1 /*
2  * Copyright (C) 2011 Google, Inc.
3  * Copyright (C) 2012 Intel, Inc.
4  * Copyright (C) 2013 Intel, Inc.
5  * Copyright (C) 2014 Linaro Limited
6  *
7  * This software is licensed under the terms of the GNU General Public
8  * License version 2, as published by the Free Software Foundation, and
9  * may be copied, distributed, and modified under those terms.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  * GNU General Public License for more details.
15  *
16  */
17 
18 /* This source file contains the implementation of a special device driver
19  * that intends to provide a *very* fast communication channel between the
20  * guest system and the QEMU emulator.
21  *
22  * Usage from the guest is simply the following (error handling simplified):
23  *
24  *    int  fd = open("/dev/qemu_pipe",O_RDWR);
25  *    .... write() or read() through the pipe.
26  *
27  * This driver doesn't deal with the exact protocol used during the session.
28  * It is intended to be as simple as something like:
29  *
30  *    // do this _just_ after opening the fd to connect to a specific
31  *    // emulator service.
32  *    const char*  msg = "<pipename>";
33  *    if (write(fd, msg, strlen(msg)+1) < 0) {
34  *       ... could not connect to <pipename> service
35  *       close(fd);
36  *    }
37  *
38  *    // after this, simply read() and write() to communicate with the
39  *    // service. Exact protocol details left as an exercise to the reader.
40  *
41  * This driver is very fast because it doesn't copy any data through
42  * intermediate buffers, since the emulator is capable of translating
43  * guest user addresses into host ones.
44  *
45  * Note that we must however ensure that each user page involved in the
46  * exchange is properly mapped during a transfer.
47  */
48 
49 #include <linux/module.h>
50 #include <linux/interrupt.h>
51 #include <linux/kernel.h>
52 #include <linux/spinlock.h>
53 #include <linux/miscdevice.h>
54 #include <linux/platform_device.h>
55 #include <linux/poll.h>
56 #include <linux/sched.h>
57 #include <linux/bitops.h>
58 #include <linux/slab.h>
59 #include <linux/io.h>
60 #include <linux/goldfish.h>
61 #include <linux/dma-mapping.h>
62 #include <linux/mm.h>
63 #include <linux/acpi.h>
64 
65 /*
66  * IMPORTANT: The following constants must match the ones used and defined
67  * in external/qemu/hw/goldfish_pipe.c in the Android source tree.
68  */
69 
70 /* pipe device registers */
71 #define PIPE_REG_COMMAND		0x00  /* write: value = command */
72 #define PIPE_REG_STATUS			0x04  /* read */
73 #define PIPE_REG_CHANNEL		0x08  /* read/write: channel id */
74 #define PIPE_REG_CHANNEL_HIGH	        0x30  /* read/write: channel id */
75 #define PIPE_REG_SIZE			0x0c  /* read/write: buffer size */
76 #define PIPE_REG_ADDRESS		0x10  /* write: physical address */
77 #define PIPE_REG_ADDRESS_HIGH	        0x34  /* write: physical address */
78 #define PIPE_REG_WAKES			0x14  /* read: wake flags */
79 #define PIPE_REG_PARAMS_ADDR_LOW	0x18  /* read/write: batch data address */
80 #define PIPE_REG_PARAMS_ADDR_HIGH	0x1c  /* read/write: batch data address */
81 #define PIPE_REG_ACCESS_PARAMS		0x20  /* write: batch access */
82 #define PIPE_REG_VERSION		0x24  /* read: device version */
83 
84 /* list of commands for PIPE_REG_COMMAND */
85 #define CMD_OPEN			1  /* open new channel */
86 #define CMD_CLOSE			2  /* close channel (from guest) */
87 #define CMD_POLL			3  /* poll read/write status */
88 
89 /* List of bitflags returned in status of CMD_POLL command */
90 #define PIPE_POLL_IN			(1 << 0)
91 #define PIPE_POLL_OUT			(1 << 1)
92 #define PIPE_POLL_HUP			(1 << 2)
93 
94 /* The following commands are related to write operations */
95 #define CMD_WRITE_BUFFER	4  /* send a user buffer to the emulator */
96 #define CMD_WAKE_ON_WRITE	5  /* tell the emulator to wake us when writing
97 				     is possible */
98 #define CMD_READ_BUFFER        6  /* receive a user buffer from the emulator */
99 #define CMD_WAKE_ON_READ       7  /* tell the emulator to wake us when reading
100 				   * is possible */
101 
102 /* Possible status values used to signal errors - see goldfish_pipe_error_convert */
103 #define PIPE_ERROR_INVAL       -1
104 #define PIPE_ERROR_AGAIN       -2
105 #define PIPE_ERROR_NOMEM       -3
106 #define PIPE_ERROR_IO          -4
107 
108 /* Bit-flags used to signal events from the emulator */
109 #define PIPE_WAKE_CLOSED       (1 << 0)  /* emulator closed pipe */
110 #define PIPE_WAKE_READ         (1 << 1)  /* pipe can now be read from */
111 #define PIPE_WAKE_WRITE        (1 << 2)  /* pipe can now be written to */
112 
113 struct access_params {
114 	unsigned long channel;
115 	u32 size;
116 	unsigned long address;
117 	u32 cmd;
118 	u32 result;
119 	/* reserved for future extension */
120 	u32 flags;
121 };
122 
123 /* The global driver data. Holds a reference to the i/o page used to
124  * communicate with the emulator, and a wake queue for blocked tasks
125  * waiting to be awoken.
126  */
127 struct goldfish_pipe_dev {
128 	spinlock_t lock;
129 	unsigned char __iomem *base;
130 	struct access_params *aps;
131 	int irq;
132 	u32 version;
133 };
134 
135 static struct goldfish_pipe_dev   pipe_dev[1];
136 
137 /* This data type models a given pipe instance */
138 struct goldfish_pipe {
139 	struct goldfish_pipe_dev *dev;
140 	struct mutex lock;
141 	unsigned long flags;
142 	wait_queue_head_t wake_queue;
143 };
144 
145 
146 /* Bit flags for the 'flags' field */
147 enum {
148 	BIT_CLOSED_ON_HOST = 0,  /* pipe closed by host */
149 	BIT_WAKE_ON_WRITE  = 1,  /* want to be woken on writes */
150 	BIT_WAKE_ON_READ   = 2,  /* want to be woken on reads */
151 };
152 
153 
154 static u32 goldfish_cmd_status(struct goldfish_pipe *pipe, u32 cmd)
155 {
156 	unsigned long flags;
157 	u32 status;
158 	struct goldfish_pipe_dev *dev = pipe->dev;
159 
160 	spin_lock_irqsave(&dev->lock, flags);
161 	gf_write_ptr(pipe, dev->base + PIPE_REG_CHANNEL,
162 		     dev->base + PIPE_REG_CHANNEL_HIGH);
163 	writel(cmd, dev->base + PIPE_REG_COMMAND);
164 	status = readl(dev->base + PIPE_REG_STATUS);
165 	spin_unlock_irqrestore(&dev->lock, flags);
166 	return status;
167 }
168 
169 static void goldfish_cmd(struct goldfish_pipe *pipe, u32 cmd)
170 {
171 	unsigned long flags;
172 	struct goldfish_pipe_dev *dev = pipe->dev;
173 
174 	spin_lock_irqsave(&dev->lock, flags);
175 	gf_write_ptr(pipe, dev->base + PIPE_REG_CHANNEL,
176 		     dev->base + PIPE_REG_CHANNEL_HIGH);
177 	writel(cmd, dev->base + PIPE_REG_COMMAND);
178 	spin_unlock_irqrestore(&dev->lock, flags);
179 }
180 
181 /* This function converts an error code returned by the emulator through
182  * the PIPE_REG_STATUS i/o register into a valid negative errno value.
183  */
184 static int goldfish_pipe_error_convert(int status)
185 {
186 	switch (status) {
187 	case PIPE_ERROR_AGAIN:
188 		return -EAGAIN;
189 	case PIPE_ERROR_NOMEM:
190 		return -ENOMEM;
191 	case PIPE_ERROR_IO:
192 		return -EIO;
193 	default:
194 		return -EINVAL;
195 	}
196 }
197 
198 /*
199  * Notice: QEMU will return 0 for un-known register access, indicating
200  * param_acess is supported or not
201  */
202 static int valid_batchbuffer_addr(struct goldfish_pipe_dev *dev,
203 				  struct access_params *aps)
204 {
205 	u32 aph, apl;
206 	u64 paddr;
207 	aph = readl(dev->base + PIPE_REG_PARAMS_ADDR_HIGH);
208 	apl = readl(dev->base + PIPE_REG_PARAMS_ADDR_LOW);
209 
210 	paddr = ((u64)aph << 32) | apl;
211 	if (paddr != (__pa(aps)))
212 		return 0;
213 	return 1;
214 }
215 
216 /* 0 on success */
217 static int setup_access_params_addr(struct platform_device *pdev,
218 					struct goldfish_pipe_dev *dev)
219 {
220 	dma_addr_t dma_handle;
221 	struct access_params *aps;
222 
223 	aps = dmam_alloc_coherent(&pdev->dev, sizeof(struct access_params),
224 				  &dma_handle, GFP_KERNEL);
225 	if (!aps)
226 		return -ENOMEM;
227 
228 	writel(upper_32_bits(dma_handle), dev->base + PIPE_REG_PARAMS_ADDR_HIGH);
229 	writel(lower_32_bits(dma_handle), dev->base + PIPE_REG_PARAMS_ADDR_LOW);
230 
231 	if (valid_batchbuffer_addr(dev, aps)) {
232 		dev->aps = aps;
233 		return 0;
234 	} else
235 		return -1;
236 }
237 
238 /* A value that will not be set by qemu emulator */
239 #define INITIAL_BATCH_RESULT (0xdeadbeaf)
240 static int access_with_param(struct goldfish_pipe_dev *dev, const int cmd,
241 				unsigned long address, unsigned long avail,
242 				struct goldfish_pipe *pipe, int *status)
243 {
244 	struct access_params *aps = dev->aps;
245 
246 	if (aps == NULL)
247 		return -1;
248 
249 	aps->result = INITIAL_BATCH_RESULT;
250 	aps->channel = (unsigned long)pipe;
251 	aps->size = avail;
252 	aps->address = address;
253 	aps->cmd = cmd;
254 	writel(cmd, dev->base + PIPE_REG_ACCESS_PARAMS);
255 	/*
256 	 * If the aps->result has not changed, that means
257 	 * that the batch command failed
258 	 */
259 	if (aps->result == INITIAL_BATCH_RESULT)
260 		return -1;
261 	*status = aps->result;
262 	return 0;
263 }
264 
265 static ssize_t goldfish_pipe_read_write(struct file *filp, char __user *buffer,
266 				       size_t bufflen, int is_write)
267 {
268 	unsigned long irq_flags;
269 	struct goldfish_pipe *pipe = filp->private_data;
270 	struct goldfish_pipe_dev *dev = pipe->dev;
271 	unsigned long address, address_end;
272 	int count = 0, ret = -EINVAL;
273 
274 	/* If the emulator already closed the pipe, no need to go further */
275 	if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
276 		return -EIO;
277 
278 	/* Null reads or writes succeeds */
279 	if (unlikely(bufflen == 0))
280 		return 0;
281 
282 	/* Check the buffer range for access */
283 	if (!access_ok(is_write ? VERIFY_WRITE : VERIFY_READ,
284 			buffer, bufflen))
285 		return -EFAULT;
286 
287 	/* Serialize access to the pipe */
288 	if (mutex_lock_interruptible(&pipe->lock))
289 		return -ERESTARTSYS;
290 
291 	address = (unsigned long)(void *)buffer;
292 	address_end = address + bufflen;
293 
294 	while (address < address_end) {
295 		unsigned long page_end = (address & PAGE_MASK) + PAGE_SIZE;
296 		unsigned long next     = page_end < address_end ? page_end
297 								: address_end;
298 		unsigned long avail    = next - address;
299 		int status, wakeBit;
300 		struct page *page;
301 
302 		/* Either vaddr or paddr depending on the device version */
303 		unsigned long xaddr;
304 
305 		/*
306 		 * We grab the pages on a page-by-page basis in case user
307 		 * space gives us a potentially huge buffer but the read only
308 		 * returns a small amount, then there's no need to pin that
309 		 * much memory to the process.
310 		 */
311 		ret = get_user_pages_unlocked(address, 1, &page,
312 				is_write ? 0 : FOLL_WRITE);
313 		if (ret < 0)
314 			break;
315 
316 		if (dev->version) {
317 			/* Device version 1 or newer (qemu-android) expects the
318 			 * physical address.
319 			 */
320 			xaddr = page_to_phys(page) | (address & ~PAGE_MASK);
321 		} else {
322 			/* Device version 0 (classic emulator) expects the
323 			 * virtual address.
324 			 */
325 			xaddr = address;
326 		}
327 
328 		/* Now, try to transfer the bytes in the current page */
329 		spin_lock_irqsave(&dev->lock, irq_flags);
330 		if (access_with_param(dev,
331 				is_write ? CMD_WRITE_BUFFER : CMD_READ_BUFFER,
332 				xaddr, avail, pipe, &status)) {
333 			gf_write_ptr(pipe, dev->base + PIPE_REG_CHANNEL,
334 				     dev->base + PIPE_REG_CHANNEL_HIGH);
335 			writel(avail, dev->base + PIPE_REG_SIZE);
336 			gf_write_ptr((void *)xaddr,
337 				     dev->base + PIPE_REG_ADDRESS,
338 				     dev->base + PIPE_REG_ADDRESS_HIGH);
339 			writel(is_write ? CMD_WRITE_BUFFER : CMD_READ_BUFFER,
340 					dev->base + PIPE_REG_COMMAND);
341 			status = readl(dev->base + PIPE_REG_STATUS);
342 		}
343 		spin_unlock_irqrestore(&dev->lock, irq_flags);
344 
345 		if (status > 0 && !is_write)
346 			set_page_dirty(page);
347 		put_page(page);
348 
349 		if (status > 0) { /* Correct transfer */
350 			count += status;
351 			address += status;
352 			continue;
353 		} else if (status == 0) { /* EOF */
354 			ret = 0;
355 			break;
356 		} else if (status < 0 && count > 0) {
357 			/*
358 			 * An error occurred and we already transferred
359 			 * something on one of the previous pages.
360 			 * Just return what we already copied and log this
361 			 * err.
362 			 *
363 			 * Note: This seems like an incorrect approach but
364 			 * cannot change it until we check if any user space
365 			 * ABI relies on this behavior.
366 			 */
367 			if (status != PIPE_ERROR_AGAIN)
368 				pr_info_ratelimited("goldfish_pipe: backend returned error %d on %s\n",
369 					status, is_write ? "write" : "read");
370 			ret = 0;
371 			break;
372 		}
373 
374 		/*
375 		 * If the error is not PIPE_ERROR_AGAIN, or if we are not in
376 		 * non-blocking mode, just return the error code.
377 		 */
378 		if (status != PIPE_ERROR_AGAIN ||
379 			(filp->f_flags & O_NONBLOCK) != 0) {
380 			ret = goldfish_pipe_error_convert(status);
381 			break;
382 		}
383 
384 		/*
385 		 * The backend blocked the read/write, wait until the backend
386 		 * tells us it's ready to process more data.
387 		 */
388 		wakeBit = is_write ? BIT_WAKE_ON_WRITE : BIT_WAKE_ON_READ;
389 		set_bit(wakeBit, &pipe->flags);
390 
391 		/* Tell the emulator we're going to wait for a wake event */
392 		goldfish_cmd(pipe,
393 			is_write ? CMD_WAKE_ON_WRITE : CMD_WAKE_ON_READ);
394 
395 		/* Unlock the pipe, then wait for the wake signal */
396 		mutex_unlock(&pipe->lock);
397 
398 		while (test_bit(wakeBit, &pipe->flags)) {
399 			if (wait_event_interruptible(
400 					pipe->wake_queue,
401 					!test_bit(wakeBit, &pipe->flags)))
402 				return -ERESTARTSYS;
403 
404 			if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
405 				return -EIO;
406 		}
407 
408 		/* Try to re-acquire the lock */
409 		if (mutex_lock_interruptible(&pipe->lock))
410 			return -ERESTARTSYS;
411 	}
412 	mutex_unlock(&pipe->lock);
413 
414 	if (ret < 0)
415 		return ret;
416 	else
417 		return count;
418 }
419 
420 static ssize_t goldfish_pipe_read(struct file *filp, char __user *buffer,
421 			      size_t bufflen, loff_t *ppos)
422 {
423 	return goldfish_pipe_read_write(filp, buffer, bufflen, 0);
424 }
425 
426 static ssize_t goldfish_pipe_write(struct file *filp,
427 				const char __user *buffer, size_t bufflen,
428 				loff_t *ppos)
429 {
430 	return goldfish_pipe_read_write(filp, (char __user *)buffer,
431 								bufflen, 1);
432 }
433 
434 
435 static unsigned int goldfish_pipe_poll(struct file *filp, poll_table *wait)
436 {
437 	struct goldfish_pipe *pipe = filp->private_data;
438 	unsigned int mask = 0;
439 	int status;
440 
441 	mutex_lock(&pipe->lock);
442 
443 	poll_wait(filp, &pipe->wake_queue, wait);
444 
445 	status = goldfish_cmd_status(pipe, CMD_POLL);
446 
447 	mutex_unlock(&pipe->lock);
448 
449 	if (status & PIPE_POLL_IN)
450 		mask |= POLLIN | POLLRDNORM;
451 
452 	if (status & PIPE_POLL_OUT)
453 		mask |= POLLOUT | POLLWRNORM;
454 
455 	if (status & PIPE_POLL_HUP)
456 		mask |= POLLHUP;
457 
458 	if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
459 		mask |= POLLERR;
460 
461 	return mask;
462 }
463 
464 static irqreturn_t goldfish_pipe_interrupt(int irq, void *dev_id)
465 {
466 	struct goldfish_pipe_dev *dev = dev_id;
467 	unsigned long irq_flags;
468 	int count = 0;
469 
470 	/*
471 	 * We're going to read from the emulator a list of (channel,flags)
472 	 * pairs corresponding to the wake events that occurred on each
473 	 * blocked pipe (i.e. channel).
474 	 */
475 	spin_lock_irqsave(&dev->lock, irq_flags);
476 	for (;;) {
477 		/* First read the channel, 0 means the end of the list */
478 		struct goldfish_pipe *pipe;
479 		unsigned long wakes;
480 		unsigned long channel = 0;
481 
482 #ifdef CONFIG_64BIT
483 		channel = (u64)readl(dev->base + PIPE_REG_CHANNEL_HIGH) << 32;
484 
485 		if (channel == 0)
486 			break;
487 #endif
488 		channel |= readl(dev->base + PIPE_REG_CHANNEL);
489 
490 		if (channel == 0)
491 			break;
492 
493 		/* Convert channel to struct pipe pointer + read wake flags */
494 		wakes = readl(dev->base + PIPE_REG_WAKES);
495 		pipe  = (struct goldfish_pipe *)(ptrdiff_t)channel;
496 
497 		/* Did the emulator just closed a pipe? */
498 		if (wakes & PIPE_WAKE_CLOSED) {
499 			set_bit(BIT_CLOSED_ON_HOST, &pipe->flags);
500 			wakes |= PIPE_WAKE_READ | PIPE_WAKE_WRITE;
501 		}
502 		if (wakes & PIPE_WAKE_READ)
503 			clear_bit(BIT_WAKE_ON_READ, &pipe->flags);
504 		if (wakes & PIPE_WAKE_WRITE)
505 			clear_bit(BIT_WAKE_ON_WRITE, &pipe->flags);
506 
507 		wake_up_interruptible(&pipe->wake_queue);
508 		count++;
509 	}
510 	spin_unlock_irqrestore(&dev->lock, irq_flags);
511 
512 	return (count == 0) ? IRQ_NONE : IRQ_HANDLED;
513 }
514 
515 /**
516  *	goldfish_pipe_open	-	open a channel to the AVD
517  *	@inode: inode of device
518  *	@file: file struct of opener
519  *
520  *	Create a new pipe link between the emulator and the use application.
521  *	Each new request produces a new pipe.
522  *
523  *	Note: we use the pipe ID as a mux. All goldfish emulations are 32bit
524  *	right now so this is fine. A move to 64bit will need this addressing
525  */
526 static int goldfish_pipe_open(struct inode *inode, struct file *file)
527 {
528 	struct goldfish_pipe *pipe;
529 	struct goldfish_pipe_dev *dev = pipe_dev;
530 	int32_t status;
531 
532 	/* Allocate new pipe kernel object */
533 	pipe = kzalloc(sizeof(*pipe), GFP_KERNEL);
534 	if (pipe == NULL)
535 		return -ENOMEM;
536 
537 	pipe->dev = dev;
538 	mutex_init(&pipe->lock);
539 	init_waitqueue_head(&pipe->wake_queue);
540 
541 	/*
542 	 * Now, tell the emulator we're opening a new pipe. We use the
543 	 * pipe object's address as the channel identifier for simplicity.
544 	 */
545 
546 	status = goldfish_cmd_status(pipe, CMD_OPEN);
547 	if (status < 0) {
548 		kfree(pipe);
549 		return status;
550 	}
551 
552 	/* All is done, save the pipe into the file's private data field */
553 	file->private_data = pipe;
554 	return 0;
555 }
556 
557 static int goldfish_pipe_release(struct inode *inode, struct file *filp)
558 {
559 	struct goldfish_pipe *pipe = filp->private_data;
560 
561 	/* The guest is closing the channel, so tell the emulator right now */
562 	goldfish_cmd(pipe, CMD_CLOSE);
563 	kfree(pipe);
564 	filp->private_data = NULL;
565 	return 0;
566 }
567 
568 static const struct file_operations goldfish_pipe_fops = {
569 	.owner = THIS_MODULE,
570 	.read = goldfish_pipe_read,
571 	.write = goldfish_pipe_write,
572 	.poll = goldfish_pipe_poll,
573 	.open = goldfish_pipe_open,
574 	.release = goldfish_pipe_release,
575 };
576 
577 static struct miscdevice goldfish_pipe_device = {
578 	.minor = MISC_DYNAMIC_MINOR,
579 	.name = "goldfish_pipe",
580 	.fops = &goldfish_pipe_fops,
581 };
582 
583 static int goldfish_pipe_probe(struct platform_device *pdev)
584 {
585 	int err;
586 	struct resource *r;
587 	struct goldfish_pipe_dev *dev = pipe_dev;
588 
589 	/* not thread safe, but this should not happen */
590 	WARN_ON(dev->base != NULL);
591 
592 	spin_lock_init(&dev->lock);
593 
594 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
595 	if (r == NULL || resource_size(r) < PAGE_SIZE) {
596 		dev_err(&pdev->dev, "can't allocate i/o page\n");
597 		return -EINVAL;
598 	}
599 	dev->base = devm_ioremap(&pdev->dev, r->start, PAGE_SIZE);
600 	if (dev->base == NULL) {
601 		dev_err(&pdev->dev, "ioremap failed\n");
602 		return -EINVAL;
603 	}
604 
605 	r = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
606 	if (r == NULL) {
607 		err = -EINVAL;
608 		goto error;
609 	}
610 	dev->irq = r->start;
611 
612 	err = devm_request_irq(&pdev->dev, dev->irq, goldfish_pipe_interrupt,
613 				IRQF_SHARED, "goldfish_pipe", dev);
614 	if (err) {
615 		dev_err(&pdev->dev, "unable to allocate IRQ\n");
616 		goto error;
617 	}
618 
619 	err = misc_register(&goldfish_pipe_device);
620 	if (err) {
621 		dev_err(&pdev->dev, "unable to register device\n");
622 		goto error;
623 	}
624 	setup_access_params_addr(pdev, dev);
625 
626 	/* Although the pipe device in the classic Android emulator does not
627 	 * recognize the 'version' register, it won't treat this as an error
628 	 * either and will simply return 0, which is fine.
629 	 */
630 	dev->version = readl(dev->base + PIPE_REG_VERSION);
631 	return 0;
632 
633 error:
634 	dev->base = NULL;
635 	return err;
636 }
637 
638 static int goldfish_pipe_remove(struct platform_device *pdev)
639 {
640 	struct goldfish_pipe_dev *dev = pipe_dev;
641 	misc_deregister(&goldfish_pipe_device);
642 	dev->base = NULL;
643 	return 0;
644 }
645 
646 static const struct acpi_device_id goldfish_pipe_acpi_match[] = {
647 	{ "GFSH0003", 0 },
648 	{ },
649 };
650 MODULE_DEVICE_TABLE(acpi, goldfish_pipe_acpi_match);
651 
652 static const struct of_device_id goldfish_pipe_of_match[] = {
653 	{ .compatible = "google,android-pipe", },
654 	{},
655 };
656 MODULE_DEVICE_TABLE(of, goldfish_pipe_of_match);
657 
658 static struct platform_driver goldfish_pipe = {
659 	.probe = goldfish_pipe_probe,
660 	.remove = goldfish_pipe_remove,
661 	.driver = {
662 		.name = "goldfish_pipe",
663 		.owner = THIS_MODULE,
664 		.of_match_table = goldfish_pipe_of_match,
665 		.acpi_match_table = ACPI_PTR(goldfish_pipe_acpi_match),
666 	}
667 };
668 
669 module_platform_driver(goldfish_pipe);
670 MODULE_AUTHOR("David Turner <digit@google.com>");
671 MODULE_LICENSE("GPL");
672