1 /* SPDX-License-Identifier: GPL-2.0+ */
3 * Surface Serial Hub (SSH) protocol and communication interface.
5 * Lower-level communication layers and SSH protocol definitions for the
6 * Surface System Aggregator Module (SSAM). Provides the interface for basic
7 * packet- and request-based communication with the SSAM EC via SSH.
9 * Copyright (C) 2019-2020 Maximilian Luz <luzmaximilian@gmail.com>
12 #ifndef _LINUX_SURFACE_AGGREGATOR_SERIAL_HUB_H
13 #define _LINUX_SURFACE_AGGREGATOR_SERIAL_HUB_H
15 #include <linux/crc-ccitt.h>
16 #include <linux/kref.h>
17 #include <linux/ktime.h>
18 #include <linux/list.h>
19 #include <linux/types.h>
22 /* -- Data structures for SAM-over-SSH communication. ----------------------- */
25 * enum ssh_frame_type - Frame types for SSH frames.
27 * @SSH_FRAME_TYPE_DATA_SEQ:
28 * Indicates a data frame, followed by a payload with the length specified
29 * in the ``struct ssh_frame.len`` field. This frame is sequenced, meaning
30 * that an ACK is required.
32 * @SSH_FRAME_TYPE_DATA_NSQ:
33 * Same as %SSH_FRAME_TYPE_DATA_SEQ, but unsequenced, meaning that the
34 * message does not have to be ACKed.
36 * @SSH_FRAME_TYPE_ACK:
37 * Indicates an ACK message.
39 * @SSH_FRAME_TYPE_NAK:
40 * Indicates an error response for previously sent frame. In general, this
41 * means that the frame and/or payload is malformed, e.g. a CRC is wrong.
42 * For command-type payloads, this can also mean that the command is
46 SSH_FRAME_TYPE_DATA_SEQ = 0x80,
47 SSH_FRAME_TYPE_DATA_NSQ = 0x00,
48 SSH_FRAME_TYPE_ACK = 0x40,
49 SSH_FRAME_TYPE_NAK = 0x04,
53 * struct ssh_frame - SSH communication frame.
54 * @type: The type of the frame. See &enum ssh_frame_type.
55 * @len: The length of the frame payload directly following the CRC for this
56 * frame. Does not include the final CRC for that payload.
57 * @seq: The sequence number for this message/exchange.
65 static_assert(sizeof(struct ssh_frame) == 4);
68 * SSH_FRAME_MAX_PAYLOAD_SIZE - Maximum SSH frame payload length in bytes.
70 * This is the physical maximum length of the protocol. Implementations may
71 * set a more constrained limit.
73 #define SSH_FRAME_MAX_PAYLOAD_SIZE U16_MAX
76 * enum ssh_payload_type - Type indicator for the SSH payload.
77 * @SSH_PLD_TYPE_CMD: The payload is a command structure with optional command
80 enum ssh_payload_type {
81 SSH_PLD_TYPE_CMD = 0x80,
85 * struct ssh_command - Payload of a command-type frame.
86 * @type: The type of the payload. See &enum ssh_payload_type. Should be
87 * SSH_PLD_TYPE_CMD for this struct.
88 * @tc: Command target category.
89 * @tid_out: Output target ID. Should be zero if this an incoming (EC to host)
91 * @tid_in: Input target ID. Should be zero if this is an outgoing (host to
94 * @rqid: Request ID. Used to match requests with responses and differentiate
95 * between responses and events.
108 static_assert(sizeof(struct ssh_command) == 8);
111 * SSH_COMMAND_MAX_PAYLOAD_SIZE - Maximum SSH command payload length in bytes.
113 * This is the physical maximum length of the protocol. Implementations may
114 * set a more constrained limit.
116 #define SSH_COMMAND_MAX_PAYLOAD_SIZE \
117 (SSH_FRAME_MAX_PAYLOAD_SIZE - sizeof(struct ssh_command))
120 * SSH_MSG_LEN_BASE - Base-length of a SSH message.
122 * This is the minimum number of bytes required to form a message. The actual
123 * message length is SSH_MSG_LEN_BASE plus the length of the frame payload.
125 #define SSH_MSG_LEN_BASE (sizeof(struct ssh_frame) + 3ull * sizeof(u16))
128 * SSH_MSG_LEN_CTRL - Length of a SSH control message.
130 * This is the length of a SSH control message, which is equal to a SSH
131 * message without any payload.
133 #define SSH_MSG_LEN_CTRL SSH_MSG_LEN_BASE
136 * SSH_MESSAGE_LENGTH() - Compute length of SSH message.
137 * @payload_size: Length of the payload inside the SSH frame.
139 * Return: Returns the length of a SSH message with payload of specified size.
141 #define SSH_MESSAGE_LENGTH(payload_size) (SSH_MSG_LEN_BASE + (payload_size))
144 * SSH_COMMAND_MESSAGE_LENGTH() - Compute length of SSH command message.
145 * @payload_size: Length of the command payload.
147 * Return: Returns the length of a SSH command message with command payload of
150 #define SSH_COMMAND_MESSAGE_LENGTH(payload_size) \
151 SSH_MESSAGE_LENGTH(sizeof(struct ssh_command) + (payload_size))
154 * SSH_MSGOFFSET_FRAME() - Compute offset in SSH message to specified field in
156 * @field: The field for which the offset should be computed.
158 * Return: Returns the offset of the specified &struct ssh_frame field in the
159 * raw SSH message data as. Takes SYN bytes (u16) preceding the frame into
162 #define SSH_MSGOFFSET_FRAME(field) \
163 (sizeof(u16) + offsetof(struct ssh_frame, field))
166 * SSH_MSGOFFSET_COMMAND() - Compute offset in SSH message to specified field
168 * @field: The field for which the offset should be computed.
170 * Return: Returns the offset of the specified &struct ssh_command field in
171 * the raw SSH message data. Takes SYN bytes (u16) preceding the frame and the
172 * frame CRC (u16) between frame and command into account.
174 #define SSH_MSGOFFSET_COMMAND(field) \
175 (2ull * sizeof(u16) + sizeof(struct ssh_frame) \
176 + offsetof(struct ssh_command, field))
179 * SSH_MSG_SYN - SSH message synchronization (SYN) bytes as u16.
181 #define SSH_MSG_SYN ((u16)0x55aa)
184 * ssh_crc() - Compute CRC for SSH messages.
185 * @buf: The pointer pointing to the data for which the CRC should be computed.
186 * @len: The length of the data for which the CRC should be computed.
188 * Return: Returns the CRC computed on the provided data, as used for SSH
191 static inline u16 ssh_crc(const u8 *buf, size_t len)
193 return crc_ccitt_false(0xffff, buf, len);
197 * SSH_NUM_EVENTS - The number of reserved event IDs.
199 * The number of reserved event IDs, used for registering an SSH event
200 * handler. Valid event IDs are numbers below or equal to this value, with
201 * exception of zero, which is not an event ID. Thus, this is also the
202 * absolute maximum number of event handlers that can be registered.
204 #define SSH_NUM_EVENTS 34
207 * SSH_NUM_TARGETS - The number of communication targets used in the protocol.
209 #define SSH_NUM_TARGETS 2
212 * ssh_rqid_next_valid() - Return the next valid request ID.
213 * @rqid: The current request ID.
215 * Return: Returns the next valid request ID, following the current request ID
216 * provided to this function. This function skips any request IDs reserved for
219 static inline u16 ssh_rqid_next_valid(u16 rqid)
221 return rqid > 0 ? rqid + 1u : rqid + SSH_NUM_EVENTS + 1u;
225 * ssh_rqid_to_event() - Convert request ID to its corresponding event ID.
226 * @rqid: The request ID to convert.
228 static inline u16 ssh_rqid_to_event(u16 rqid)
234 * ssh_rqid_is_event() - Check if given request ID is a valid event ID.
235 * @rqid: The request ID to check.
237 static inline bool ssh_rqid_is_event(u16 rqid)
239 return ssh_rqid_to_event(rqid) < SSH_NUM_EVENTS;
243 * ssh_tc_to_rqid() - Convert target category to its corresponding request ID.
244 * @tc: The target category to convert.
246 static inline u16 ssh_tc_to_rqid(u8 tc)
252 * ssh_tid_to_index() - Convert target ID to its corresponding target index.
253 * @tid: The target ID to convert.
255 static inline u8 ssh_tid_to_index(u8 tid)
261 * ssh_tid_is_valid() - Check if target ID is valid/supported.
262 * @tid: The target ID to check.
264 static inline bool ssh_tid_is_valid(u8 tid)
266 return ssh_tid_to_index(tid) < SSH_NUM_TARGETS;
270 * struct ssam_span - Reference to a buffer region.
271 * @ptr: Pointer to the buffer region.
272 * @len: Length of the buffer region.
274 * A reference to a (non-owned) buffer segment, consisting of pointer and
275 * length. Use of this struct indicates non-owned data, i.e. data of which the
276 * life-time is managed (i.e. it is allocated/freed) via another pointer.
284 * Known SSH/EC target categories.
286 * List of currently known target category values; "Known" as in we know they
287 * exist and are valid on at least some device/model. Detailed functionality
288 * or the full category name is only known for some of these categories and
289 * is detailed in the respective comment below.
291 * These values and abbreviations have been extracted from strings inside the
295 /* Category 0x00 is invalid for EC use. */
296 SSAM_SSH_TC_SAM = 0x01, /* Generic system functionality, real-time clock. */
297 SSAM_SSH_TC_BAT = 0x02, /* Battery/power subsystem. */
298 SSAM_SSH_TC_TMP = 0x03, /* Thermal subsystem. */
299 SSAM_SSH_TC_PMC = 0x04,
300 SSAM_SSH_TC_FAN = 0x05,
301 SSAM_SSH_TC_PoM = 0x06,
302 SSAM_SSH_TC_DBG = 0x07,
303 SSAM_SSH_TC_KBD = 0x08, /* Legacy keyboard (Laptop 1/2). */
304 SSAM_SSH_TC_FWU = 0x09,
305 SSAM_SSH_TC_UNI = 0x0a,
306 SSAM_SSH_TC_LPC = 0x0b,
307 SSAM_SSH_TC_TCL = 0x0c,
308 SSAM_SSH_TC_SFL = 0x0d,
309 SSAM_SSH_TC_KIP = 0x0e,
310 SSAM_SSH_TC_EXT = 0x0f,
311 SSAM_SSH_TC_BLD = 0x10,
312 SSAM_SSH_TC_BAS = 0x11, /* Detachment system (Surface Book 2/3). */
313 SSAM_SSH_TC_SEN = 0x12,
314 SSAM_SSH_TC_SRQ = 0x13,
315 SSAM_SSH_TC_MCU = 0x14,
316 SSAM_SSH_TC_HID = 0x15, /* Generic HID input subsystem. */
317 SSAM_SSH_TC_TCH = 0x16,
318 SSAM_SSH_TC_BKL = 0x17,
319 SSAM_SSH_TC_TAM = 0x18,
320 SSAM_SSH_TC_ACC = 0x19,
321 SSAM_SSH_TC_UFI = 0x1a,
322 SSAM_SSH_TC_USC = 0x1b,
323 SSAM_SSH_TC_PEN = 0x1c,
324 SSAM_SSH_TC_VID = 0x1d,
325 SSAM_SSH_TC_AUD = 0x1e,
326 SSAM_SSH_TC_SMC = 0x1f,
327 SSAM_SSH_TC_KPD = 0x20,
328 SSAM_SSH_TC_REG = 0x21, /* Extended event registry. */
332 /* -- Packet transport layer (ptl). ----------------------------------------- */
335 * enum ssh_packet_base_priority - Base priorities for &struct ssh_packet.
336 * @SSH_PACKET_PRIORITY_FLUSH: Base priority for flush packets.
337 * @SSH_PACKET_PRIORITY_DATA: Base priority for normal data packets.
338 * @SSH_PACKET_PRIORITY_NAK: Base priority for NAK packets.
339 * @SSH_PACKET_PRIORITY_ACK: Base priority for ACK packets.
341 enum ssh_packet_base_priority {
342 SSH_PACKET_PRIORITY_FLUSH = 0, /* same as DATA to sequence flush */
343 SSH_PACKET_PRIORITY_DATA = 0,
344 SSH_PACKET_PRIORITY_NAK = 1,
345 SSH_PACKET_PRIORITY_ACK = 2,
349 * Same as SSH_PACKET_PRIORITY() below, only with actual values.
351 #define __SSH_PACKET_PRIORITY(base, try) \
352 (((base) << 4) | ((try) & 0x0f))
355 * SSH_PACKET_PRIORITY() - Compute packet priority from base priority and
357 * @base: The base priority as suffix of &enum ssh_packet_base_priority, e.g.
358 * ``FLUSH``, ``DATA``, ``ACK``, or ``NAK``.
359 * @try: The number of tries (must be less than 16).
361 * Compute the combined packet priority. The combined priority is dominated by
362 * the base priority, whereas the number of (re-)tries decides the precedence
363 * of packets with the same base priority, giving higher priority to packets
364 * that already have more tries.
366 * Return: Returns the computed priority as value fitting inside a &u8. A
367 * higher number means a higher priority.
369 #define SSH_PACKET_PRIORITY(base, try) \
370 __SSH_PACKET_PRIORITY(SSH_PACKET_PRIORITY_##base, (try))
373 * ssh_packet_priority_get_try() - Get number of tries from packet priority.
374 * @priority: The packet priority.
376 * Return: Returns the number of tries encoded in the specified packet
379 static inline u8 ssh_packet_priority_get_try(u8 priority)
381 return priority & 0x0f;
385 * ssh_packet_priority_get_base - Get base priority from packet priority.
386 * @priority: The packet priority.
388 * Return: Returns the base priority encoded in the given packet priority.
390 static inline u8 ssh_packet_priority_get_base(u8 priority)
392 return (priority & 0xf0) >> 4;
395 enum ssh_packet_flags {
397 SSH_PACKET_SF_LOCKED_BIT,
398 SSH_PACKET_SF_QUEUED_BIT,
399 SSH_PACKET_SF_PENDING_BIT,
400 SSH_PACKET_SF_TRANSMITTING_BIT,
401 SSH_PACKET_SF_TRANSMITTED_BIT,
402 SSH_PACKET_SF_ACKED_BIT,
403 SSH_PACKET_SF_CANCELED_BIT,
404 SSH_PACKET_SF_COMPLETED_BIT,
407 SSH_PACKET_TY_FLUSH_BIT,
408 SSH_PACKET_TY_SEQUENCED_BIT,
409 SSH_PACKET_TY_BLOCKING_BIT,
411 /* mask for state flags */
412 SSH_PACKET_FLAGS_SF_MASK =
413 BIT(SSH_PACKET_SF_LOCKED_BIT)
414 | BIT(SSH_PACKET_SF_QUEUED_BIT)
415 | BIT(SSH_PACKET_SF_PENDING_BIT)
416 | BIT(SSH_PACKET_SF_TRANSMITTING_BIT)
417 | BIT(SSH_PACKET_SF_TRANSMITTED_BIT)
418 | BIT(SSH_PACKET_SF_ACKED_BIT)
419 | BIT(SSH_PACKET_SF_CANCELED_BIT)
420 | BIT(SSH_PACKET_SF_COMPLETED_BIT),
422 /* mask for type flags */
423 SSH_PACKET_FLAGS_TY_MASK =
424 BIT(SSH_PACKET_TY_FLUSH_BIT)
425 | BIT(SSH_PACKET_TY_SEQUENCED_BIT)
426 | BIT(SSH_PACKET_TY_BLOCKING_BIT),
433 * struct ssh_packet_ops - Callback operations for a SSH packet.
434 * @release: Function called when the packet reference count reaches zero.
435 * This callback must be relied upon to ensure that the packet has
436 * left the transport system(s).
437 * @complete: Function called when the packet is completed, either with
438 * success or failure. In case of failure, the reason for the
439 * failure is indicated by the value of the provided status code
440 * argument. This value will be zero in case of success. Note that
441 * a call to this callback does not guarantee that the packet is
442 * not in use by the transport system any more.
444 struct ssh_packet_ops {
445 void (*release)(struct ssh_packet *p);
446 void (*complete)(struct ssh_packet *p, int status);
450 * struct ssh_packet - SSH transport packet.
451 * @ptl: Pointer to the packet transport layer. May be %NULL if the packet
452 * (or enclosing request) has not been submitted yet.
453 * @refcnt: Reference count of the packet.
454 * @priority: Priority of the packet. Must be computed via
455 * SSH_PACKET_PRIORITY(). Must only be accessed while holding the
456 * queue lock after first submission.
457 * @data: Raw message data.
458 * @data.len: Length of the raw message data.
459 * @data.ptr: Pointer to the raw message data buffer.
460 * @state: State and type flags describing current packet state (dynamic)
461 * and type (static). See &enum ssh_packet_flags for possible
463 * @timestamp: Timestamp specifying when the latest transmission of a
464 * currently pending packet has been started. May be %KTIME_MAX
465 * before or in-between transmission attempts. Used for the packet
466 * timeout implementation. Must only be accessed while holding the
467 * pending lock after first submission.
468 * @queue_node: The list node for the packet queue.
469 * @pending_node: The list node for the set of pending packets.
470 * @ops: Packet operations.
486 struct list_head queue_node;
487 struct list_head pending_node;
489 const struct ssh_packet_ops *ops;
492 struct ssh_packet *ssh_packet_get(struct ssh_packet *p);
493 void ssh_packet_put(struct ssh_packet *p);
496 * ssh_packet_set_data() - Set raw message data of packet.
497 * @p: The packet for which the message data should be set.
498 * @ptr: Pointer to the memory holding the message data.
499 * @len: Length of the message data.
501 * Sets the raw message data buffer of the packet to the provided memory. The
502 * memory is not copied. Instead, the caller is responsible for management
503 * (i.e. allocation and deallocation) of the memory. The caller must ensure
504 * that the provided memory is valid and contains a valid SSH message,
505 * starting from the time of submission of the packet until the ``release``
506 * callback has been called. During this time, the memory may not be altered
509 static inline void ssh_packet_set_data(struct ssh_packet *p, u8 *ptr, size_t len)
516 /* -- Request transport layer (rtl). ---------------------------------------- */
518 enum ssh_request_flags {
520 SSH_REQUEST_SF_LOCKED_BIT,
521 SSH_REQUEST_SF_QUEUED_BIT,
522 SSH_REQUEST_SF_PENDING_BIT,
523 SSH_REQUEST_SF_TRANSMITTING_BIT,
524 SSH_REQUEST_SF_TRANSMITTED_BIT,
525 SSH_REQUEST_SF_RSPRCVD_BIT,
526 SSH_REQUEST_SF_CANCELED_BIT,
527 SSH_REQUEST_SF_COMPLETED_BIT,
530 SSH_REQUEST_TY_FLUSH_BIT,
531 SSH_REQUEST_TY_HAS_RESPONSE_BIT,
533 /* mask for state flags */
534 SSH_REQUEST_FLAGS_SF_MASK =
535 BIT(SSH_REQUEST_SF_LOCKED_BIT)
536 | BIT(SSH_REQUEST_SF_QUEUED_BIT)
537 | BIT(SSH_REQUEST_SF_PENDING_BIT)
538 | BIT(SSH_REQUEST_SF_TRANSMITTING_BIT)
539 | BIT(SSH_REQUEST_SF_TRANSMITTED_BIT)
540 | BIT(SSH_REQUEST_SF_RSPRCVD_BIT)
541 | BIT(SSH_REQUEST_SF_CANCELED_BIT)
542 | BIT(SSH_REQUEST_SF_COMPLETED_BIT),
544 /* mask for type flags */
545 SSH_REQUEST_FLAGS_TY_MASK =
546 BIT(SSH_REQUEST_TY_FLUSH_BIT)
547 | BIT(SSH_REQUEST_TY_HAS_RESPONSE_BIT),
554 * struct ssh_request_ops - Callback operations for a SSH request.
555 * @release: Function called when the request's reference count reaches zero.
556 * This callback must be relied upon to ensure that the request has
557 * left the transport systems (both, packet an request systems).
558 * @complete: Function called when the request is completed, either with
559 * success or failure. The command data for the request response
560 * is provided via the &struct ssh_command parameter (``cmd``),
561 * the command payload of the request response via the &struct
562 * ssh_span parameter (``data``).
564 * If the request does not have any response or has not been
565 * completed with success, both ``cmd`` and ``data`` parameters will
566 * be NULL. If the request response does not have any command
567 * payload, the ``data`` span will be an empty (zero-length) span.
569 * In case of failure, the reason for the failure is indicated by
570 * the value of the provided status code argument (``status``). This
571 * value will be zero in case of success and a regular errno
574 * Note that a call to this callback does not guarantee that the
575 * request is not in use by the transport systems any more.
577 struct ssh_request_ops {
578 void (*release)(struct ssh_request *rqst);
579 void (*complete)(struct ssh_request *rqst,
580 const struct ssh_command *cmd,
581 const struct ssam_span *data, int status);
585 * struct ssh_request - SSH transport request.
586 * @packet: The underlying SSH transport packet.
587 * @node: List node for the request queue and pending set.
588 * @state: State and type flags describing current request state (dynamic)
589 * and type (static). See &enum ssh_request_flags for possible
591 * @timestamp: Timestamp specifying when we start waiting on the response of
592 * the request. This is set once the underlying packet has been
593 * completed and may be %KTIME_MAX before that, or when the request
594 * does not expect a response. Used for the request timeout
596 * @ops: Request Operations.
599 struct ssh_packet packet;
600 struct list_head node;
605 const struct ssh_request_ops *ops;
609 * to_ssh_request() - Cast a SSH packet to its enclosing SSH request.
610 * @p: The packet to cast.
612 * Casts the given &struct ssh_packet to its enclosing &struct ssh_request.
613 * The caller is responsible for making sure that the packet is actually
614 * wrapped in a &struct ssh_request.
616 * Return: Returns the &struct ssh_request wrapping the provided packet.
618 static inline struct ssh_request *to_ssh_request(struct ssh_packet *p)
620 return container_of(p, struct ssh_request, packet);
624 * ssh_request_get() - Increment reference count of request.
625 * @r: The request to increment the reference count of.
627 * Increments the reference count of the given request by incrementing the
628 * reference count of the underlying &struct ssh_packet, enclosed in it.
630 * See also ssh_request_put(), ssh_packet_get().
632 * Return: Returns the request provided as input.
634 static inline struct ssh_request *ssh_request_get(struct ssh_request *r)
636 return r ? to_ssh_request(ssh_packet_get(&r->packet)) : NULL;
640 * ssh_request_put() - Decrement reference count of request.
641 * @r: The request to decrement the reference count of.
643 * Decrements the reference count of the given request by decrementing the
644 * reference count of the underlying &struct ssh_packet, enclosed in it. If
645 * the reference count reaches zero, the ``release`` callback specified in the
646 * request's &struct ssh_request_ops, i.e. ``r->ops->release``, will be
649 * See also ssh_request_get(), ssh_packet_put().
651 static inline void ssh_request_put(struct ssh_request *r)
654 ssh_packet_put(&r->packet);
658 * ssh_request_set_data() - Set raw message data of request.
659 * @r: The request for which the message data should be set.
660 * @ptr: Pointer to the memory holding the message data.
661 * @len: Length of the message data.
663 * Sets the raw message data buffer of the underlying packet to the specified
664 * buffer. Does not copy the actual message data, just sets the buffer pointer
665 * and length. Refer to ssh_packet_set_data() for more details.
667 static inline void ssh_request_set_data(struct ssh_request *r, u8 *ptr, size_t len)
669 ssh_packet_set_data(&r->packet, ptr, len);
672 #endif /* _LINUX_SURFACE_AGGREGATOR_SERIAL_HUB_H */