID_BPF_MAX_PROGS_PER_DEV];
	u8 prog_cnt;
};

/* stored in each device */
struct hid_bpf {
	struct hid_bpf_prog_list __rcu *progs[HID_BPF_PROG_TYPE_MAX];	/* attached BPF progs */
	bool destroyed;			/* prevents the assignment of any progs */

	spinlock_t progs_lock;		/* protects RCU update of progs */
};

#ifdef CONFIG_HID_BPF
int dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type, u8 *data,
				  u32 size, int interrupt);
void hid_bpf_destroy_device(struct hid_device *hid);
void hid_bpf_device_init(struct hid_device *hid);
#else /* CONFIG_HID_BPF */
static inline int dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type,
						u8 *data, u32 size, int interrupt) { return 0; }
static inline void hid_bpf_destroy_device(struct hid_device *hid) {}
static inline void hid_bpf_device_init(struct hid_device *hid) {}
#endif /* CONFIG_HID_BPF */

#endif /* __HID_BPF_H */