1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Surface Book (gen. 2 and later) detachment system (DTX) driver.
4  *
5  * Provides a user-space interface to properly handle clipboard/tablet
6  * (containing screen and processor) detachment from the base of the device
7  * (containing the keyboard and optionally a discrete GPU). Allows to
8  * acknowledge (to speed things up), abort (e.g. in case the dGPU is still in
9  * use), or request detachment via user-space.
10  *
11  * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
12  */
13 
14 #include <linux/fs.h>
15 #include <linux/input.h>
16 #include <linux/ioctl.h>
17 #include <linux/kernel.h>
18 #include <linux/kfifo.h>
19 #include <linux/kref.h>
20 #include <linux/miscdevice.h>
21 #include <linux/module.h>
22 #include <linux/mutex.h>
23 #include <linux/platform_device.h>
24 #include <linux/poll.h>
25 #include <linux/rwsem.h>
26 #include <linux/slab.h>
27 #include <linux/workqueue.h>
28 
29 #include <linux/surface_aggregator/controller.h>
30 #include <linux/surface_aggregator/device.h>
31 #include <linux/surface_aggregator/dtx.h>
32 
33 
34 /* -- SSAM interface. ------------------------------------------------------- */
35 
36 enum sam_event_cid_bas {
37 	SAM_EVENT_CID_DTX_CONNECTION			= 0x0c,
38 	SAM_EVENT_CID_DTX_REQUEST			= 0x0e,
39 	SAM_EVENT_CID_DTX_CANCEL			= 0x0f,
40 	SAM_EVENT_CID_DTX_LATCH_STATUS			= 0x11,
41 };
42 
43 enum ssam_bas_base_state {
44 	SSAM_BAS_BASE_STATE_DETACH_SUCCESS		= 0x00,
45 	SSAM_BAS_BASE_STATE_ATTACHED			= 0x01,
46 	SSAM_BAS_BASE_STATE_NOT_FEASIBLE		= 0x02,
47 };
48 
49 enum ssam_bas_latch_status {
50 	SSAM_BAS_LATCH_STATUS_CLOSED			= 0x00,
51 	SSAM_BAS_LATCH_STATUS_OPENED			= 0x01,
52 	SSAM_BAS_LATCH_STATUS_FAILED_TO_OPEN		= 0x02,
53 	SSAM_BAS_LATCH_STATUS_FAILED_TO_REMAIN_OPEN	= 0x03,
54 	SSAM_BAS_LATCH_STATUS_FAILED_TO_CLOSE		= 0x04,
55 };
56 
57 enum ssam_bas_cancel_reason {
58 	SSAM_BAS_CANCEL_REASON_NOT_FEASIBLE		= 0x00,  /* Low battery. */
59 	SSAM_BAS_CANCEL_REASON_TIMEOUT			= 0x02,
60 	SSAM_BAS_CANCEL_REASON_FAILED_TO_OPEN		= 0x03,
61 	SSAM_BAS_CANCEL_REASON_FAILED_TO_REMAIN_OPEN	= 0x04,
62 	SSAM_BAS_CANCEL_REASON_FAILED_TO_CLOSE		= 0x05,
63 };
64 
65 struct ssam_bas_base_info {
66 	u8 state;
67 	u8 base_id;
68 } __packed;
69 
70 static_assert(sizeof(struct ssam_bas_base_info) == 2);
71 
72 SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_lock, {
73 	.target_category = SSAM_SSH_TC_BAS,
74 	.target_id       = 0x01,
75 	.command_id      = 0x06,
76 	.instance_id     = 0x00,
77 });
78 
79 SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_unlock, {
80 	.target_category = SSAM_SSH_TC_BAS,
81 	.target_id       = 0x01,
82 	.command_id      = 0x07,
83 	.instance_id     = 0x00,
84 });
85 
86 SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_request, {
87 	.target_category = SSAM_SSH_TC_BAS,
88 	.target_id       = 0x01,
89 	.command_id      = 0x08,
90 	.instance_id     = 0x00,
91 });
92 
93 SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_confirm, {
94 	.target_category = SSAM_SSH_TC_BAS,
95 	.target_id       = 0x01,
96 	.command_id      = 0x09,
97 	.instance_id     = 0x00,
98 });
99 
100 SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_heartbeat, {
101 	.target_category = SSAM_SSH_TC_BAS,
102 	.target_id       = 0x01,
103 	.command_id      = 0x0a,
104 	.instance_id     = 0x00,
105 });
106 
107 SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_cancel, {
108 	.target_category = SSAM_SSH_TC_BAS,
109 	.target_id       = 0x01,
110 	.command_id      = 0x0b,
111 	.instance_id     = 0x00,
112 });
113 
114 SSAM_DEFINE_SYNC_REQUEST_R(ssam_bas_get_base, struct ssam_bas_base_info, {
115 	.target_category = SSAM_SSH_TC_BAS,
116 	.target_id       = 0x01,
117 	.command_id      = 0x0c,
118 	.instance_id     = 0x00,
119 });
120 
121 SSAM_DEFINE_SYNC_REQUEST_R(ssam_bas_get_device_mode, u8, {
122 	.target_category = SSAM_SSH_TC_BAS,
123 	.target_id       = 0x01,
124 	.command_id      = 0x0d,
125 	.instance_id     = 0x00,
126 });
127 
128 SSAM_DEFINE_SYNC_REQUEST_R(ssam_bas_get_latch_status, u8, {
129 	.target_category = SSAM_SSH_TC_BAS,
130 	.target_id       = 0x01,
131 	.command_id      = 0x11,
132 	.instance_id     = 0x00,
133 });
134 
135 
136 /* -- Main structures. ------------------------------------------------------ */
137 
138 enum sdtx_device_state {
139 	SDTX_DEVICE_SHUTDOWN_BIT    = BIT(0),
140 	SDTX_DEVICE_DIRTY_BASE_BIT  = BIT(1),
141 	SDTX_DEVICE_DIRTY_MODE_BIT  = BIT(2),
142 	SDTX_DEVICE_DIRTY_LATCH_BIT = BIT(3),
143 };
144 
145 struct sdtx_device {
146 	struct kref kref;
147 	struct rw_semaphore lock;         /* Guards device and controller reference. */
148 
149 	struct device *dev;
150 	struct ssam_controller *ctrl;
151 	unsigned long flags;
152 
153 	struct miscdevice mdev;
154 	wait_queue_head_t waitq;
155 	struct mutex write_lock;          /* Guards order of events/notifications. */
156 	struct rw_semaphore client_lock;  /* Guards client list.                   */
157 	struct list_head client_list;
158 
159 	struct delayed_work state_work;
160 	struct {
161 		struct ssam_bas_base_info base;
162 		u8 device_mode;
163 		u8 latch_status;
164 	} state;
165 
166 	struct delayed_work mode_work;
167 	struct input_dev *mode_switch;
168 
169 	struct ssam_event_notifier notif;
170 };
171 
172 enum sdtx_client_state {
173 	SDTX_CLIENT_EVENTS_ENABLED_BIT = BIT(0),
174 };
175 
176 struct sdtx_client {
177 	struct sdtx_device *ddev;
178 	struct list_head node;
179 	unsigned long flags;
180 
181 	struct fasync_struct *fasync;
182 
183 	struct mutex read_lock;           /* Guards FIFO buffer read access. */
184 	DECLARE_KFIFO(buffer, u8, 512);
185 };
186 
187 static void __sdtx_device_release(struct kref *kref)
188 {
189 	struct sdtx_device *ddev = container_of(kref, struct sdtx_device, kref);
190 
191 	mutex_destroy(&ddev->write_lock);
192 	kfree(ddev);
193 }
194 
195 static struct sdtx_device *sdtx_device_get(struct sdtx_device *ddev)
196 {
197 	if (ddev)
198 		kref_get(&ddev->kref);
199 
200 	return ddev;
201 }
202 
203 static void sdtx_device_put(struct sdtx_device *ddev)
204 {
205 	if (ddev)
206 		kref_put(&ddev->kref, __sdtx_device_release);
207 }
208 
209 
210 /* -- Firmware value translations. ------------------------------------------ */
211 
212 static u16 sdtx_translate_base_state(struct sdtx_device *ddev, u8 state)
213 {
214 	switch (state) {
215 	case SSAM_BAS_BASE_STATE_ATTACHED:
216 		return SDTX_BASE_ATTACHED;
217 
218 	case SSAM_BAS_BASE_STATE_DETACH_SUCCESS:
219 		return SDTX_BASE_DETACHED;
220 
221 	case SSAM_BAS_BASE_STATE_NOT_FEASIBLE:
222 		return SDTX_DETACH_NOT_FEASIBLE;
223 
224 	default:
225 		dev_err(ddev->dev, "unknown base state: %#04x\n", state);
226 		return SDTX_UNKNOWN(state);
227 	}
228 }
229 
230 static u16 sdtx_translate_latch_status(struct sdtx_device *ddev, u8 status)
231 {
232 	switch (status) {
233 	case SSAM_BAS_LATCH_STATUS_CLOSED:
234 		return SDTX_LATCH_CLOSED;
235 
236 	case SSAM_BAS_LATCH_STATUS_OPENED:
237 		return SDTX_LATCH_OPENED;
238 
239 	case SSAM_BAS_LATCH_STATUS_FAILED_TO_OPEN:
240 		return SDTX_ERR_FAILED_TO_OPEN;
241 
242 	case SSAM_BAS_LATCH_STATUS_FAILED_TO_REMAIN_OPEN:
243 		return SDTX_ERR_FAILED_TO_REMAIN_OPEN;
244 
245 	case SSAM_BAS_LATCH_STATUS_FAILED_TO_CLOSE:
246 		return SDTX_ERR_FAILED_TO_CLOSE;
247 
248 	default:
249 		dev_err(ddev->dev, "unknown latch status: %#04x\n", status);
250 		return SDTX_UNKNOWN(status);
251 	}
252 }
253 
254 static u16 sdtx_translate_cancel_reason(struct sdtx_device *ddev, u8 reason)
255 {
256 	switch (reason) {
257 	case SSAM_BAS_CANCEL_REASON_NOT_FEASIBLE:
258 		return SDTX_DETACH_NOT_FEASIBLE;
259 
260 	case SSAM_BAS_CANCEL_REASON_TIMEOUT:
261 		return SDTX_DETACH_TIMEDOUT;
262 
263 	case SSAM_BAS_CANCEL_REASON_FAILED_TO_OPEN:
264 		return SDTX_ERR_FAILED_TO_OPEN;
265 
266 	case SSAM_BAS_CANCEL_REASON_FAILED_TO_REMAIN_OPEN:
267 		return SDTX_ERR_FAILED_TO_REMAIN_OPEN;
268 
269 	case SSAM_BAS_CANCEL_REASON_FAILED_TO_CLOSE:
270 		return SDTX_ERR_FAILED_TO_CLOSE;
271 
272 	default:
273 		dev_err(ddev->dev, "unknown cancel reason: %#04x\n", reason);
274 		return SDTX_UNKNOWN(reason);
275 	}
276 }
277 
278 
279 /* -- IOCTLs. --------------------------------------------------------------- */
280 
281 static int sdtx_ioctl_get_base_info(struct sdtx_device *ddev,
282 				    struct sdtx_base_info __user *buf)
283 {
284 	struct ssam_bas_base_info raw;
285 	struct sdtx_base_info info;
286 	int status;
287 
288 	lockdep_assert_held_read(&ddev->lock);
289 
290 	status = ssam_retry(ssam_bas_get_base, ddev->ctrl, &raw);
291 	if (status < 0)
292 		return status;
293 
294 	info.state = sdtx_translate_base_state(ddev, raw.state);
295 	info.base_id = SDTX_BASE_TYPE_SSH(raw.base_id);
296 
297 	if (copy_to_user(buf, &info, sizeof(info)))
298 		return -EFAULT;
299 
300 	return 0;
301 }
302 
303 static int sdtx_ioctl_get_device_mode(struct sdtx_device *ddev, u16 __user *buf)
304 {
305 	u8 mode;
306 	int status;
307 
308 	lockdep_assert_held_read(&ddev->lock);
309 
310 	status = ssam_retry(ssam_bas_get_device_mode, ddev->ctrl, &mode);
311 	if (status < 0)
312 		return status;
313 
314 	return put_user(mode, buf);
315 }
316 
317 static int sdtx_ioctl_get_latch_status(struct sdtx_device *ddev, u16 __user *buf)
318 {
319 	u8 latch;
320 	int status;
321 
322 	lockdep_assert_held_read(&ddev->lock);
323 
324 	status = ssam_retry(ssam_bas_get_latch_status, ddev->ctrl, &latch);
325 	if (status < 0)
326 		return status;
327 
328 	return put_user(sdtx_translate_latch_status(ddev, latch), buf);
329 }
330 
331 static long __surface_dtx_ioctl(struct sdtx_client *client, unsigned int cmd, unsigned long arg)
332 {
333 	struct sdtx_device *ddev = client->ddev;
334 
335 	lockdep_assert_held_read(&ddev->lock);
336 
337 	switch (cmd) {
338 	case SDTX_IOCTL_EVENTS_ENABLE:
339 		set_bit(SDTX_CLIENT_EVENTS_ENABLED_BIT, &client->flags);
340 		return 0;
341 
342 	case SDTX_IOCTL_EVENTS_DISABLE:
343 		clear_bit(SDTX_CLIENT_EVENTS_ENABLED_BIT, &client->flags);
344 		return 0;
345 
346 	case SDTX_IOCTL_LATCH_LOCK:
347 		return ssam_retry(ssam_bas_latch_lock, ddev->ctrl);
348 
349 	case SDTX_IOCTL_LATCH_UNLOCK:
350 		return ssam_retry(ssam_bas_latch_unlock, ddev->ctrl);
351 
352 	case SDTX_IOCTL_LATCH_REQUEST:
353 		return ssam_retry(ssam_bas_latch_request, ddev->ctrl);
354 
355 	case SDTX_IOCTL_LATCH_CONFIRM:
356 		return ssam_retry(ssam_bas_latch_confirm, ddev->ctrl);
357 
358 	case SDTX_IOCTL_LATCH_HEARTBEAT:
359 		return ssam_retry(ssam_bas_latch_heartbeat, ddev->ctrl);
360 
361 	case SDTX_IOCTL_LATCH_CANCEL:
362 		return ssam_retry(ssam_bas_latch_cancel, ddev->ctrl);
363 
364 	case SDTX_IOCTL_GET_BASE_INFO:
365 		return sdtx_ioctl_get_base_info(ddev, (struct sdtx_base_info __user *)arg);
366 
367 	case SDTX_IOCTL_GET_DEVICE_MODE:
368 		return sdtx_ioctl_get_device_mode(ddev, (u16 __user *)arg);
369 
370 	case SDTX_IOCTL_GET_LATCH_STATUS:
371 		return sdtx_ioctl_get_latch_status(ddev, (u16 __user *)arg);
372 
373 	default:
374 		return -EINVAL;
375 	}
376 }
377 
378 static long surface_dtx_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
379 {
380 	struct sdtx_client *client = file->private_data;
381 	long status;
382 
383 	if (down_read_killable(&client->ddev->lock))
384 		return -ERESTARTSYS;
385 
386 	if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &client->ddev->flags)) {
387 		up_read(&client->ddev->lock);
388 		return -ENODEV;
389 	}
390 
391 	status = __surface_dtx_ioctl(client, cmd, arg);
392 
393 	up_read(&client->ddev->lock);
394 	return status;
395 }
396 
397 
398 /* -- File operations. ------------------------------------------------------ */
399 
400 static int surface_dtx_open(struct inode *inode, struct file *file)
401 {
402 	struct sdtx_device *ddev = container_of(file->private_data, struct sdtx_device, mdev);
403 	struct sdtx_client *client;
404 
405 	/* Initialize client. */
406 	client = kzalloc(sizeof(*client), GFP_KERNEL);
407 	if (!client)
408 		return -ENOMEM;
409 
410 	client->ddev = sdtx_device_get(ddev);
411 
412 	INIT_LIST_HEAD(&client->node);
413 
414 	mutex_init(&client->read_lock);
415 	INIT_KFIFO(client->buffer);
416 
417 	file->private_data = client;
418 
419 	/* Attach client. */
420 	down_write(&ddev->client_lock);
421 
422 	/*
423 	 * Do not add a new client if the device has been shut down. Note that
424 	 * it's enough to hold the client_lock here as, during shutdown, we
425 	 * only acquire that lock and remove clients after marking the device
426 	 * as shut down.
427 	 */
428 	if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &ddev->flags)) {
429 		up_write(&ddev->client_lock);
430 		mutex_destroy(&client->read_lock);
431 		sdtx_device_put(client->ddev);
432 		kfree(client);
433 		return -ENODEV;
434 	}
435 
436 	list_add_tail(&client->node, &ddev->client_list);
437 	up_write(&ddev->client_lock);
438 
439 	stream_open(inode, file);
440 	return 0;
441 }
442 
443 static int surface_dtx_release(struct inode *inode, struct file *file)
444 {
445 	struct sdtx_client *client = file->private_data;
446 
447 	/* Detach client. */
448 	down_write(&client->ddev->client_lock);
449 	list_del(&client->node);
450 	up_write(&client->ddev->client_lock);
451 
452 	/* Free client. */
453 	sdtx_device_put(client->ddev);
454 	mutex_destroy(&client->read_lock);
455 	kfree(client);
456 
457 	return 0;
458 }
459 
460 static ssize_t surface_dtx_read(struct file *file, char __user *buf, size_t count, loff_t *offs)
461 {
462 	struct sdtx_client *client = file->private_data;
463 	struct sdtx_device *ddev = client->ddev;
464 	unsigned int copied;
465 	int status = 0;
466 
467 	if (down_read_killable(&ddev->lock))
468 		return -ERESTARTSYS;
469 
470 	/* Make sure we're not shut down. */
471 	if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &ddev->flags)) {
472 		up_read(&ddev->lock);
473 		return -ENODEV;
474 	}
475 
476 	do {
477 		/* Check availability, wait if necessary. */
478 		if (kfifo_is_empty(&client->buffer)) {
479 			up_read(&ddev->lock);
480 
481 			if (file->f_flags & O_NONBLOCK)
482 				return -EAGAIN;
483 
484 			status = wait_event_interruptible(ddev->waitq,
485 							  !kfifo_is_empty(&client->buffer) ||
486 							  test_bit(SDTX_DEVICE_SHUTDOWN_BIT,
487 								   &ddev->flags));
488 			if (status < 0)
489 				return status;
490 
491 			if (down_read_killable(&ddev->lock))
492 				return -ERESTARTSYS;
493 
494 			/* Need to check that we're not shut down again. */
495 			if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &ddev->flags)) {
496 				up_read(&ddev->lock);
497 				return -ENODEV;
498 			}
499 		}
500 
501 		/* Try to read from FIFO. */
502 		if (mutex_lock_interruptible(&client->read_lock)) {
503 			up_read(&ddev->lock);
504 			return -ERESTARTSYS;
505 		}
506 
507 		status = kfifo_to_user(&client->buffer, buf, count, &copied);
508 		mutex_unlock(&client->read_lock);
509 
510 		if (status < 0) {
511 			up_read(&ddev->lock);
512 			return status;
513 		}
514 
515 		/* We might not have gotten anything, check this here. */
516 		if (copied == 0 && (file->f_flags & O_NONBLOCK)) {
517 			up_read(&ddev->lock);
518 			return -EAGAIN;
519 		}
520 	} while (copied == 0);
521 
522 	up_read(&ddev->lock);
523 	return copied;
524 }
525 
526 static __poll_t surface_dtx_poll(struct file *file, struct poll_table_struct *pt)
527 {
528 	struct sdtx_client *client = file->private_data;
529 	__poll_t events = 0;
530 
531 	if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &client->ddev->flags))
532 		return EPOLLHUP | EPOLLERR;
533 
534 	poll_wait(file, &client->ddev->waitq, pt);
535 
536 	if (!kfifo_is_empty(&client->buffer))
537 		events |= EPOLLIN | EPOLLRDNORM;
538 
539 	return events;
540 }
541 
542 static int surface_dtx_fasync(int fd, struct file *file, int on)
543 {
544 	struct sdtx_client *client = file->private_data;
545 
546 	return fasync_helper(fd, file, on, &client->fasync);
547 }
548 
549 static const struct file_operations surface_dtx_fops = {
550 	.owner          = THIS_MODULE,
551 	.open           = surface_dtx_open,
552 	.release        = surface_dtx_release,
553 	.read           = surface_dtx_read,
554 	.poll           = surface_dtx_poll,
555 	.fasync         = surface_dtx_fasync,
556 	.unlocked_ioctl = surface_dtx_ioctl,
557 	.compat_ioctl   = surface_dtx_ioctl,
558 	.llseek         = no_llseek,
559 };
560 
561 
562 /* -- Event handling/forwarding. -------------------------------------------- */
563 
564 /*
565  * The device operation mode is not immediately updated on the EC when the
566  * base has been connected, i.e. querying the device mode inside the
567  * connection event callback yields an outdated value. Thus, we can only
568  * determine the new tablet-mode switch and device mode values after some
569  * time.
570  *
571  * These delays have been chosen by experimenting. We first delay on connect
572  * events, then check and validate the device mode against the base state and
573  * if invalid delay again by the "recheck" delay.
574  */
575 #define SDTX_DEVICE_MODE_DELAY_CONNECT	msecs_to_jiffies(100)
576 #define SDTX_DEVICE_MODE_DELAY_RECHECK	msecs_to_jiffies(100)
577 
578 struct sdtx_status_event {
579 	struct sdtx_event e;
580 	__u16 v;
581 } __packed;
582 
583 struct sdtx_base_info_event {
584 	struct sdtx_event e;
585 	struct sdtx_base_info v;
586 } __packed;
587 
588 union sdtx_generic_event {
589 	struct sdtx_event common;
590 	struct sdtx_status_event status;
591 	struct sdtx_base_info_event base;
592 };
593 
594 static void sdtx_update_device_mode(struct sdtx_device *ddev, unsigned long delay);
595 
596 /* Must be executed with ddev->write_lock held. */
597 static void sdtx_push_event(struct sdtx_device *ddev, struct sdtx_event *evt)
598 {
599 	const size_t len = sizeof(struct sdtx_event) + evt->length;
600 	struct sdtx_client *client;
601 
602 	lockdep_assert_held(&ddev->write_lock);
603 
604 	down_read(&ddev->client_lock);
605 	list_for_each_entry(client, &ddev->client_list, node) {
606 		if (!test_bit(SDTX_CLIENT_EVENTS_ENABLED_BIT, &client->flags))
607 			continue;
608 
609 		if (likely(kfifo_avail(&client->buffer) >= len))
610 			kfifo_in(&client->buffer, (const u8 *)evt, len);
611 		else
612 			dev_warn(ddev->dev, "event buffer overrun\n");
613 
614 		kill_fasync(&client->fasync, SIGIO, POLL_IN);
615 	}
616 	up_read(&ddev->client_lock);
617 
618 	wake_up_interruptible(&ddev->waitq);
619 }
620 
621 static u32 sdtx_notifier(struct ssam_event_notifier *nf, const struct ssam_event *in)
622 {
623 	struct sdtx_device *ddev = container_of(nf, struct sdtx_device, notif);
624 	union sdtx_generic_event event;
625 	size_t len;
626 
627 	/* Validate event payload length. */
628 	switch (in->command_id) {
629 	case SAM_EVENT_CID_DTX_CONNECTION:
630 		len = 2 * sizeof(u8);
631 		break;
632 
633 	case SAM_EVENT_CID_DTX_REQUEST:
634 		len = 0;
635 		break;
636 
637 	case SAM_EVENT_CID_DTX_CANCEL:
638 		len = sizeof(u8);
639 		break;
640 
641 	case SAM_EVENT_CID_DTX_LATCH_STATUS:
642 		len = sizeof(u8);
643 		break;
644 
645 	default:
646 		return 0;
647 	}
648 
649 	if (in->length != len) {
650 		dev_err(ddev->dev,
651 			"unexpected payload size for event %#04x: got %u, expected %zu\n",
652 			in->command_id, in->length, len);
653 		return 0;
654 	}
655 
656 	mutex_lock(&ddev->write_lock);
657 
658 	/* Translate event. */
659 	switch (in->command_id) {
660 	case SAM_EVENT_CID_DTX_CONNECTION:
661 		clear_bit(SDTX_DEVICE_DIRTY_BASE_BIT, &ddev->flags);
662 
663 		/* If state has not changed: do not send new event. */
664 		if (ddev->state.base.state == in->data[0] &&
665 		    ddev->state.base.base_id == in->data[1])
666 			goto out;
667 
668 		ddev->state.base.state = in->data[0];
669 		ddev->state.base.base_id = in->data[1];
670 
671 		event.base.e.length = sizeof(struct sdtx_base_info);
672 		event.base.e.code = SDTX_EVENT_BASE_CONNECTION;
673 		event.base.v.state = sdtx_translate_base_state(ddev, in->data[0]);
674 		event.base.v.base_id = SDTX_BASE_TYPE_SSH(in->data[1]);
675 		break;
676 
677 	case SAM_EVENT_CID_DTX_REQUEST:
678 		event.common.code = SDTX_EVENT_REQUEST;
679 		event.common.length = 0;
680 		break;
681 
682 	case SAM_EVENT_CID_DTX_CANCEL:
683 		event.status.e.length = sizeof(u16);
684 		event.status.e.code = SDTX_EVENT_CANCEL;
685 		event.status.v = sdtx_translate_cancel_reason(ddev, in->data[0]);
686 		break;
687 
688 	case SAM_EVENT_CID_DTX_LATCH_STATUS:
689 		clear_bit(SDTX_DEVICE_DIRTY_LATCH_BIT, &ddev->flags);
690 
691 		/* If state has not changed: do not send new event. */
692 		if (ddev->state.latch_status == in->data[0])
693 			goto out;
694 
695 		ddev->state.latch_status = in->data[0];
696 
697 		event.status.e.length = sizeof(u16);
698 		event.status.e.code = SDTX_EVENT_LATCH_STATUS;
699 		event.status.v = sdtx_translate_latch_status(ddev, in->data[0]);
700 		break;
701 	}
702 
703 	sdtx_push_event(ddev, &event.common);
704 
705 	/* Update device mode on base connection change. */
706 	if (in->command_id == SAM_EVENT_CID_DTX_CONNECTION) {
707 		unsigned long delay;
708 
709 		delay = in->data[0] ? SDTX_DEVICE_MODE_DELAY_CONNECT : 0;
710 		sdtx_update_device_mode(ddev, delay);
711 	}
712 
713 out:
714 	mutex_unlock(&ddev->write_lock);
715 	return SSAM_NOTIF_HANDLED;
716 }
717 
718 
719 /* -- State update functions. ----------------------------------------------- */
720 
721 static bool sdtx_device_mode_invalid(u8 mode, u8 base_state)
722 {
723 	return ((base_state == SSAM_BAS_BASE_STATE_ATTACHED) &&
724 		(mode == SDTX_DEVICE_MODE_TABLET)) ||
725 	       ((base_state == SSAM_BAS_BASE_STATE_DETACH_SUCCESS) &&
726 		(mode != SDTX_DEVICE_MODE_TABLET));
727 }
728 
729 static void sdtx_device_mode_workfn(struct work_struct *work)
730 {
731 	struct sdtx_device *ddev = container_of(work, struct sdtx_device, mode_work.work);
732 	struct sdtx_status_event event;
733 	struct ssam_bas_base_info base;
734 	int status, tablet;
735 	u8 mode;
736 
737 	/* Get operation mode. */
738 	status = ssam_retry(ssam_bas_get_device_mode, ddev->ctrl, &mode);
739 	if (status) {
740 		dev_err(ddev->dev, "failed to get device mode: %d\n", status);
741 		return;
742 	}
743 
744 	/* Get base info. */
745 	status = ssam_retry(ssam_bas_get_base, ddev->ctrl, &base);
746 	if (status) {
747 		dev_err(ddev->dev, "failed to get base info: %d\n", status);
748 		return;
749 	}
750 
751 	/*
752 	 * In some cases (specifically when attaching the base), the device
753 	 * mode isn't updated right away. Thus we check if the device mode
754 	 * makes sense for the given base state and try again later if it
755 	 * doesn't.
756 	 */
757 	if (sdtx_device_mode_invalid(mode, base.state)) {
758 		dev_dbg(ddev->dev, "device mode is invalid, trying again\n");
759 		sdtx_update_device_mode(ddev, SDTX_DEVICE_MODE_DELAY_RECHECK);
760 		return;
761 	}
762 
763 	mutex_lock(&ddev->write_lock);
764 	clear_bit(SDTX_DEVICE_DIRTY_MODE_BIT, &ddev->flags);
765 
766 	/* Avoid sending duplicate device-mode events. */
767 	if (ddev->state.device_mode == mode) {
768 		mutex_unlock(&ddev->write_lock);
769 		return;
770 	}
771 
772 	ddev->state.device_mode = mode;
773 
774 	event.e.length = sizeof(u16);
775 	event.e.code = SDTX_EVENT_DEVICE_MODE;
776 	event.v = mode;
777 
778 	sdtx_push_event(ddev, &event.e);
779 
780 	/* Send SW_TABLET_MODE event. */
781 	tablet = mode != SDTX_DEVICE_MODE_LAPTOP;
782 	input_report_switch(ddev->mode_switch, SW_TABLET_MODE, tablet);
783 	input_sync(ddev->mode_switch);
784 
785 	mutex_unlock(&ddev->write_lock);
786 }
787 
788 static void sdtx_update_device_mode(struct sdtx_device *ddev, unsigned long delay)
789 {
790 	schedule_delayed_work(&ddev->mode_work, delay);
791 }
792 
793 /* Must be executed with ddev->write_lock held. */
794 static void __sdtx_device_state_update_base(struct sdtx_device *ddev,
795 					    struct ssam_bas_base_info info)
796 {
797 	struct sdtx_base_info_event event;
798 
799 	lockdep_assert_held(&ddev->write_lock);
800 
801 	/* Prevent duplicate events. */
802 	if (ddev->state.base.state == info.state &&
803 	    ddev->state.base.base_id == info.base_id)
804 		return;
805 
806 	ddev->state.base = info;
807 
808 	event.e.length = sizeof(struct sdtx_base_info);
809 	event.e.code = SDTX_EVENT_BASE_CONNECTION;
810 	event.v.state = sdtx_translate_base_state(ddev, info.state);
811 	event.v.base_id = SDTX_BASE_TYPE_SSH(info.base_id);
812 
813 	sdtx_push_event(ddev, &event.e);
814 }
815 
816 /* Must be executed with ddev->write_lock held. */
817 static void __sdtx_device_state_update_mode(struct sdtx_device *ddev, u8 mode)
818 {
819 	struct sdtx_status_event event;
820 	int tablet;
821 
822 	/*
823 	 * Note: This function must be called after updating the base state
824 	 * via __sdtx_device_state_update_base(), as we rely on the updated
825 	 * base state value in the validity check below.
826 	 */
827 
828 	lockdep_assert_held(&ddev->write_lock);
829 
830 	if (sdtx_device_mode_invalid(mode, ddev->state.base.state)) {
831 		dev_dbg(ddev->dev, "device mode is invalid, trying again\n");
832 		sdtx_update_device_mode(ddev, SDTX_DEVICE_MODE_DELAY_RECHECK);
833 		return;
834 	}
835 
836 	/* Prevent duplicate events. */
837 	if (ddev->state.device_mode == mode)
838 		return;
839 
840 	ddev->state.device_mode = mode;
841 
842 	/* Send event. */
843 	event.e.length = sizeof(u16);
844 	event.e.code = SDTX_EVENT_DEVICE_MODE;
845 	event.v = mode;
846 
847 	sdtx_push_event(ddev, &event.e);
848 
849 	/* Send SW_TABLET_MODE event. */
850 	tablet = mode != SDTX_DEVICE_MODE_LAPTOP;
851 	input_report_switch(ddev->mode_switch, SW_TABLET_MODE, tablet);
852 	input_sync(ddev->mode_switch);
853 }
854 
855 /* Must be executed with ddev->write_lock held. */
856 static void __sdtx_device_state_update_latch(struct sdtx_device *ddev, u8 status)
857 {
858 	struct sdtx_status_event event;
859 
860 	lockdep_assert_held(&ddev->write_lock);
861 
862 	/* Prevent duplicate events. */
863 	if (ddev->state.latch_status == status)
864 		return;
865 
866 	ddev->state.latch_status = status;
867 
868 	event.e.length = sizeof(struct sdtx_base_info);
869 	event.e.code = SDTX_EVENT_BASE_CONNECTION;
870 	event.v = sdtx_translate_latch_status(ddev, status);
871 
872 	sdtx_push_event(ddev, &event.e);
873 }
874 
875 static void sdtx_device_state_workfn(struct work_struct *work)
876 {
877 	struct sdtx_device *ddev = container_of(work, struct sdtx_device, state_work.work);
878 	struct ssam_bas_base_info base;
879 	u8 mode, latch;
880 	int status;
881 
882 	/* Mark everything as dirty. */
883 	set_bit(SDTX_DEVICE_DIRTY_BASE_BIT, &ddev->flags);
884 	set_bit(SDTX_DEVICE_DIRTY_MODE_BIT, &ddev->flags);
885 	set_bit(SDTX_DEVICE_DIRTY_LATCH_BIT, &ddev->flags);
886 
887 	/*
888 	 * Ensure that the state gets marked as dirty before continuing to
889 	 * query it. Necessary to ensure that clear_bit() calls in
890 	 * sdtx_notifier() and sdtx_device_mode_workfn() actually clear these
891 	 * bits if an event is received while updating the state here.
892 	 */
893 	smp_mb__after_atomic();
894 
895 	status = ssam_retry(ssam_bas_get_base, ddev->ctrl, &base);
896 	if (status) {
897 		dev_err(ddev->dev, "failed to get base state: %d\n", status);
898 		return;
899 	}
900 
901 	status = ssam_retry(ssam_bas_get_device_mode, ddev->ctrl, &mode);
902 	if (status) {
903 		dev_err(ddev->dev, "failed to get device mode: %d\n", status);
904 		return;
905 	}
906 
907 	status = ssam_retry(ssam_bas_get_latch_status, ddev->ctrl, &latch);
908 	if (status) {
909 		dev_err(ddev->dev, "failed to get latch status: %d\n", status);
910 		return;
911 	}
912 
913 	mutex_lock(&ddev->write_lock);
914 
915 	/*
916 	 * If the respective dirty-bit has been cleared, an event has been
917 	 * received, updating this state. The queried state may thus be out of
918 	 * date. At this point, we can safely assume that the state provided
919 	 * by the event is either up to date, or we're about to receive
920 	 * another event updating it.
921 	 */
922 
923 	if (test_and_clear_bit(SDTX_DEVICE_DIRTY_BASE_BIT, &ddev->flags))
924 		__sdtx_device_state_update_base(ddev, base);
925 
926 	if (test_and_clear_bit(SDTX_DEVICE_DIRTY_MODE_BIT, &ddev->flags))
927 		__sdtx_device_state_update_mode(ddev, mode);
928 
929 	if (test_and_clear_bit(SDTX_DEVICE_DIRTY_LATCH_BIT, &ddev->flags))
930 		__sdtx_device_state_update_latch(ddev, latch);
931 
932 	mutex_unlock(&ddev->write_lock);
933 }
934 
935 static void sdtx_update_device_state(struct sdtx_device *ddev, unsigned long delay)
936 {
937 	schedule_delayed_work(&ddev->state_work, delay);
938 }
939 
940 
941 /* -- Common device initialization. ----------------------------------------- */
942 
943 static int sdtx_device_init(struct sdtx_device *ddev, struct device *dev,
944 			    struct ssam_controller *ctrl)
945 {
946 	int status, tablet_mode;
947 
948 	/* Basic initialization. */
949 	kref_init(&ddev->kref);
950 	init_rwsem(&ddev->lock);
951 	ddev->dev = dev;
952 	ddev->ctrl = ctrl;
953 
954 	ddev->mdev.minor = MISC_DYNAMIC_MINOR;
955 	ddev->mdev.name = "surface_dtx";
956 	ddev->mdev.nodename = "surface/dtx";
957 	ddev->mdev.fops = &surface_dtx_fops;
958 
959 	ddev->notif.base.priority = 1;
960 	ddev->notif.base.fn = sdtx_notifier;
961 	ddev->notif.event.reg = SSAM_EVENT_REGISTRY_SAM;
962 	ddev->notif.event.id.target_category = SSAM_SSH_TC_BAS;
963 	ddev->notif.event.id.instance = 0;
964 	ddev->notif.event.mask = SSAM_EVENT_MASK_NONE;
965 	ddev->notif.event.flags = SSAM_EVENT_SEQUENCED;
966 
967 	init_waitqueue_head(&ddev->waitq);
968 	mutex_init(&ddev->write_lock);
969 	init_rwsem(&ddev->client_lock);
970 	INIT_LIST_HEAD(&ddev->client_list);
971 
972 	INIT_DELAYED_WORK(&ddev->mode_work, sdtx_device_mode_workfn);
973 	INIT_DELAYED_WORK(&ddev->state_work, sdtx_device_state_workfn);
974 
975 	/*
976 	 * Get current device state. We want to guarantee that events are only
977 	 * sent when state actually changes. Thus we cannot use special
978 	 * "uninitialized" values, as that would cause problems when manually
979 	 * querying the state in surface_dtx_pm_complete(). I.e. we would not
980 	 * be able to detect state changes there if no change event has been
981 	 * received between driver initialization and first device suspension.
982 	 *
983 	 * Note that we also need to do this before registering the event
984 	 * notifier, as that may access the state values.
985 	 */
986 	status = ssam_retry(ssam_bas_get_base, ddev->ctrl, &ddev->state.base);
987 	if (status)
988 		return status;
989 
990 	status = ssam_retry(ssam_bas_get_device_mode, ddev->ctrl, &ddev->state.device_mode);
991 	if (status)
992 		return status;
993 
994 	status = ssam_retry(ssam_bas_get_latch_status, ddev->ctrl, &ddev->state.latch_status);
995 	if (status)
996 		return status;
997 
998 	/* Set up tablet mode switch. */
999 	ddev->mode_switch = input_allocate_device();
1000 	if (!ddev->mode_switch)
1001 		return -ENOMEM;
1002 
1003 	ddev->mode_switch->name = "Microsoft Surface DTX Device Mode Switch";
1004 	ddev->mode_switch->phys = "ssam/01:11:01:00:00/input0";
1005 	ddev->mode_switch->id.bustype = BUS_HOST;
1006 	ddev->mode_switch->dev.parent = ddev->dev;
1007 
1008 	tablet_mode = (ddev->state.device_mode != SDTX_DEVICE_MODE_LAPTOP);
1009 	input_set_capability(ddev->mode_switch, EV_SW, SW_TABLET_MODE);
1010 	input_report_switch(ddev->mode_switch, SW_TABLET_MODE, tablet_mode);
1011 
1012 	status = input_register_device(ddev->mode_switch);
1013 	if (status) {
1014 		input_free_device(ddev->mode_switch);
1015 		return status;
1016 	}
1017 
1018 	/* Set up event notifier. */
1019 	status = ssam_notifier_register(ddev->ctrl, &ddev->notif);
1020 	if (status)
1021 		goto err_notif;
1022 
1023 	/* Register miscdevice. */
1024 	status = misc_register(&ddev->mdev);
1025 	if (status)
1026 		goto err_mdev;
1027 
1028 	/*
1029 	 * Update device state in case it has changed between getting the
1030 	 * initial mode and registering the event notifier.
1031 	 */
1032 	sdtx_update_device_state(ddev, 0);
1033 	return 0;
1034 
1035 err_notif:
1036 	ssam_notifier_unregister(ddev->ctrl, &ddev->notif);
1037 	cancel_delayed_work_sync(&ddev->mode_work);
1038 err_mdev:
1039 	input_unregister_device(ddev->mode_switch);
1040 	return status;
1041 }
1042 
1043 static struct sdtx_device *sdtx_device_create(struct device *dev, struct ssam_controller *ctrl)
1044 {
1045 	struct sdtx_device *ddev;
1046 	int status;
1047 
1048 	ddev = kzalloc(sizeof(*ddev), GFP_KERNEL);
1049 	if (!ddev)
1050 		return ERR_PTR(-ENOMEM);
1051 
1052 	status = sdtx_device_init(ddev, dev, ctrl);
1053 	if (status) {
1054 		sdtx_device_put(ddev);
1055 		return ERR_PTR(status);
1056 	}
1057 
1058 	return ddev;
1059 }
1060 
1061 static void sdtx_device_destroy(struct sdtx_device *ddev)
1062 {
1063 	struct sdtx_client *client;
1064 
1065 	/*
1066 	 * Mark device as shut-down. Prevent new clients from being added and
1067 	 * new operations from being executed.
1068 	 */
1069 	set_bit(SDTX_DEVICE_SHUTDOWN_BIT, &ddev->flags);
1070 
1071 	/* Disable notifiers, prevent new events from arriving. */
1072 	ssam_notifier_unregister(ddev->ctrl, &ddev->notif);
1073 
1074 	/* Stop mode_work, prevent access to mode_switch. */
1075 	cancel_delayed_work_sync(&ddev->mode_work);
1076 
1077 	/* Stop state_work. */
1078 	cancel_delayed_work_sync(&ddev->state_work);
1079 
1080 	/* With mode_work canceled, we can unregister the mode_switch. */
1081 	input_unregister_device(ddev->mode_switch);
1082 
1083 	/* Wake up async clients. */
1084 	down_write(&ddev->client_lock);
1085 	list_for_each_entry(client, &ddev->client_list, node) {
1086 		kill_fasync(&client->fasync, SIGIO, POLL_HUP);
1087 	}
1088 	up_write(&ddev->client_lock);
1089 
1090 	/* Wake up blocking clients. */
1091 	wake_up_interruptible(&ddev->waitq);
1092 
1093 	/*
1094 	 * Wait for clients to finish their current operation. After this, the
1095 	 * controller and device references are guaranteed to be no longer in
1096 	 * use.
1097 	 */
1098 	down_write(&ddev->lock);
1099 	ddev->dev = NULL;
1100 	ddev->ctrl = NULL;
1101 	up_write(&ddev->lock);
1102 
1103 	/* Finally remove the misc-device. */
1104 	misc_deregister(&ddev->mdev);
1105 
1106 	/*
1107 	 * We're now guaranteed that sdtx_device_open() won't be called any
1108 	 * more, so we can now drop out reference.
1109 	 */
1110 	sdtx_device_put(ddev);
1111 }
1112 
1113 
1114 /* -- PM ops. --------------------------------------------------------------- */
1115 
1116 #ifdef CONFIG_PM_SLEEP
1117 
1118 static void surface_dtx_pm_complete(struct device *dev)
1119 {
1120 	struct sdtx_device *ddev = dev_get_drvdata(dev);
1121 
1122 	/*
1123 	 * Normally, the EC will store events while suspended (i.e. in
1124 	 * display-off state) and release them when resumed (i.e. transitioned
1125 	 * to display-on state). During hibernation, however, the EC will be
1126 	 * shut down and does not store events. Furthermore, events might be
1127 	 * dropped during prolonged suspension (it is currently unknown how
1128 	 * big this event buffer is and how it behaves on overruns).
1129 	 *
1130 	 * To prevent any problems, we update the device state here. We do
1131 	 * this delayed to ensure that any events sent by the EC directly
1132 	 * after resuming will be handled first. The delay below has been
1133 	 * chosen (experimentally), so that there should be ample time for
1134 	 * these events to be handled, before we check and, if necessary,
1135 	 * update the state.
1136 	 */
1137 	sdtx_update_device_state(ddev, msecs_to_jiffies(1000));
1138 }
1139 
1140 static const struct dev_pm_ops surface_dtx_pm_ops = {
1141 	.complete = surface_dtx_pm_complete,
1142 };
1143 
1144 #else /* CONFIG_PM_SLEEP */
1145 
1146 static const struct dev_pm_ops surface_dtx_pm_ops = {};
1147 
1148 #endif /* CONFIG_PM_SLEEP */
1149 
1150 
1151 /* -- Platform driver. ------------------------------------------------------ */
1152 
1153 static int surface_dtx_platform_probe(struct platform_device *pdev)
1154 {
1155 	struct ssam_controller *ctrl;
1156 	struct sdtx_device *ddev;
1157 
1158 	/* Link to EC. */
1159 	ctrl = ssam_client_bind(&pdev->dev);
1160 	if (IS_ERR(ctrl))
1161 		return PTR_ERR(ctrl) == -ENODEV ? -EPROBE_DEFER : PTR_ERR(ctrl);
1162 
1163 	ddev = sdtx_device_create(&pdev->dev, ctrl);
1164 	if (IS_ERR(ddev))
1165 		return PTR_ERR(ddev);
1166 
1167 	platform_set_drvdata(pdev, ddev);
1168 	return 0;
1169 }
1170 
1171 static int surface_dtx_platform_remove(struct platform_device *pdev)
1172 {
1173 	sdtx_device_destroy(platform_get_drvdata(pdev));
1174 	return 0;
1175 }
1176 
1177 static const struct acpi_device_id surface_dtx_acpi_match[] = {
1178 	{ "MSHW0133", 0 },
1179 	{ },
1180 };
1181 MODULE_DEVICE_TABLE(acpi, surface_dtx_acpi_match);
1182 
1183 static struct platform_driver surface_dtx_platform_driver = {
1184 	.probe = surface_dtx_platform_probe,
1185 	.remove = surface_dtx_platform_remove,
1186 	.driver = {
1187 		.name = "surface_dtx_pltf",
1188 		.acpi_match_table = surface_dtx_acpi_match,
1189 		.pm = &surface_dtx_pm_ops,
1190 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
1191 	},
1192 };
1193 
1194 
1195 /* -- SSAM device driver. --------------------------------------------------- */
1196 
1197 #ifdef CONFIG_SURFACE_AGGREGATOR_BUS
1198 
1199 static int surface_dtx_ssam_probe(struct ssam_device *sdev)
1200 {
1201 	struct sdtx_device *ddev;
1202 
1203 	ddev = sdtx_device_create(&sdev->dev, sdev->ctrl);
1204 	if (IS_ERR(ddev))
1205 		return PTR_ERR(ddev);
1206 
1207 	ssam_device_set_drvdata(sdev, ddev);
1208 	return 0;
1209 }
1210 
1211 static void surface_dtx_ssam_remove(struct ssam_device *sdev)
1212 {
1213 	sdtx_device_destroy(ssam_device_get_drvdata(sdev));
1214 }
1215 
1216 static const struct ssam_device_id surface_dtx_ssam_match[] = {
1217 	{ SSAM_SDEV(BAS, 0x01, 0x00, 0x00) },
1218 	{ },
1219 };
1220 MODULE_DEVICE_TABLE(ssam, surface_dtx_ssam_match);
1221 
1222 static struct ssam_device_driver surface_dtx_ssam_driver = {
1223 	.probe = surface_dtx_ssam_probe,
1224 	.remove = surface_dtx_ssam_remove,
1225 	.match_table = surface_dtx_ssam_match,
1226 	.driver = {
1227 		.name = "surface_dtx",
1228 		.pm = &surface_dtx_pm_ops,
1229 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
1230 	},
1231 };
1232 
1233 static int ssam_dtx_driver_register(void)
1234 {
1235 	return ssam_device_driver_register(&surface_dtx_ssam_driver);
1236 }
1237 
1238 static void ssam_dtx_driver_unregister(void)
1239 {
1240 	ssam_device_driver_unregister(&surface_dtx_ssam_driver);
1241 }
1242 
1243 #else /* CONFIG_SURFACE_AGGREGATOR_BUS */
1244 
1245 static int ssam_dtx_driver_register(void)
1246 {
1247 	return 0;
1248 }
1249 
1250 static void ssam_dtx_driver_unregister(void)
1251 {
1252 }
1253 
1254 #endif /* CONFIG_SURFACE_AGGREGATOR_BUS */
1255 
1256 
1257 /* -- Module setup. --------------------------------------------------------- */
1258 
1259 static int __init surface_dtx_init(void)
1260 {
1261 	int status;
1262 
1263 	status = ssam_dtx_driver_register();
1264 	if (status)
1265 		return status;
1266 
1267 	status = platform_driver_register(&surface_dtx_platform_driver);
1268 	if (status)
1269 		ssam_dtx_driver_unregister();
1270 
1271 	return status;
1272 }
1273 module_init(surface_dtx_init);
1274 
1275 static void __exit surface_dtx_exit(void)
1276 {
1277 	platform_driver_unregister(&surface_dtx_platform_driver);
1278 	ssam_dtx_driver_unregister();
1279 }
1280 module_exit(surface_dtx_exit);
1281 
1282 MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
1283 MODULE_DESCRIPTION("Detachment-system driver for Surface System Aggregator Module");
1284 MODULE_LICENSE("GPL");
1285