OpenCloudOS-Kernel/include/linux/surface_aggregator/controller.h

/* SPDX-License-Identifier: GPL-2.0+ */
/*
 * Surface System Aggregator Module (SSAM) controller interface.
 *
 * Main communication interface for the SSAM EC. Provides a controller
 * managing access and communication to and from the SSAM EC, as well as main
 * communication structures and definitions.
 *
 * Copyright (C) 2019-2020 Maximilian Luz <luzmaximilian@gmail.com>
 */

#ifndef _LINUX_SURFACE_AGGREGATOR_CONTROLLER_H
#define _LINUX_SURFACE_AGGREGATOR_CONTROLLER_H

#include <linux/completion.h>
#include <linux/device.h>
#include <linux/types.h>

#include <linux/surface_aggregator/serial_hub.h>


/* -- Main data types and definitions --------------------------------------- */

/**
 * enum ssam_event_flags - Flags for enabling/disabling SAM events
 * @SSAM_EVENT_SEQUENCED: The event will be sent via a sequenced data frame.
 */
enum ssam_event_flags {
	SSAM_EVENT_SEQUENCED = BIT(0),
};

/**
 * struct ssam_event - SAM event sent from the EC to the host.
 * @target_category: Target category of the event source. See &enum ssam_ssh_tc.
 * @target_id:       Target ID of the event source.
 * @command_id:      Command ID of the event.
 * @instance_id:     Instance ID of the event source.
 * @length:          Length of the event payload in bytes.
 * @data:            Event payload data.
 */
struct ssam_event {
	u8 target_category;
	u8 target_id;
	u8 command_id;
	u8 instance_id;
	u16 length;
	u8 data[];
};

/**
 * enum ssam_request_flags - Flags for SAM requests.
 *
 * @SSAM_REQUEST_HAS_RESPONSE:
 *	Specifies that the request expects a response. If not set, the request
 *	will be directly completed after its underlying packet has been
 *	transmitted. If set, the request transport system waits for a response
 *	of the request.
 *
 * @SSAM_REQUEST_UNSEQUENCED:
 *	Specifies that the request should be transmitted via an unsequenced
 *	packet. If set, the request must not have a response, meaning that this
 *	flag and the %SSAM_REQUEST_HAS_RESPONSE flag are mutually exclusive.
 */
enum ssam_request_flags {
	SSAM_REQUEST_HAS_RESPONSE = BIT(0),
	SSAM_REQUEST_UNSEQUENCED  = BIT(1),
};

/**
 * struct ssam_request - SAM request description.
 * @target_category: Category of the request's target. See &enum ssam_ssh_tc.
 * @target_id:       ID of the request's target.
 * @command_id:      Command ID of the request.
 * @instance_id:     Instance ID of the request's target.
 * @flags:           Flags for the request. See &enum ssam_request_flags.
 * @length:          Length of the request payload in bytes.
 * @payload:         Request payload data.
 *
 * This struct fully describes a SAM request with payload. It is intended to
 * help set up the actual transport struct, e.g. &struct ssam_request_sync,
 * and specifically its raw message data via ssam_request_write_data().
 */
struct ssam_request {
	u8 target_category;
	u8 target_id;
	u8 command_id;
	u8 instance_id;
	u16 flags;
	u16 length;
	const u8 *payload;
};

/**
 * struct ssam_response - Response buffer for SAM request.
 * @capacity: Capacity of the buffer, in bytes.
 * @length:   Length of the actual data stored in the memory pointed to by
 *            @pointer, in bytes. Set by the transport system.
 * @pointer:  Pointer to the buffer's memory, storing the response payload data.
 */
struct ssam_response {
	size_t capacity;
	size_t length;
	u8 *pointer;
};

struct ssam_controller;

struct ssam_controller *ssam_get_controller(void);
struct ssam_controller *ssam_client_bind(struct device *client);
int ssam_client_link(struct ssam_controller *ctrl, struct device *client);

struct device *ssam_controller_device(struct ssam_controller *c);

struct ssam_controller *ssam_controller_get(struct ssam_controller *c);
void ssam_controller_put(struct ssam_controller *c);

void ssam_controller_statelock(struct ssam_controller *c);
void ssam_controller_stateunlock(struct ssam_controller *c);

ssize_t ssam_request_write_data(struct ssam_span *buf,
				struct ssam_controller *ctrl,
				const struct ssam_request *spec);


/* -- Synchronous request interface. ---------------------------------------- */

/**
 * struct ssam_request_sync - Synchronous SAM request struct.
 * @base:   Underlying SSH request.
 * @comp:   Completion used to signal full completion of the request. After the
 *          request has been submitted, this struct may only be modified or
 *          deallocated after the completion has been signaled.
 *          request has been submitted,
 * @resp:   Buffer to store the response.
 * @status: Status of the request, set after the base request has been
 *          completed or has failed.
 */
struct ssam_request_sync {
	struct ssh_request base;
	struct completion comp;
	struct ssam_response *resp;
	int status;
};

int ssam_request_sync_alloc(size_t payload_len, gfp_t flags,
			    struct ssam_request_sync **rqst,
			    struct ssam_span *buffer);

void ssam_request_sync_free(struct ssam_request_sync *rqst);

int ssam_request_sync_init(struct ssam_request_sync *rqst,
			   enum ssam_request_flags flags);

/**
 * ssam_request_sync_set_data - Set message data of a synchronous request.
 * @rqst: The request.
 * @ptr:  Pointer to the request message data.
 * @len:  Length of the request message data.
 *
 * Set the request message data of a synchronous request. The provided buffer
 * needs to live until the request has been completed.
 */
static inline void ssam_request_sync_set_data(struct ssam_request_sync *rqst,
					      u8 *ptr, size_t len)
{
	ssh_request_set_data(&rqst->base, ptr, len);
}

/**
 * ssam_request_sync_set_resp - Set response buffer of a synchronous request.
 * @rqst: The request.
 * @resp: The response buffer.
 *
 * Sets the response buffer of a synchronous request. This buffer will store
 * the response of the request after it has been completed. May be %NULL if no
 * response is expected.
 */
static inline void ssam_request_sync_set_resp(struct ssam_request_sync *rqst,
					      struct ssam_response *resp)
{
	rqst->resp = resp;
}

int ssam_request_sync_submit(struct ssam_controller *ctrl,
			     struct ssam_request_sync *rqst);

/**
 * ssam_request_sync_wait - Wait for completion of a synchronous request.
 * @rqst: The request to wait for.
 *
 * Wait for completion and release of a synchronous request. After this
 * function terminates, the request is guaranteed to have left the transport
 * system. After successful submission of a request, this function must be
 * called before accessing the response of the request, freeing the request,
 * or freeing any of the buffers associated with the request.
 *
 * This function must not be called if the request has not been submitted yet
 * and may lead to a deadlock/infinite wait if a subsequent request submission
 * fails in that case, due to the completion never triggering.
 *
 * Return: Returns the status of the given request, which is set on completion
 * of the packet. This value is zero on success and negative on failure.
 */
static inline int ssam_request_sync_wait(struct ssam_request_sync *rqst)
{
	wait_for_completion(&rqst->comp);
	return rqst->status;
}

int ssam_request_sync(struct ssam_controller *ctrl,
		      const struct ssam_request *spec,
		      struct ssam_response *rsp);

int ssam_request_sync_with_buffer(struct ssam_controller *ctrl,
				  const struct ssam_request *spec,
				  struct ssam_response *rsp,
				  struct ssam_span *buf);

/**
 * ssam_request_sync_onstack - Execute a synchronous request on the stack.
 * @ctrl: The controller via which the request is submitted.
 * @rqst: The request specification.
 * @rsp:  The response buffer.
 * @payload_len: The (maximum) request payload length.
 *
 * Allocates a synchronous request with specified payload length on the stack,
 * fully initializes it via the provided request specification, submits it,
 * and finally waits for its completion before returning its status. This
 * helper macro essentially allocates the request message buffer on the stack
 * and then calls ssam_request_sync_with_buffer().
 *
 * Note: The @payload_len parameter specifies the maximum payload length, used
 * for buffer allocation. The actual payload length may be smaller.
 *
 * Return: Returns the status of the request or any failure during setup, i.e.
 * zero on success and a negative value on failure.
 */
#define ssam_request_sync_onstack(ctrl, rqst, rsp, payload_len)			\
	({									\
		u8 __data[SSH_COMMAND_MESSAGE_LENGTH(payload_len)];		\
		struct ssam_span __buf = { &__data[0], ARRAY_SIZE(__data) };	\
										\
		ssam_request_sync_with_buffer(ctrl, rqst, rsp, &__buf);		\
	})

/**
 * __ssam_retry - Retry request in case of I/O errors or timeouts.
 * @request: The request function to execute. Must return an integer.
 * @n:       Number of tries.
 * @args:    Arguments for the request function.
 *
 * Executes the given request function, i.e. calls @request. In case the
 * request returns %-EREMOTEIO (indicates I/O error) or %-ETIMEDOUT (request
 * or underlying packet timed out), @request will be re-executed again, up to
 * @n times in total.
 *
 * Return: Returns the return value of the last execution of @request.
 */
#define __ssam_retry(request, n, args...)				\
	({								\
		int __i, __s = 0;					\
									\
		for (__i = (n); __i > 0; __i--) {			\
			__s = request(args);				\
			if (__s != -ETIMEDOUT && __s != -EREMOTEIO)	\
				break;					\
		}							\
		__s;							\
	})

/**
 * ssam_retry - Retry request in case of I/O errors or timeouts up to three
 * times in total.
 * @request: The request function to execute. Must return an integer.
 * @args:    Arguments for the request function.
 *
 * Executes the given request function, i.e. calls @request. In case the
 * request returns %-EREMOTEIO (indicates I/O error) or -%ETIMEDOUT (request
 * or underlying packet timed out), @request will be re-executed again, up to
 * three times in total.
 *
 * See __ssam_retry() for a more generic macro for this purpose.
 *
 * Return: Returns the return value of the last execution of @request.
 */
#define ssam_retry(request, args...) \
	__ssam_retry(request, 3, args)

/**
 * struct ssam_request_spec - Blue-print specification of SAM request.
 * @target_category: Category of the request's target. See &enum ssam_ssh_tc.
 * @target_id:       ID of the request's target.
 * @command_id:      Command ID of the request.
 * @instance_id:     Instance ID of the request's target.
 * @flags:           Flags for the request. See &enum ssam_request_flags.
 *
 * Blue-print specification for a SAM request. This struct describes the
 * unique static parameters of a request (i.e. type) without specifying any of
 * its instance-specific data (e.g. payload). It is intended to be used as base
 * for defining simple request functions via the
 * ``SSAM_DEFINE_SYNC_REQUEST_x()`` family of macros.
 */
struct ssam_request_spec {
	u8 target_category;
	u8 target_id;
	u8 command_id;
	u8 instance_id;
	u8 flags;
};

/**
 * struct ssam_request_spec_md - Blue-print specification for multi-device SAM
 * request.
 * @target_category: Category of the request's target. See &enum ssam_ssh_tc.
 * @command_id:      Command ID of the request.
 * @flags:           Flags for the request. See &enum ssam_request_flags.
 *
 * Blue-print specification for a multi-device SAM request, i.e. a request
 * that is applicable to multiple device instances, described by their
 * individual target and instance IDs. This struct describes the unique static
 * parameters of a request (i.e. type) without specifying any of its
 * instance-specific data (e.g. payload) and without specifying any of its
 * device specific IDs (i.e. target and instance ID). It is intended to be
 * used as base for defining simple multi-device request functions via the
 * ``SSAM_DEFINE_SYNC_REQUEST_MD_x()`` and ``SSAM_DEFINE_SYNC_REQUEST_CL_x()``
 * families of macros.
 */
struct ssam_request_spec_md {
	u8 target_category;
	u8 command_id;
	u8 flags;
};

/**
 * SSAM_DEFINE_SYNC_REQUEST_N() - Define synchronous SAM request function
 * with neither argument nor return value.
 * @name: Name of the generated function.
 * @spec: Specification (&struct ssam_request_spec) defining the request.
 *
 * Defines a function executing the synchronous SAM request specified by
 * @spec, with the request having neither argument nor return value. The
 * generated function takes care of setting up the request struct and buffer
 * allocation, as well as execution of the request itself, returning once the
 * request has been fully completed. The required transport buffer will be
 * allocated on the stack.
 *
 * The generated function is defined as ``static int name(struct
 * ssam_controller *ctrl)``, returning the status of the request, which is
 * zero on success and negative on failure. The ``ctrl`` parameter is the
 * controller via which the request is being sent.
 *
 * Refer to ssam_request_sync_onstack() for more details on the behavior of
 * the generated function.
 */
#define SSAM_DEFINE_SYNC_REQUEST_N(name, spec...)				\
	static int name(struct ssam_controller *ctrl)				\
	{									\
		struct ssam_request_spec s = (struct ssam_request_spec)spec;	\
		struct ssam_request rqst;					\
										\
		rqst.target_category = s.target_category;			\
		rqst.target_id = s.target_id;					\
		rqst.command_id = s.command_id;					\
		rqst.instance_id = s.instance_id;				\
		rqst.flags = s.flags;						\
		rqst.length = 0;						\
		rqst.payload = NULL;						\
										\
		return ssam_request_sync_onstack(ctrl, &rqst, NULL, 0);		\
	}

/**
 * SSAM_DEFINE_SYNC_REQUEST_W() - Define synchronous SAM request function with
 * argument.
 * @name:  Name of the generated function.
 * @atype: Type of the request's argument.
 * @spec:  Specification (&struct ssam_request_spec) defining the request.
 *
 * Defines a function executing the synchronous SAM request specified by
 * @spec, with the request taking an argument of type @atype and having no
 * return value. The generated function takes care of setting up the request
 * struct, buffer allocation, as well as execution of the request itself,
 * returning once the request has been fully completed. The required transport
 * buffer will be allocated on the stack.
 *
 * The generated function is defined as ``static int name(struct
 * ssam_controller *ctrl, const atype *arg)``, returning the status of the
 * request, which is zero on success and negative on failure. The ``ctrl``
 * parameter is the controller via which the request is sent. The request
 * argument is specified via the ``arg`` pointer.
 *
 * Refer to ssam_request_sync_onstack() for more details on the behavior of
 * the generated function.
 */
#define SSAM_DEFINE_SYNC_REQUEST_W(name, atype, spec...)			\
	static int name(struct ssam_controller *ctrl, const atype *arg)		\
	{									\
		struct ssam_request_spec s = (struct ssam_request_spec)spec;	\
		struct ssam_request rqst;					\
										\
		rqst.target_category = s.target_category;			\
		rqst.target_id = s.target_id;					\
		rqst.command_id = s.command_id;					\
		rqst.instance_id = s.instance_id;				\
		rqst.flags = s.flags;						\
		rqst.length = sizeof(atype);					\
		rqst.payload = (u8 *)arg;					\
										\
		return ssam_request_sync_onstack(ctrl, &rqst, NULL,		\
						 sizeof(atype));		\
	}

/**
 * SSAM_DEFINE_SYNC_REQUEST_R() - Define synchronous SAM request function with
 * return value.
 * @name:  Name of the generated function.
 * @rtype: Type of the request's return value.
 * @spec:  Specification (&struct ssam_request_spec) defining the request.
 *
 * Defines a function executing the synchronous SAM request specified by
 * @spec, with the request taking no argument but having a return value of
 * type @rtype. The generated function takes care of setting up the request
 * and response structs, buffer allocation, as well as execution of the
 * request itself, returning once the request has been fully completed. The
 * required transport buffer will be allocated on the stack.
 *
 * The generated function is defined as ``static int name(struct
 * ssam_controller *ctrl, rtype *ret)``, returning the status of the request,
 * which is zero on success and negative on failure. The ``ctrl`` parameter is
 * the controller via which the request is sent. The request's return value is
 * written to the memory pointed to by the ``ret`` parameter.
 *
 * Refer to ssam_request_sync_onstack() for more details on the behavior of
 * the generated function.
 */
#define SSAM_DEFINE_SYNC_REQUEST_R(name, rtype, spec...)			\
	static int name(struct ssam_controller *ctrl, rtype *ret)		\
	{									\
		struct ssam_request_spec s = (struct ssam_request_spec)spec;	\
		struct ssam_request rqst;					\
		struct ssam_response rsp;					\
		int status;							\
										\
		rqst.target_category = s.target_category;			\
		rqst.target_id = s.target_id;					\
		rqst.command_id = s.command_id;					\
		rqst.instance_id = s.instance_id;				\
		rqst.flags = s.flags | SSAM_REQUEST_HAS_RESPONSE;		\
		rqst.length = 0;						\
		rqst.payload = NULL;						\
										\
		rsp.capacity = sizeof(rtype);					\
		rsp.length = 0;							\
		rsp.pointer = (u8 *)ret;					\
										\
		status = ssam_request_sync_onstack(ctrl, &rqst, &rsp, 0);	\
		if (status)							\
			return status;						\
										\
		if (rsp.length != sizeof(rtype)) {				\
			struct device *dev = ssam_controller_device(ctrl);	\
			dev_err(dev,						\
				"rqst: invalid response length, expected %zu, got %zu (tc: %#04x, cid: %#04x)", \
				sizeof(rtype), rsp.length, rqst.target_category,\
				rqst.command_id);				\
			return -EIO;						\
		}								\
										\
		return 0;							\
	}

/**
 * SSAM_DEFINE_SYNC_REQUEST_MD_N() - Define synchronous multi-device SAM
 * request function with neither argument nor return value.
 * @name: Name of the generated function.
 * @spec: Specification (&struct ssam_request_spec_md) defining the request.
 *
 * Defines a function executing the synchronous SAM request specified by
 * @spec, with the request having neither argument nor return value. Device
 * specifying parameters are not hard-coded, but instead must be provided to
 * the function. The generated function takes care of setting up the request
 * struct, buffer allocation, as well as execution of the request itself,
 * returning once the request has been fully completed. The required transport
 * buffer will be allocated on the stack.
 *
 * The generated function is defined as ``static int name(struct
 * ssam_controller *ctrl, u8 tid, u8 iid)``, returning the status of the
 * request, which is zero on success and negative on failure. The ``ctrl``
 * parameter is the controller via which the request is sent, ``tid`` the
 * target ID for the request, and ``iid`` the instance ID.
 *
 * Refer to ssam_request_sync_onstack() for more details on the behavior of
 * the generated function.
 */
#define SSAM_DEFINE_SYNC_REQUEST_MD_N(name, spec...)				\
	static int name(struct ssam_controller *ctrl, u8 tid, u8 iid)		\
	{									\
		struct ssam_request_spec_md s = (struct ssam_request_spec_md)spec; \
		struct ssam_request rqst;					\
										\
		rqst.target_category = s.target_category;			\
		rqst.target_id = tid;						\
		rqst.command_id = s.command_id;					\
		rqst.instance_id = iid;						\
		rqst.flags = s.flags;						\
		rqst.length = 0;						\
		rqst.payload = NULL;						\
										\
		return ssam_request_sync_onstack(ctrl, &rqst, NULL, 0);		\
	}

/**
 * SSAM_DEFINE_SYNC_REQUEST_MD_W() - Define synchronous multi-device SAM
 * request function with argument.
 * @name:  Name of the generated function.
 * @atype: Type of the request's argument.
 * @spec:  Specification (&struct ssam_request_spec_md) defining the request.
 *
 * Defines a function executing the synchronous SAM request specified by
 * @spec, with the request taking an argument of type @atype and having no
 * return value. Device specifying parameters are not hard-coded, but instead
 * must be provided to the function. The generated function takes care of
 * setting up the request struct, buffer allocation, as well as execution of
 * the request itself, returning once the request has been fully completed.
 * The required transport buffer will be allocated on the stack.
 *
 * The generated function is defined as ``static int name(struct
 * ssam_controller *ctrl, u8 tid, u8 iid, const atype *arg)``, returning the
 * status of the request, which is zero on success and negative on failure.
 * The ``ctrl`` parameter is the controller via which the request is sent,
 * ``tid`` the target ID for the request, and ``iid`` the instance ID. The
 * request argument is specified via the ``arg`` pointer.
 *
 * Refer to ssam_request_sync_onstack() for more details on the behavior of
 * the generated function.
 */
#define SSAM_DEFINE_SYNC_REQUEST_MD_W(name, atype, spec...)			\
	static int name(struct ssam_controller *ctrl, u8 tid, u8 iid, const atype *arg) \
	{									\
		struct ssam_request_spec_md s = (struct ssam_request_spec_md)spec; \
		struct ssam_request rqst;					\
										\
		rqst.target_category = s.target_category;			\
		rqst.target_id = tid;						\
		rqst.command_id = s.command_id;					\
		rqst.instance_id = iid;						\
		rqst.flags = s.flags;						\
		rqst.length = sizeof(atype);					\
		rqst.payload = (u8 *)arg;					\
										\
		return ssam_request_sync_onstack(ctrl, &rqst, NULL,		\
						 sizeof(atype));		\
	}

/**
 * SSAM_DEFINE_SYNC_REQUEST_MD_R() - Define synchronous multi-device SAM
 * request function with return value.
 * @name:  Name of the generated function.
 * @rtype: Type of the request's return value.
 * @spec:  Specification (&struct ssam_request_spec_md) defining the request.
 *
 * Defines a function executing the synchronous SAM request specified by
 * @spec, with the request taking no argument but having a return value of
 * type @rtype. Device specifying parameters are not hard-coded, but instead
 * must be provided to the function. The generated function takes care of
 * setting up the request and response structs, buffer allocation, as well as
 * execution of the request itself, returning once the request has been fully
 * completed. The required transport buffer will be allocated on the stack.
 *
 * The generated function is defined as ``static int name(struct
 * ssam_controller *ctrl, u8 tid, u8 iid, rtype *ret)``, returning the status
 * of the request, which is zero on success and negative on failure. The
 * ``ctrl`` parameter is the controller via which the request is sent, ``tid``
 * the target ID for the request, and ``iid`` the instance ID. The request's
 * return value is written to the memory pointed to by the ``ret`` parameter.
 *
 * Refer to ssam_request_sync_onstack() for more details on the behavior of
 * the generated function.
 */
#define SSAM_DEFINE_SYNC_REQUEST_MD_R(name, rtype, spec...)			\
	static int name(struct ssam_controller *ctrl, u8 tid, u8 iid, rtype *ret) \
	{									\
		struct ssam_request_spec_md s = (struct ssam_request_spec_md)spec; \
		struct ssam_request rqst;					\
		struct ssam_response rsp;					\
		int status;							\
										\
		rqst.target_category = s.target_category;			\
		rqst.target_id = tid;						\
		rqst.command_id = s.command_id;					\
		rqst.instance_id = iid;						\
		rqst.flags = s.flags | SSAM_REQUEST_HAS_RESPONSE;		\
		rqst.length = 0;						\
		rqst.payload = NULL;						\
										\
		rsp.capacity = sizeof(rtype);					\
		rsp.length = 0;							\
		rsp.pointer = (u8 *)ret;					\
										\
		status = ssam_request_sync_onstack(ctrl, &rqst, &rsp, 0);	\
		if (status)							\
			return status;						\
										\
		if (rsp.length != sizeof(rtype)) {				\
			struct device *dev = ssam_controller_device(ctrl);	\
			dev_err(dev,						\
				"rqst: invalid response length, expected %zu, got %zu (tc: %#04x, cid: %#04x)", \
				sizeof(rtype), rsp.length, rqst.target_category,\
				rqst.command_id);				\
			return -EIO;						\
		}								\
										\
		return 0;							\
	}


/* -- Event notifier/callbacks. --------------------------------------------- */

#define SSAM_NOTIF_STATE_SHIFT		2
#define SSAM_NOTIF_STATE_MASK		((1 << SSAM_NOTIF_STATE_SHIFT) - 1)

/**
 * enum ssam_notif_flags - Flags used in return values from SSAM notifier
 * callback functions.
 *
 * @SSAM_NOTIF_HANDLED:
 *	Indicates that the notification has been handled. This flag should be
 *	set by the handler if the handler can act/has acted upon the event
 *	provided to it. This flag should not be set if the handler is not a
 *	primary handler intended for the provided event.
 *
 *	If this flag has not been set by any handler after the notifier chain
 *	has been traversed, a warning will be emitted, stating that the event
 *	has not been handled.
 *
 * @SSAM_NOTIF_STOP:
 *	Indicates that the notifier traversal should stop. If this flag is
 *	returned from a notifier callback, notifier chain traversal will
 *	immediately stop and any remaining notifiers will not be called. This
 *	flag is automatically set when ssam_notifier_from_errno() is called
 *	with a negative error value.
 */
enum ssam_notif_flags {
	SSAM_NOTIF_HANDLED = BIT(0),
	SSAM_NOTIF_STOP    = BIT(1),
};

struct ssam_event_notifier;

typedef u32 (*ssam_notifier_fn_t)(struct ssam_event_notifier *nf,
				  const struct ssam_event *event);

/**
 * struct ssam_notifier_block - Base notifier block for SSAM event
 * notifications.
 * @node:     The node for the list of notifiers.
 * @fn:       The callback function of this notifier. This function takes the
 *            respective notifier block and event as input and should return
 *            a notifier value, which can either be obtained from the flags
 *            provided in &enum ssam_notif_flags, converted from a standard
 *            error value via ssam_notifier_from_errno(), or a combination of
 *            both (e.g. ``ssam_notifier_from_errno(e) | SSAM_NOTIF_HANDLED``).
 * @priority: Priority value determining the order in which notifier callbacks
 *            will be called. A higher value means higher priority, i.e. the
 *            associated callback will be executed earlier than other (lower
 *            priority) callbacks.
 */
struct ssam_notifier_block {
	struct list_head node;
	ssam_notifier_fn_t fn;
	int priority;
};

/**
 * ssam_notifier_from_errno() - Convert standard error value to notifier
 * return code.
 * @err: The error code to convert, must be negative (in case of failure) or
 *       zero (in case of success).
 *
 * Return: Returns the notifier return value obtained by converting the
 * specified @err value. In case @err is negative, the %SSAM_NOTIF_STOP flag
 * will be set, causing notifier call chain traversal to abort.
 */
static inline u32 ssam_notifier_from_errno(int err)
{
	if (WARN_ON(err > 0) || err == 0)
		return 0;
	else
		return ((-err) << SSAM_NOTIF_STATE_SHIFT) | SSAM_NOTIF_STOP;
}

/**
 * ssam_notifier_to_errno() - Convert notifier return code to standard error
 * value.
 * @ret: The notifier return value to convert.
 *
 * Return: Returns the negative error value encoded in @ret or zero if @ret
 * indicates success.
 */
static inline int ssam_notifier_to_errno(u32 ret)
{
	return -(ret >> SSAM_NOTIF_STATE_SHIFT);
}


/* -- Event/notification registry. ------------------------------------------ */

/**
 * struct ssam_event_registry - Registry specification used for enabling events.
 * @target_category: Target category for the event registry requests.
 * @target_id:       Target ID for the event registry requests.
 * @cid_enable:      Command ID for the event-enable request.
 * @cid_disable:     Command ID for the event-disable request.
 *
 * This struct describes a SAM event registry via the minimal collection of
 * SAM IDs specifying the requests to use for enabling and disabling an event.
 * The individual event to be enabled/disabled itself is specified via &struct
 * ssam_event_id.
 */
struct ssam_event_registry {
	u8 target_category;
	u8 target_id;
	u8 cid_enable;
	u8 cid_disable;
};

/**
 * struct ssam_event_id - Unique event ID used for enabling events.
 * @target_category: Target category of the event source.
 * @instance:        Instance ID of the event source.
 *
 * This struct specifies the event to be enabled/disabled via an externally
 * provided registry. It does not specify the registry to be used itself, this
 * is done via &struct ssam_event_registry.
 */
struct ssam_event_id {
	u8 target_category;
	u8 instance;
};

/**
 * enum ssam_event_mask - Flags specifying how events are matched to notifiers.
 *
 * @SSAM_EVENT_MASK_NONE:
 *	Run the callback for any event with matching target category. Do not
 *	do any additional filtering.
 *
 * @SSAM_EVENT_MASK_TARGET:
 *	In addition to filtering by target category, only execute the notifier
 *	callback for events with a target ID matching to the one of the
 *	registry used for enabling/disabling the event.
 *
 * @SSAM_EVENT_MASK_INSTANCE:
 *	In addition to filtering by target category, only execute the notifier
 *	callback for events with an instance ID matching to the instance ID
 *	used when enabling the event.
 *
 * @SSAM_EVENT_MASK_STRICT:
 *	Do all the filtering above.
 */
enum ssam_event_mask {
	SSAM_EVENT_MASK_TARGET   = BIT(0),
	SSAM_EVENT_MASK_INSTANCE = BIT(1),

	SSAM_EVENT_MASK_NONE = 0,
	SSAM_EVENT_MASK_STRICT =
		  SSAM_EVENT_MASK_TARGET
		| SSAM_EVENT_MASK_INSTANCE,
};

/**
 * SSAM_EVENT_REGISTRY() - Define a new event registry.
 * @tc:      Target category for the event registry requests.
 * @tid:     Target ID for the event registry requests.
 * @cid_en:  Command ID for the event-enable request.
 * @cid_dis: Command ID for the event-disable request.
 *
 * Return: Returns the &struct ssam_event_registry specified by the given
 * parameters.
 */
#define SSAM_EVENT_REGISTRY(tc, tid, cid_en, cid_dis)	\
	((struct ssam_event_registry) {			\
		.target_category = (tc),		\
		.target_id = (tid),			\
		.cid_enable = (cid_en),			\
		.cid_disable = (cid_dis),		\
	})

#define SSAM_EVENT_REGISTRY_SAM	\
	SSAM_EVENT_REGISTRY(SSAM_SSH_TC_SAM, 0x01, 0x0b, 0x0c)

#define SSAM_EVENT_REGISTRY_KIP	\
	SSAM_EVENT_REGISTRY(SSAM_SSH_TC_KIP, 0x02, 0x27, 0x28)

#define SSAM_EVENT_REGISTRY_REG \
	SSAM_EVENT_REGISTRY(SSAM_SSH_TC_REG, 0x02, 0x01, 0x02)

/**
 * enum ssam_event_notifier_flags - Flags for event notifiers.
 * @SSAM_EVENT_NOTIFIER_OBSERVER:
 *	The corresponding notifier acts as observer. Registering a notifier
 *	with this flag set will not attempt to enable any event. Equally,
 *	unregistering will not attempt to disable any event. Note that a
 *	notifier with this flag may not even correspond to a certain event at
 *	all, only to a specific event target category. Event matching will not
 *	be influenced by this flag.
 */
enum ssam_event_notifier_flags {
	SSAM_EVENT_NOTIFIER_OBSERVER = BIT(0),
};

/**
 * struct ssam_event_notifier - Notifier block for SSAM events.
 * @base:        The base notifier block with callback function and priority.
 * @event:       The event for which this block will receive notifications.
 * @event.reg:   Registry via which the event will be enabled/disabled.
 * @event.id:    ID specifying the event.
 * @event.mask:  Flags determining how events are matched to the notifier.
 * @event.flags: Flags used for enabling the event.
 * @flags:       Notifier flags (see &enum ssam_event_notifier_flags).
 */
struct ssam_event_notifier {
	struct ssam_notifier_block base;

	struct {
		struct ssam_event_registry reg;
		struct ssam_event_id id;
		enum ssam_event_mask mask;
		u8 flags;
	} event;

	unsigned long flags;
};

int ssam_notifier_register(struct ssam_controller *ctrl,
			   struct ssam_event_notifier *n);

int ssam_notifier_unregister(struct ssam_controller *ctrl,
			     struct ssam_event_notifier *n);

int ssam_controller_event_enable(struct ssam_controller *ctrl,
				 struct ssam_event_registry reg,
				 struct ssam_event_id id, u8 flags);

int ssam_controller_event_disable(struct ssam_controller *ctrl,
				  struct ssam_event_registry reg,
				  struct ssam_event_id id, u8 flags);

#endif /* _LINUX_SURFACE_AGGREGATOR_CONTROLLER_H */