1 /* SPDX-License-Identifier: GPL-2.0+ */
2 /*
3  * Surface System Aggregator Module (SSAM) bus and client-device subsystem.
4  *
5  * Main interface for the surface-aggregator bus, surface-aggregator client
6  * devices, and respective drivers building on top of the SSAM controller.
7  * Provides support for non-platform/non-ACPI SSAM clients via dedicated
8  * subsystem.
9  *
10  * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
11  */
12 
13 #ifndef _LINUX_SURFACE_AGGREGATOR_DEVICE_H
14 #define _LINUX_SURFACE_AGGREGATOR_DEVICE_H
15 
16 #include <linux/device.h>
17 #include <linux/mod_devicetable.h>
18 #include <linux/property.h>
19 #include <linux/types.h>
20 
21 #include <linux/surface_aggregator/controller.h>
22 
23 
24 /* -- Surface System Aggregator Module bus. --------------------------------- */
25 
26 /**
27  * enum ssam_device_domain - SAM device domain.
28  * @SSAM_DOMAIN_VIRTUAL:   Virtual device.
29  * @SSAM_DOMAIN_SERIALHUB: Physical device connected via Surface Serial Hub.
30  */
31 enum ssam_device_domain {
32 	SSAM_DOMAIN_VIRTUAL   = 0x00,
33 	SSAM_DOMAIN_SERIALHUB = 0x01,
34 };
35 
36 /**
37  * enum ssam_virtual_tc - Target categories for the virtual SAM domain.
38  * @SSAM_VIRTUAL_TC_HUB: Device hub category.
39  */
40 enum ssam_virtual_tc {
41 	SSAM_VIRTUAL_TC_HUB = 0x00,
42 };
43 
44 /**
45  * struct ssam_device_uid - Unique identifier for SSAM device.
46  * @domain:   Domain of the device.
47  * @category: Target category of the device.
48  * @target:   Target ID of the device.
49  * @instance: Instance ID of the device.
50  * @function: Sub-function of the device. This field can be used to split a
51  *            single SAM device into multiple virtual subdevices to separate
52  *            different functionality of that device and allow one driver per
53  *            such functionality.
54  */
55 struct ssam_device_uid {
56 	u8 domain;
57 	u8 category;
58 	u8 target;
59 	u8 instance;
60 	u8 function;
61 };
62 
63 /*
64  * Special values for device matching.
65  *
66  * These values are intended to be used with SSAM_DEVICE(), SSAM_VDEV(), and
67  * SSAM_SDEV() exclusively. Specifically, they are used to initialize the
68  * match_flags member of the device ID structure. Do not use them directly
69  * with struct ssam_device_id or struct ssam_device_uid.
70  */
71 #define SSAM_SSH_TID_ANY	0xffff
72 #define SSAM_SSH_IID_ANY	0xffff
73 #define SSAM_SSH_FUN_ANY	0xffff
74 
75 /**
76  * SSAM_DEVICE() - Initialize a &struct ssam_device_id with the given
77  * parameters.
78  * @d:   Domain of the device.
79  * @cat: Target category of the device.
80  * @tid: Target ID of the device.
81  * @iid: Instance ID of the device.
82  * @fun: Sub-function of the device.
83  *
84  * Initializes a &struct ssam_device_id with the given parameters. See &struct
85  * ssam_device_uid for details regarding the parameters. The special values
86  * %SSAM_SSH_TID_ANY, %SSAM_SSH_IID_ANY, and %SSAM_SSH_FUN_ANY can be used to specify that
87  * matching should ignore target ID, instance ID, and/or sub-function,
88  * respectively. This macro initializes the ``match_flags`` field based on the
89  * given parameters.
90  *
91  * Note: The parameters @d and @cat must be valid &u8 values, the parameters
92  * @tid, @iid, and @fun must be either valid &u8 values or %SSAM_SSH_TID_ANY,
93  * %SSAM_SSH_IID_ANY, or %SSAM_SSH_FUN_ANY, respectively. Other non-&u8 values are not
94  * allowed.
95  */
96 #define SSAM_DEVICE(d, cat, tid, iid, fun)					\
97 	.match_flags = (((tid) != SSAM_SSH_TID_ANY) ? SSAM_MATCH_TARGET : 0)	\
98 		     | (((iid) != SSAM_SSH_IID_ANY) ? SSAM_MATCH_INSTANCE : 0)	\
99 		     | (((fun) != SSAM_SSH_FUN_ANY) ? SSAM_MATCH_FUNCTION : 0),	\
100 	.domain   = d,								\
101 	.category = cat,							\
102 	.target   = __builtin_choose_expr((tid) != SSAM_SSH_TID_ANY, (tid), 0),	\
103 	.instance = __builtin_choose_expr((iid) != SSAM_SSH_IID_ANY, (iid), 0),	\
104 	.function = __builtin_choose_expr((fun) != SSAM_SSH_FUN_ANY, (fun), 0)
105 
106 /**
107  * SSAM_VDEV() - Initialize a &struct ssam_device_id as virtual device with
108  * the given parameters.
109  * @cat: Target category of the device.
110  * @tid: Target ID of the device.
111  * @iid: Instance ID of the device.
112  * @fun: Sub-function of the device.
113  *
114  * Initializes a &struct ssam_device_id with the given parameters in the
115  * virtual domain. See &struct ssam_device_uid for details regarding the
116  * parameters. The special values %SSAM_SSH_TID_ANY, %SSAM_SSH_IID_ANY, and
117  * %SSAM_SSH_FUN_ANY can be used to specify that matching should ignore target ID,
118  * instance ID, and/or sub-function, respectively. This macro initializes the
119  * ``match_flags`` field based on the given parameters.
120  *
121  * Note: The parameter @cat must be a valid &u8 value, the parameters @tid,
122  * @iid, and @fun must be either valid &u8 values or %SSAM_SSH_TID_ANY,
123  * %SSAM_SSH_IID_ANY, or %SSAM_SSH_FUN_ANY, respectively. Other non-&u8 values are not
124  * allowed.
125  */
126 #define SSAM_VDEV(cat, tid, iid, fun) \
127 	SSAM_DEVICE(SSAM_DOMAIN_VIRTUAL, SSAM_VIRTUAL_TC_##cat, SSAM_SSH_TID_##tid, iid, fun)
128 
129 /**
130  * SSAM_SDEV() - Initialize a &struct ssam_device_id as physical SSH device
131  * with the given parameters.
132  * @cat: Target category of the device.
133  * @tid: Target ID of the device.
134  * @iid: Instance ID of the device.
135  * @fun: Sub-function of the device.
136  *
137  * Initializes a &struct ssam_device_id with the given parameters in the SSH
138  * domain. See &struct ssam_device_uid for details regarding the parameters.
139  * The special values %SSAM_SSH_TID_ANY, %SSAM_SSH_IID_ANY, and
140  * %SSAM_SSH_FUN_ANY can be used to specify that matching should ignore target
141  * ID, instance ID, and/or sub-function, respectively. This macro initializes
142  * the ``match_flags`` field based on the given parameters.
143  *
144  * Note: The parameter @cat must be a valid &u8 value, the parameters @tid,
145  * @iid, and @fun must be either valid &u8 values or %SSAM_SSH_TID_ANY,
146  * %SSAM_SSH_IID_ANY, or %SSAM_SSH_FUN_ANY, respectively. Other non-&u8 values
147  * are not allowed.
148  */
149 #define SSAM_SDEV(cat, tid, iid, fun) \
150 	SSAM_DEVICE(SSAM_DOMAIN_SERIALHUB, SSAM_SSH_TC_##cat, SSAM_SSH_TID_##tid, iid, fun)
151 
152 /*
153  * enum ssam_device_flags - Flags for SSAM client devices.
154  * @SSAM_DEVICE_HOT_REMOVED_BIT:
155  *	The device has been hot-removed. Further communication with it may time
156  *	out and should be avoided.
157  */
158 enum ssam_device_flags {
159 	SSAM_DEVICE_HOT_REMOVED_BIT = 0,
160 };
161 
162 /**
163  * struct ssam_device - SSAM client device.
164  * @dev:   Driver model representation of the device.
165  * @ctrl:  SSAM controller managing this device.
166  * @uid:   UID identifying the device.
167  * @flags: Device state flags, see &enum ssam_device_flags.
168  */
169 struct ssam_device {
170 	struct device dev;
171 	struct ssam_controller *ctrl;
172 
173 	struct ssam_device_uid uid;
174 
175 	unsigned long flags;
176 };
177 
178 /**
179  * struct ssam_device_driver - SSAM client device driver.
180  * @driver:      Base driver model structure.
181  * @match_table: Match table specifying which devices the driver should bind to.
182  * @probe:       Called when the driver is being bound to a device.
183  * @remove:      Called when the driver is being unbound from the device.
184  */
185 struct ssam_device_driver {
186 	struct device_driver driver;
187 
188 	const struct ssam_device_id *match_table;
189 
190 	int  (*probe)(struct ssam_device *sdev);
191 	void (*remove)(struct ssam_device *sdev);
192 };
193 
194 #ifdef CONFIG_SURFACE_AGGREGATOR_BUS
195 
196 extern struct bus_type ssam_bus_type;
197 extern const struct device_type ssam_device_type;
198 
199 /**
200  * is_ssam_device() - Check if the given device is a SSAM client device.
201  * @d: The device to test the type of.
202  *
203  * Return: Returns %true if the specified device is of type &struct
204  * ssam_device, i.e. the device type points to %ssam_device_type, and %false
205  * otherwise.
206  */
207 static inline bool is_ssam_device(struct device *d)
208 {
209 	return d->type == &ssam_device_type;
210 }
211 
212 #else /* CONFIG_SURFACE_AGGREGATOR_BUS */
213 
214 static inline bool is_ssam_device(struct device *d)
215 {
216 	return false;
217 }
218 
219 #endif /* CONFIG_SURFACE_AGGREGATOR_BUS */
220 
221 /**
222  * to_ssam_device() - Casts the given device to a SSAM client device.
223  * @d: The device to cast.
224  *
225  * Casts the given &struct device to a &struct ssam_device. The caller has to
226  * ensure that the given device is actually enclosed in a &struct ssam_device,
227  * e.g. by calling is_ssam_device().
228  *
229  * Return: Returns a pointer to the &struct ssam_device wrapping the given
230  * device @d.
231  */
232 #define to_ssam_device(d)	container_of_const(d, struct ssam_device, dev)
233 
234 /**
235  * to_ssam_device_driver() - Casts the given device driver to a SSAM client
236  * device driver.
237  * @d: The driver to cast.
238  *
239  * Casts the given &struct device_driver to a &struct ssam_device_driver. The
240  * caller has to ensure that the given driver is actually enclosed in a
241  * &struct ssam_device_driver.
242  *
243  * Return: Returns the pointer to the &struct ssam_device_driver wrapping the
244  * given device driver @d.
245  */
246 static inline
247 struct ssam_device_driver *to_ssam_device_driver(struct device_driver *d)
248 {
249 	return container_of(d, struct ssam_device_driver, driver);
250 }
251 
252 const struct ssam_device_id *ssam_device_id_match(const struct ssam_device_id *table,
253 						  const struct ssam_device_uid uid);
254 
255 const struct ssam_device_id *ssam_device_get_match(const struct ssam_device *dev);
256 
257 const void *ssam_device_get_match_data(const struct ssam_device *dev);
258 
259 struct ssam_device *ssam_device_alloc(struct ssam_controller *ctrl,
260 				      struct ssam_device_uid uid);
261 
262 int ssam_device_add(struct ssam_device *sdev);
263 void ssam_device_remove(struct ssam_device *sdev);
264 
265 /**
266  * ssam_device_mark_hot_removed() - Mark the given device as hot-removed.
267  * @sdev: The device to mark as hot-removed.
268  *
269  * Mark the device as having been hot-removed. This signals drivers using the
270  * device that communication with the device should be avoided and may lead to
271  * timeouts.
272  */
273 static inline void ssam_device_mark_hot_removed(struct ssam_device *sdev)
274 {
275 	dev_dbg(&sdev->dev, "marking device as hot-removed\n");
276 	set_bit(SSAM_DEVICE_HOT_REMOVED_BIT, &sdev->flags);
277 }
278 
279 /**
280  * ssam_device_is_hot_removed() - Check if the given device has been
281  * hot-removed.
282  * @sdev: The device to check.
283  *
284  * Checks if the given device has been marked as hot-removed. See
285  * ssam_device_mark_hot_removed() for more details.
286  *
287  * Return: Returns ``true`` if the device has been marked as hot-removed.
288  */
289 static inline bool ssam_device_is_hot_removed(struct ssam_device *sdev)
290 {
291 	return test_bit(SSAM_DEVICE_HOT_REMOVED_BIT, &sdev->flags);
292 }
293 
294 /**
295  * ssam_device_get() - Increment reference count of SSAM client device.
296  * @sdev: The device to increment the reference count of.
297  *
298  * Increments the reference count of the given SSAM client device by
299  * incrementing the reference count of the enclosed &struct device via
300  * get_device().
301  *
302  * See ssam_device_put() for the counter-part of this function.
303  *
304  * Return: Returns the device provided as input.
305  */
306 static inline struct ssam_device *ssam_device_get(struct ssam_device *sdev)
307 {
308 	return sdev ? to_ssam_device(get_device(&sdev->dev)) : NULL;
309 }
310 
311 /**
312  * ssam_device_put() - Decrement reference count of SSAM client device.
313  * @sdev: The device to decrement the reference count of.
314  *
315  * Decrements the reference count of the given SSAM client device by
316  * decrementing the reference count of the enclosed &struct device via
317  * put_device().
318  *
319  * See ssam_device_get() for the counter-part of this function.
320  */
321 static inline void ssam_device_put(struct ssam_device *sdev)
322 {
323 	if (sdev)
324 		put_device(&sdev->dev);
325 }
326 
327 /**
328  * ssam_device_get_drvdata() - Get driver-data of SSAM client device.
329  * @sdev: The device to get the driver-data from.
330  *
331  * Return: Returns the driver-data of the given device, previously set via
332  * ssam_device_set_drvdata().
333  */
334 static inline void *ssam_device_get_drvdata(struct ssam_device *sdev)
335 {
336 	return dev_get_drvdata(&sdev->dev);
337 }
338 
339 /**
340  * ssam_device_set_drvdata() - Set driver-data of SSAM client device.
341  * @sdev: The device to set the driver-data of.
342  * @data: The data to set the device's driver-data pointer to.
343  */
344 static inline void ssam_device_set_drvdata(struct ssam_device *sdev, void *data)
345 {
346 	dev_set_drvdata(&sdev->dev, data);
347 }
348 
349 int __ssam_device_driver_register(struct ssam_device_driver *d, struct module *o);
350 void ssam_device_driver_unregister(struct ssam_device_driver *d);
351 
352 /**
353  * ssam_device_driver_register() - Register a SSAM client device driver.
354  * @drv: The driver to register.
355  */
356 #define ssam_device_driver_register(drv) \
357 	__ssam_device_driver_register(drv, THIS_MODULE)
358 
359 /**
360  * module_ssam_device_driver() - Helper macro for SSAM device driver
361  * registration.
362  * @drv: The driver managed by this module.
363  *
364  * Helper macro to register a SSAM device driver via module_init() and
365  * module_exit(). This macro may only be used once per module and replaces the
366  * aforementioned definitions.
367  */
368 #define module_ssam_device_driver(drv)			\
369 	module_driver(drv, ssam_device_driver_register,	\
370 		      ssam_device_driver_unregister)
371 
372 
373 /* -- Helpers for controller and hub devices. ------------------------------- */
374 
375 #ifdef CONFIG_SURFACE_AGGREGATOR_BUS
376 
377 int __ssam_register_clients(struct device *parent, struct ssam_controller *ctrl,
378 			    struct fwnode_handle *node);
379 void ssam_remove_clients(struct device *dev);
380 
381 #else /* CONFIG_SURFACE_AGGREGATOR_BUS */
382 
383 static inline int __ssam_register_clients(struct device *parent, struct ssam_controller *ctrl,
384 					  struct fwnode_handle *node)
385 {
386 	return 0;
387 }
388 
389 static inline void ssam_remove_clients(struct device *dev) {}
390 
391 #endif /* CONFIG_SURFACE_AGGREGATOR_BUS */
392 
393 /**
394  * ssam_register_clients() - Register all client devices defined under the
395  * given parent device.
396  * @dev: The parent device under which clients should be registered.
397  * @ctrl: The controller with which client should be registered.
398  *
399  * Register all clients that have via firmware nodes been defined as children
400  * of the given (parent) device. The respective child firmware nodes will be
401  * associated with the correspondingly created child devices.
402  *
403  * The given controller will be used to instantiate the new devices. See
404  * ssam_device_add() for details.
405  *
406  * Return: Returns zero on success, nonzero on failure.
407  */
408 static inline int ssam_register_clients(struct device *dev, struct ssam_controller *ctrl)
409 {
410 	return __ssam_register_clients(dev, ctrl, dev_fwnode(dev));
411 }
412 
413 /**
414  * ssam_device_register_clients() - Register all client devices defined under
415  * the given SSAM parent device.
416  * @sdev: The parent device under which clients should be registered.
417  *
418  * Register all clients that have via firmware nodes been defined as children
419  * of the given (parent) device. The respective child firmware nodes will be
420  * associated with the correspondingly created child devices.
421  *
422  * The controller used by the parent device will be used to instantiate the new
423  * devices. See ssam_device_add() for details.
424  *
425  * Return: Returns zero on success, nonzero on failure.
426  */
427 static inline int ssam_device_register_clients(struct ssam_device *sdev)
428 {
429 	return ssam_register_clients(&sdev->dev, sdev->ctrl);
430 }
431 
432 
433 /* -- Helpers for client-device requests. ----------------------------------- */
434 
435 /**
436  * SSAM_DEFINE_SYNC_REQUEST_CL_N() - Define synchronous client-device SAM
437  * request function with neither argument nor return value.
438  * @name: Name of the generated function.
439  * @spec: Specification (&struct ssam_request_spec_md) defining the request.
440  *
441  * Defines a function executing the synchronous SAM request specified by
442  * @spec, with the request having neither argument nor return value. Device
443  * specifying parameters are not hard-coded, but instead are provided via the
444  * client device, specifically its UID, supplied when calling this function.
445  * The generated function takes care of setting up the request struct, buffer
446  * allocation, as well as execution of the request itself, returning once the
447  * request has been fully completed. The required transport buffer will be
448  * allocated on the stack.
449  *
450  * The generated function is defined as ``static int name(struct ssam_device
451  * *sdev)``, returning the status of the request, which is zero on success and
452  * negative on failure. The ``sdev`` parameter specifies both the target
453  * device of the request and by association the controller via which the
454  * request is sent.
455  *
456  * Refer to ssam_request_do_sync_onstack() for more details on the behavior of
457  * the generated function.
458  */
459 #define SSAM_DEFINE_SYNC_REQUEST_CL_N(name, spec...)			\
460 	SSAM_DEFINE_SYNC_REQUEST_MD_N(__raw_##name, spec)		\
461 	static int name(struct ssam_device *sdev)			\
462 	{								\
463 		return __raw_##name(sdev->ctrl, sdev->uid.target,	\
464 				    sdev->uid.instance);		\
465 	}
466 
467 /**
468  * SSAM_DEFINE_SYNC_REQUEST_CL_W() - Define synchronous client-device SAM
469  * request function with argument.
470  * @name:  Name of the generated function.
471  * @atype: Type of the request's argument.
472  * @spec:  Specification (&struct ssam_request_spec_md) defining the request.
473  *
474  * Defines a function executing the synchronous SAM request specified by
475  * @spec, with the request taking an argument of type @atype and having no
476  * return value. Device specifying parameters are not hard-coded, but instead
477  * are provided via the client device, specifically its UID, supplied when
478  * calling this function. The generated function takes care of setting up the
479  * request struct, buffer allocation, as well as execution of the request
480  * itself, returning once the request has been fully completed. The required
481  * transport buffer will be allocated on the stack.
482  *
483  * The generated function is defined as ``static int name(struct ssam_device
484  * *sdev, const atype *arg)``, returning the status of the request, which is
485  * zero on success and negative on failure. The ``sdev`` parameter specifies
486  * both the target device of the request and by association the controller via
487  * which the request is sent. The request's argument is specified via the
488  * ``arg`` pointer.
489  *
490  * Refer to ssam_request_do_sync_onstack() for more details on the behavior of
491  * the generated function.
492  */
493 #define SSAM_DEFINE_SYNC_REQUEST_CL_W(name, atype, spec...)		\
494 	SSAM_DEFINE_SYNC_REQUEST_MD_W(__raw_##name, atype, spec)	\
495 	static int name(struct ssam_device *sdev, const atype *arg)	\
496 	{								\
497 		return __raw_##name(sdev->ctrl, sdev->uid.target,	\
498 				    sdev->uid.instance, arg);		\
499 	}
500 
501 /**
502  * SSAM_DEFINE_SYNC_REQUEST_CL_R() - Define synchronous client-device SAM
503  * request function with return value.
504  * @name:  Name of the generated function.
505  * @rtype: Type of the request's return value.
506  * @spec:  Specification (&struct ssam_request_spec_md) defining the request.
507  *
508  * Defines a function executing the synchronous SAM request specified by
509  * @spec, with the request taking no argument but having a return value of
510  * type @rtype. Device specifying parameters are not hard-coded, but instead
511  * are provided via the client device, specifically its UID, supplied when
512  * calling this function. The generated function takes care of setting up the
513  * request struct, buffer allocation, as well as execution of the request
514  * itself, returning once the request has been fully completed. The required
515  * transport buffer will be allocated on the stack.
516  *
517  * The generated function is defined as ``static int name(struct ssam_device
518  * *sdev, rtype *ret)``, returning the status of the request, which is zero on
519  * success and negative on failure. The ``sdev`` parameter specifies both the
520  * target device of the request and by association the controller via which
521  * the request is sent. The request's return value is written to the memory
522  * pointed to by the ``ret`` parameter.
523  *
524  * Refer to ssam_request_do_sync_onstack() for more details on the behavior of
525  * the generated function.
526  */
527 #define SSAM_DEFINE_SYNC_REQUEST_CL_R(name, rtype, spec...)		\
528 	SSAM_DEFINE_SYNC_REQUEST_MD_R(__raw_##name, rtype, spec)	\
529 	static int name(struct ssam_device *sdev, rtype *ret)		\
530 	{								\
531 		return __raw_##name(sdev->ctrl, sdev->uid.target,	\
532 				    sdev->uid.instance, ret);		\
533 	}
534 
535 /**
536  * SSAM_DEFINE_SYNC_REQUEST_CL_WR() - Define synchronous client-device SAM
537  * request function with argument and return value.
538  * @name:  Name of the generated function.
539  * @atype: Type of the request's argument.
540  * @rtype: Type of the request's return value.
541  * @spec:  Specification (&struct ssam_request_spec_md) defining the request.
542  *
543  * Defines a function executing the synchronous SAM request specified by @spec,
544  * with the request taking an argument of type @atype and having a return value
545  * of type @rtype. Device specifying parameters are not hard-coded, but instead
546  * are provided via the client device, specifically its UID, supplied when
547  * calling this function. The generated function takes care of setting up the
548  * request struct, buffer allocation, as well as execution of the request
549  * itself, returning once the request has been fully completed. The required
550  * transport buffer will be allocated on the stack.
551  *
552  * The generated function is defined as ``static int name(struct ssam_device
553  * *sdev, const atype *arg, rtype *ret)``, returning the status of the request,
554  * which is zero on success and negative on failure. The ``sdev`` parameter
555  * specifies both the target device of the request and by association the
556  * controller via which the request is sent. The request's argument is
557  * specified via the ``arg`` pointer. The request's return value is written to
558  * the memory pointed to by the ``ret`` parameter.
559  *
560  * Refer to ssam_request_do_sync_onstack() for more details on the behavior of
561  * the generated function.
562  */
563 #define SSAM_DEFINE_SYNC_REQUEST_CL_WR(name, atype, rtype, spec...)		\
564 	SSAM_DEFINE_SYNC_REQUEST_MD_WR(__raw_##name, atype, rtype, spec)	\
565 	static int name(struct ssam_device *sdev, const atype *arg, rtype *ret)	\
566 	{									\
567 		return __raw_##name(sdev->ctrl, sdev->uid.target,		\
568 				    sdev->uid.instance, arg, ret);		\
569 	}
570 
571 
572 /* -- Helpers for client-device notifiers. ---------------------------------- */
573 
574 /**
575  * ssam_device_notifier_register() - Register an event notifier for the
576  * specified client device.
577  * @sdev: The device the notifier should be registered on.
578  * @n:    The event notifier to register.
579  *
580  * Register an event notifier. Increment the usage counter of the associated
581  * SAM event if the notifier is not marked as an observer. If the event is not
582  * marked as an observer and is currently not enabled, it will be enabled
583  * during this call. If the notifier is marked as an observer, no attempt will
584  * be made at enabling any event and no reference count will be modified.
585  *
586  * Notifiers marked as observers do not need to be associated with one specific
587  * event, i.e. as long as no event matching is performed, only the event target
588  * category needs to be set.
589  *
590  * Return: Returns zero on success, %-ENOSPC if there have already been
591  * %INT_MAX notifiers for the event ID/type associated with the notifier block
592  * registered, %-ENOMEM if the corresponding event entry could not be
593  * allocated, %-ENODEV if the device is marked as hot-removed. If this is the
594  * first time that a notifier block is registered for the specific associated
595  * event, returns the status of the event-enable EC-command.
596  */
597 static inline int ssam_device_notifier_register(struct ssam_device *sdev,
598 						struct ssam_event_notifier *n)
599 {
600 	/*
601 	 * Note that this check does not provide any guarantees whatsoever as
602 	 * hot-removal could happen at any point and we can't protect against
603 	 * it. Nevertheless, if we can detect hot-removal, bail early to avoid
604 	 * communication timeouts.
605 	 */
606 	if (ssam_device_is_hot_removed(sdev))
607 		return -ENODEV;
608 
609 	return ssam_notifier_register(sdev->ctrl, n);
610 }
611 
612 /**
613  * ssam_device_notifier_unregister() - Unregister an event notifier for the
614  * specified client device.
615  * @sdev: The device the notifier has been registered on.
616  * @n:    The event notifier to unregister.
617  *
618  * Unregister an event notifier. Decrement the usage counter of the associated
619  * SAM event if the notifier is not marked as an observer. If the usage counter
620  * reaches zero, the event will be disabled.
621  *
622  * In case the device has been marked as hot-removed, the event will not be
623  * disabled on the EC, as in those cases any attempt at doing so may time out.
624  *
625  * Return: Returns zero on success, %-ENOENT if the given notifier block has
626  * not been registered on the controller. If the given notifier block was the
627  * last one associated with its specific event, returns the status of the
628  * event-disable EC-command.
629  */
630 static inline int ssam_device_notifier_unregister(struct ssam_device *sdev,
631 						  struct ssam_event_notifier *n)
632 {
633 	return __ssam_notifier_unregister(sdev->ctrl, n,
634 					  !ssam_device_is_hot_removed(sdev));
635 }
636 
637 #endif /* _LINUX_SURFACE_AGGREGATOR_DEVICE_H */
638