Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 950 insertions, 0 deletions

diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
new file mode 100644
index 000000000..7737d5619
--- /dev/null
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -0,0 +1,950 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2012 Intel, Inc.
+ * Copyright (C) 2013 Intel, Inc.
+ * Copyright (C) 2014 Linaro Limited
+ * Copyright (C) 2011-2016 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+/* This source file contains the implementation of a special device driver
+ * that intends to provide a *very* fast communication channel between the
+ * guest system and the QEMU emulator.
+ *
+ * Usage from the guest is simply the following (error handling simplified):
+ *
+ *    int  fd = open("/dev/qemu_pipe",O_RDWR);
+ *    .... write() or read() through the pipe.
+ *
+ * This driver doesn't deal with the exact protocol used during the session.
+ * It is intended to be as simple as something like:
+ *
+ *    // do this _just_ after opening the fd to connect to a specific
+ *    // emulator service.
+ *    const char*  msg = "<pipename>";
+ *    if (write(fd, msg, strlen(msg)+1) < 0) {
+ *       ... could not connect to <pipename> service
+ *       close(fd);
+ *    }
+ *
+ *    // after this, simply read() and write() to communicate with the
+ *    // service. Exact protocol details left as an exercise to the reader.
+ *
+ * This driver is very fast because it doesn't copy any data through
+ * intermediate buffers, since the emulator is capable of translating
+ * guest user addresses into host ones.
+ *
+ * Note that we must however ensure that each user page involved in the
+ * exchange is properly mapped during a transfer.
+ */
+
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/miscdevice.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/bitops.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/dma-mapping.h>
+#include <linux/mm.h>
+#include <linux/acpi.h>
+#include <linux/bug.h>
+#include "goldfish_pipe_qemu.h"
+
+/*
+ * Update this when something changes in the driver's behavior so the host
+ * can benefit from knowing it
+ */
+enum {
+	PIPE_DRIVER_VERSION = 2,
+	PIPE_CURRENT_DEVICE_VERSION = 2
+};
+
+enum {
+	MAX_BUFFERS_PER_COMMAND = 336,
+	MAX_SIGNALLED_PIPES = 64,
+	INITIAL_PIPES_CAPACITY = 64
+};
+
+struct goldfish_pipe_dev;
+
+/* A per-pipe command structure, shared with the host */
+struct goldfish_pipe_command {
+	s32 cmd;	/* PipeCmdCode, guest -> host */
+	s32 id;		/* pipe id, guest -> host */
+	s32 status;	/* command execution status, host -> guest */
+	s32 reserved;	/* to pad to 64-bit boundary */
+	union {
+		/* Parameters for PIPE_CMD_{READ,WRITE} */
+		struct {
+			/* number of buffers, guest -> host */
+			u32 buffers_count;
+			/* number of consumed bytes, host -> guest */
+			s32 consumed_size;
+			/* buffer pointers, guest -> host */
+			u64 ptrs[MAX_BUFFERS_PER_COMMAND];
+			/* buffer sizes, guest -> host */
+			u32 sizes[MAX_BUFFERS_PER_COMMAND];
+		} rw_params;
+	};
+};
+
+/* A single signalled pipe information */
+struct signalled_pipe_buffer {
+	u32 id;
+	u32 flags;
+};
+
+/* Parameters for the PIPE_CMD_OPEN command */
+struct open_command_param {
+	u64 command_buffer_ptr;
+	u32 rw_params_max_count;
+};
+
+/* Device-level set of buffers shared with the host */
+struct goldfish_pipe_dev_buffers {
+	struct open_command_param open_command_params;
+	struct signalled_pipe_buffer
+		signalled_pipe_buffers[MAX_SIGNALLED_PIPES];
+};
+
+/* This data type models a given pipe instance */
+struct goldfish_pipe {
+	/* pipe ID - index into goldfish_pipe_dev::pipes array */
+	u32 id;
+
+	/* The wake flags pipe is waiting for
+	 * Note: not protected with any lock, uses atomic operations
+	 *  and barriers to make it thread-safe.
+	 */
+	unsigned long flags;
+
+	/* wake flags host have signalled,
+	 *  - protected by goldfish_pipe_dev::lock
+	 */
+	unsigned long signalled_flags;
+
+	/* A pointer to command buffer */
+	struct goldfish_pipe_command *command_buffer;
+
+	/* doubly linked list of signalled pipes, protected by
+	 * goldfish_pipe_dev::lock
+	 */
+	struct goldfish_pipe *prev_signalled;
+	struct goldfish_pipe *next_signalled;
+
+	/*
+	 * A pipe's own lock. Protects the following:
+	 *  - *command_buffer - makes sure a command can safely write its
+	 *    parameters to the host and read the results back.
+	 */
+	struct mutex lock;
+
+	/* A wake queue for sleeping until host signals an event */
+	wait_queue_head_t wake_queue;
+
+	/* Pointer to the parent goldfish_pipe_dev instance */
+	struct goldfish_pipe_dev *dev;
+
+	/* A buffer of pages, too large to fit into a stack frame */
+	struct page *pages[MAX_BUFFERS_PER_COMMAND];
+};
+
+/* The global driver data. Holds a reference to the i/o page used to
+ * communicate with the emulator, and a wake queue for blocked tasks
+ * waiting to be awoken.
+ */
+struct goldfish_pipe_dev {
+	/* A magic number to check if this is an instance of this struct */
+	void *magic;
+
+	/*
+	 * Global device spinlock. Protects the following members:
+	 *  - pipes, pipes_capacity
+	 *  - [*pipes, *pipes + pipes_capacity) - array data
+	 *  - first_signalled_pipe,
+	 *      goldfish_pipe::prev_signalled,
+	 *      goldfish_pipe::next_signalled,
+	 *      goldfish_pipe::signalled_flags - all singnalled-related fields,
+	 *                                       in all allocated pipes
+	 *  - open_command_params - PIPE_CMD_OPEN-related buffers
+	 *
+	 * It looks like a lot of different fields, but the trick is that
+	 * the only operation that happens often is the signalled pipes array
+	 * manipulation. That's why it's OK for now to keep the rest of the
+	 * fields under the same lock. If we notice too much contention because
+	 * of PIPE_CMD_OPEN, then we should add a separate lock there.
+	 */
+	spinlock_t lock;
+
+	/*
+	 * Array of the pipes of |pipes_capacity| elements,
+	 * indexed by goldfish_pipe::id
+	 */
+	struct goldfish_pipe **pipes;
+	u32 pipes_capacity;
+
+	/* Pointers to the buffers host uses for interaction with this driver */
+	struct goldfish_pipe_dev_buffers *buffers;
+
+	/* Head of a doubly linked list of signalled pipes */
+	struct goldfish_pipe *first_signalled_pipe;
+
+	/* ptr to platform device's device struct */
+	struct device *pdev_dev;
+
+	/* Some device-specific data */
+	int irq;
+	int version;
+	unsigned char __iomem *base;
+
+	struct miscdevice miscdev;
+};
+
+static int goldfish_pipe_cmd_locked(struct goldfish_pipe *pipe,
+				    enum PipeCmdCode cmd)
+{
+	pipe->command_buffer->cmd = cmd;
+	/* failure by default */
+	pipe->command_buffer->status = PIPE_ERROR_INVAL;
+	writel(pipe->id, pipe->dev->base + PIPE_REG_CMD);
+	return pipe->command_buffer->status;
+}
+
+static int goldfish_pipe_cmd(struct goldfish_pipe *pipe, enum PipeCmdCode cmd)
+{
+	int status;
+
+	if (mutex_lock_interruptible(&pipe->lock))
+		return PIPE_ERROR_IO;
+	status = goldfish_pipe_cmd_locked(pipe, cmd);
+	mutex_unlock(&pipe->lock);
+	return status;
+}
+
+/*
+ * This function converts an error code returned by the emulator through
+ * the PIPE_REG_STATUS i/o register into a valid negative errno value.
+ */
+static int goldfish_pipe_error_convert(int status)
+{
+	switch (status) {
+	case PIPE_ERROR_AGAIN:
+		return -EAGAIN;
+	case PIPE_ERROR_NOMEM:
+		return -ENOMEM;
+	case PIPE_ERROR_IO:
+		return -EIO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int goldfish_pin_pages(unsigned long first_page,
+			      unsigned long last_page,
+			      unsigned int last_page_size,
+			      int is_write,
+			      struct page *pages[MAX_BUFFERS_PER_COMMAND],
+			      unsigned int *iter_last_page_size)
+{
+	int ret;
+	int requested_pages = ((last_page - first_page) >> PAGE_SHIFT) + 1;
+
+	if (requested_pages > MAX_BUFFERS_PER_COMMAND) {
+		requested_pages = MAX_BUFFERS_PER_COMMAND;
+		*iter_last_page_size = PAGE_SIZE;
+	} else {
+		*iter_last_page_size = last_page_size;
+	}
+
+	ret = pin_user_pages_fast(first_page, requested_pages,
+				  !is_write ? FOLL_WRITE : 0,
+				  pages);
+	if (ret <= 0)
+		return -EFAULT;
+	if (ret < requested_pages)
+		*iter_last_page_size = PAGE_SIZE;
+
+	return ret;
+}
+
+/* Populate the call parameters, merging adjacent pages together */
+static void populate_rw_params(struct page **pages,
+			       int pages_count,
+			       unsigned long address,
+			       unsigned long address_end,
+			       unsigned long first_page,
+			       unsigned long last_page,
+			       unsigned int iter_last_page_size,
+			       int is_write,
+			       struct goldfish_pipe_command *command)
+{
+	/*
+	 * Process the first page separately - it's the only page that
+	 * needs special handling for its start address.
+	 */
+	unsigned long xaddr = page_to_phys(pages[0]);
+	unsigned long xaddr_prev = xaddr;
+	int buffer_idx = 0;
+	int i = 1;
+	int size_on_page = first_page == last_page
+			? (int)(address_end - address)
+			: (PAGE_SIZE - (address & ~PAGE_MASK));
+	command->rw_params.ptrs[0] = (u64)(xaddr | (address & ~PAGE_MASK));
+	command->rw_params.sizes[0] = size_on_page;
+	for (; i < pages_count; ++i) {
+		xaddr = page_to_phys(pages[i]);
+		size_on_page = (i == pages_count - 1) ?
+			iter_last_page_size : PAGE_SIZE;
+		if (xaddr == xaddr_prev + PAGE_SIZE) {
+			command->rw_params.sizes[buffer_idx] += size_on_page;
+		} else {
+			++buffer_idx;
+			command->rw_params.ptrs[buffer_idx] = (u64)xaddr;
+			command->rw_params.sizes[buffer_idx] = size_on_page;
+		}
+		xaddr_prev = xaddr;
+	}
+	command->rw_params.buffers_count = buffer_idx + 1;
+}
+
+static int transfer_max_buffers(struct goldfish_pipe *pipe,
+				unsigned long address,
+				unsigned long address_end,
+				int is_write,
+				unsigned long last_page,
+				unsigned int last_page_size,
+				s32 *consumed_size,
+				int *status)
+{
+	unsigned long first_page = address & PAGE_MASK;
+	unsigned int iter_last_page_size;
+	int pages_count;
+
+	/* Serialize access to the pipe command buffers */
+	if (mutex_lock_interruptible(&pipe->lock))
+		return -ERESTARTSYS;
+
+	pages_count = goldfish_pin_pages(first_page, last_page,
+					 last_page_size, is_write,
+					 pipe->pages, &iter_last_page_size);
+	if (pages_count < 0) {
+		mutex_unlock(&pipe->lock);
+		return pages_count;
+	}
+
+	populate_rw_params(pipe->pages, pages_count, address, address_end,
+			   first_page, last_page, iter_last_page_size, is_write,
+			   pipe->command_buffer);
+
+	/* Transfer the data */
+	*status = goldfish_pipe_cmd_locked(pipe,
+				is_write ? PIPE_CMD_WRITE : PIPE_CMD_READ);
+
+	*consumed_size = pipe->command_buffer->rw_params.consumed_size;
+
+	unpin_user_pages_dirty_lock(pipe->pages, pages_count,
+				    !is_write && *consumed_size > 0);
+
+	mutex_unlock(&pipe->lock);
+	return 0;
+}
+
+static int wait_for_host_signal(struct goldfish_pipe *pipe, int is_write)
+{
+	u32 wake_bit = is_write ? BIT_WAKE_ON_WRITE : BIT_WAKE_ON_READ;
+
+	set_bit(wake_bit, &pipe->flags);
+
+	/* Tell the emulator we're going to wait for a wake event */
+	goldfish_pipe_cmd(pipe,
+		is_write ? PIPE_CMD_WAKE_ON_WRITE : PIPE_CMD_WAKE_ON_READ);
+
+	while (test_bit(wake_bit, &pipe->flags)) {
+		if (wait_event_interruptible(pipe->wake_queue,
+					     !test_bit(wake_bit, &pipe->flags)))
+			return -ERESTARTSYS;
+
+		if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
+			return -EIO;
+	}
+
+	return 0;
+}
+
+static ssize_t goldfish_pipe_read_write(struct file *filp,
+					char __user *buffer,
+					size_t bufflen,
+					int is_write)
+{
+	struct goldfish_pipe *pipe = filp->private_data;
+	int count = 0, ret = -EINVAL;
+	unsigned long address, address_end, last_page;
+	unsigned int last_page_size;
+
+	/* If the emulator already closed the pipe, no need to go further */
+	if (unlikely(test_bit(BIT_CLOSED_ON_HOST, &pipe->flags)))
+		return -EIO;
+	/* Null reads or writes succeeds */
+	if (unlikely(bufflen == 0))
+		return 0;
+	/* Check the buffer range for access */
+	if (unlikely(!access_ok(buffer, bufflen)))
+		return -EFAULT;
+
+	address = (unsigned long)buffer;
+	address_end = address + bufflen;
+	last_page = (address_end - 1) & PAGE_MASK;
+	last_page_size = ((address_end - 1) & ~PAGE_MASK) + 1;
+
+	while (address < address_end) {
+		s32 consumed_size;
+		int status;
+
+		ret = transfer_max_buffers(pipe, address, address_end, is_write,
+					   last_page, last_page_size,
+					   &consumed_size, &status);
+		if (ret < 0)
+			break;
+
+		if (consumed_size > 0) {
+			/* No matter what's the status, we've transferred
+			 * something.
+			 */
+			count += consumed_size;
+			address += consumed_size;
+		}
+		if (status > 0)
+			continue;
+		if (status == 0) {
+			/* EOF */
+			ret = 0;
+			break;
+		}
+		if (count > 0) {
+			/*
+			 * An error occurred, but we already transferred
+			 * something on one of the previous iterations.
+			 * Just return what we already copied and log this
+			 * err.
+			 */
+			if (status != PIPE_ERROR_AGAIN)
+				dev_err_ratelimited(pipe->dev->pdev_dev,
+					"backend error %d on %s\n",
+					status, is_write ? "write" : "read");
+			break;
+		}
+
+		/*
+		 * If the error is not PIPE_ERROR_AGAIN, or if we are in
+		 * non-blocking mode, just return the error code.
+		 */
+		if (status != PIPE_ERROR_AGAIN ||
+			(filp->f_flags & O_NONBLOCK) != 0) {
+			ret = goldfish_pipe_error_convert(status);
+			break;
+		}
+
+		status = wait_for_host_signal(pipe, is_write);
+		if (status < 0)
+			return status;
+	}
+
+	if (count > 0)
+		return count;
+	return ret;
+}
+
+static ssize_t goldfish_pipe_read(struct file *filp, char __user *buffer,
+				  size_t bufflen, loff_t *ppos)
+{
+	return goldfish_pipe_read_write(filp, buffer, bufflen,
+					/* is_write */ 0);
+}
+
+static ssize_t goldfish_pipe_write(struct file *filp,
+				   const char __user *buffer, size_t bufflen,
+				   loff_t *ppos)
+{
+	/* cast away the const */
+	char __user *no_const_buffer = (char __user *)buffer;
+
+	return goldfish_pipe_read_write(filp, no_const_buffer, bufflen,
+					/* is_write */ 1);
+}
+
+static __poll_t goldfish_pipe_poll(struct file *filp, poll_table *wait)
+{
+	struct goldfish_pipe *pipe = filp->private_data;
+	__poll_t mask = 0;
+	int status;
+
+	poll_wait(filp, &pipe->wake_queue, wait);
+
+	status = goldfish_pipe_cmd(pipe, PIPE_CMD_POLL);
+	if (status < 0)
+		return -ERESTARTSYS;
+
+	if (status & PIPE_POLL_IN)
+		mask |= EPOLLIN | EPOLLRDNORM;
+	if (status & PIPE_POLL_OUT)
+		mask |= EPOLLOUT | EPOLLWRNORM;
+	if (status & PIPE_POLL_HUP)
+		mask |= EPOLLHUP;
+	if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
+		mask |= EPOLLERR;
+
+	return mask;
+}
+
+static void signalled_pipes_add_locked(struct goldfish_pipe_dev *dev,
+				       u32 id, u32 flags)
+{
+	struct goldfish_pipe *pipe;
+
+	if (WARN_ON(id >= dev->pipes_capacity))
+		return;
+
+	pipe = dev->pipes[id];
+	if (!pipe)
+		return;
+	pipe->signalled_flags |= flags;
+
+	if (pipe->prev_signalled || pipe->next_signalled ||
+		dev->first_signalled_pipe == pipe)
+		return;	/* already in the list */
+	pipe->next_signalled = dev->first_signalled_pipe;
+	if (dev->first_signalled_pipe)
+		dev->first_signalled_pipe->prev_signalled = pipe;
+	dev->first_signalled_pipe = pipe;
+}
+
+static void signalled_pipes_remove_locked(struct goldfish_pipe_dev *dev,
+					  struct goldfish_pipe *pipe)
+{
+	if (pipe->prev_signalled)
+		pipe->prev_signalled->next_signalled = pipe->next_signalled;
+	if (pipe->next_signalled)
+		pipe->next_signalled->prev_signalled = pipe->prev_signalled;
+	if (pipe == dev->first_signalled_pipe)
+		dev->first_signalled_pipe = pipe->next_signalled;
+	pipe->prev_signalled = NULL;
+	pipe->next_signalled = NULL;
+}
+
+static struct goldfish_pipe *signalled_pipes_pop_front(
+		struct goldfish_pipe_dev *dev, int *wakes)
+{
+	struct goldfish_pipe *pipe;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+
+	pipe = dev->first_signalled_pipe;
+	if (pipe) {
+		*wakes = pipe->signalled_flags;
+		pipe->signalled_flags = 0;
+		/*
+		 * This is an optimized version of
+		 * signalled_pipes_remove_locked()
+		 * - We want to make it as fast as possible to
+		 * wake the sleeping pipe operations faster.
+		 */
+		dev->first_signalled_pipe = pipe->next_signalled;
+		if (dev->first_signalled_pipe)
+			dev->first_signalled_pipe->prev_signalled = NULL;
+		pipe->next_signalled = NULL;
+	}
+
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return pipe;
+}
+
+static irqreturn_t goldfish_interrupt_task(int irq, void *dev_addr)
+{
+	/* Iterate over the signalled pipes and wake them one by one */
+	struct goldfish_pipe_dev *dev = dev_addr;
+	struct goldfish_pipe *pipe;
+	int wakes;
+
+	while ((pipe = signalled_pipes_pop_front(dev, &wakes)) != NULL) {
+		if (wakes & PIPE_WAKE_CLOSED) {
+			pipe->flags = 1 << BIT_CLOSED_ON_HOST;
+		} else {
+			if (wakes & PIPE_WAKE_READ)
+				clear_bit(BIT_WAKE_ON_READ, &pipe->flags);
+			if (wakes & PIPE_WAKE_WRITE)
+				clear_bit(BIT_WAKE_ON_WRITE, &pipe->flags);
+		}
+		/*
+		 * wake_up_interruptible() implies a write barrier, so don't
+		 * explicitly add another one here.
+		 */
+		wake_up_interruptible(&pipe->wake_queue);
+	}
+	return IRQ_HANDLED;
+}
+
+static void goldfish_pipe_device_deinit(struct platform_device *pdev,
+					struct goldfish_pipe_dev *dev);
+
+/*
+ * The general idea of the (threaded) interrupt handling:
+ *
+ *  1. device raises an interrupt if there's at least one signalled pipe
+ *  2. IRQ handler reads the signalled pipes and their count from the device
+ *  3. device writes them into a shared buffer and returns the count
+ *      it only resets the IRQ if it has returned all signalled pipes,
+ *      otherwise it leaves it raised, so IRQ handler will be called
+ *      again for the next chunk
+ *  4. IRQ handler adds all returned pipes to the device's signalled pipes list
+ *  5. IRQ handler defers processing the signalled pipes from the list in a
+ *      separate context
+ */
+static irqreturn_t goldfish_pipe_interrupt(int irq, void *dev_id)
+{
+	u32 count;
+	u32 i;
+	unsigned long flags;
+	struct goldfish_pipe_dev *dev = dev_id;
+
+	if (dev->magic != &goldfish_pipe_device_deinit)
+		return IRQ_NONE;
+
+	/* Request the signalled pipes from the device */
+	spin_lock_irqsave(&dev->lock, flags);
+
+	count = readl(dev->base + PIPE_REG_GET_SIGNALLED);
+	if (count == 0) {
+		spin_unlock_irqrestore(&dev->lock, flags);
+		return IRQ_NONE;
+	}
+	if (count > MAX_SIGNALLED_PIPES)
+		count = MAX_SIGNALLED_PIPES;
+
+	for (i = 0; i < count; ++i)
+		signalled_pipes_add_locked(dev,
+			dev->buffers->signalled_pipe_buffers[i].id,
+			dev->buffers->signalled_pipe_buffers[i].flags);
+
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	return IRQ_WAKE_THREAD;
+}
+
+static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev)
+{
+	int id;
+
+	for (id = 0; id < dev->pipes_capacity; ++id)
+		if (!dev->pipes[id])
+			return id;
+
+	{
+		/* Reallocate the array.
+		 * Since get_free_pipe_id_locked runs with interrupts disabled,
+		 * we don't want to make calls that could lead to sleep.
+		 */
+		u32 new_capacity = 2 * dev->pipes_capacity;
+		struct goldfish_pipe **pipes =
+			kcalloc(new_capacity, sizeof(*pipes), GFP_ATOMIC);
+		if (!pipes)
+			return -ENOMEM;
+		memcpy(pipes, dev->pipes, sizeof(*pipes) * dev->pipes_capacity);
+		kfree(dev->pipes);
+		dev->pipes = pipes;
+		id = dev->pipes_capacity;
+		dev->pipes_capacity = new_capacity;
+	}
+	return id;
+}
+
+/* A helper function to get the instance of goldfish_pipe_dev from file */
+static struct goldfish_pipe_dev *to_goldfish_pipe_dev(struct file *file)
+{
+	struct miscdevice *miscdev = file->private_data;
+
+	return container_of(miscdev, struct goldfish_pipe_dev, miscdev);
+}
+
+/**
+ *	goldfish_pipe_open - open a channel to the AVD
+ *	@inode: inode of device
+ *	@file: file struct of opener
+ *
+ *	Create a new pipe link between the emulator and the use application.
+ *	Each new request produces a new pipe.
+ *
+ *	Note: we use the pipe ID as a mux. All goldfish emulations are 32bit
+ *	right now so this is fine. A move to 64bit will need this addressing
+ */
+static int goldfish_pipe_open(struct inode *inode, struct file *file)
+{
+	struct goldfish_pipe_dev *dev = to_goldfish_pipe_dev(file);
+	unsigned long flags;
+	int id;
+	int status;
+
+	/* Allocate new pipe kernel object */
+	struct goldfish_pipe *pipe = kzalloc(sizeof(*pipe), GFP_KERNEL);
+
+	if (!pipe)
+		return -ENOMEM;
+
+	pipe->dev = dev;
+	mutex_init(&pipe->lock);
+	init_waitqueue_head(&pipe->wake_queue);
+
+	/*
+	 * Command buffer needs to be allocated on its own page to make sure
+	 * it is physically contiguous in host's address space.
+	 */
+	BUILD_BUG_ON(sizeof(struct goldfish_pipe_command) > PAGE_SIZE);
+	pipe->command_buffer =
+		(struct goldfish_pipe_command *)__get_free_page(GFP_KERNEL);
+	if (!pipe->command_buffer) {
+		status = -ENOMEM;
+		goto err_pipe;
+	}
+
+	spin_lock_irqsave(&dev->lock, flags);
+
+	id = get_free_pipe_id_locked(dev);
+	if (id < 0) {
+		status = id;
+		goto err_id_locked;
+	}
+
+	dev->pipes[id] = pipe;
+	pipe->id = id;
+	pipe->command_buffer->id = id;
+
+	/* Now tell the emulator we're opening a new pipe. */
+	dev->buffers->open_command_params.rw_params_max_count =
+			MAX_BUFFERS_PER_COMMAND;
+	dev->buffers->open_command_params.command_buffer_ptr =
+			(u64)(unsigned long)__pa(pipe->command_buffer);
+	status = goldfish_pipe_cmd_locked(pipe, PIPE_CMD_OPEN);
+	spin_unlock_irqrestore(&dev->lock, flags);
+	if (status < 0)
+		goto err_cmd;
+	/* All is done, save the pipe into the file's private data field */
+	file->private_data = pipe;
+	return 0;
+
+err_cmd:
+	spin_lock_irqsave(&dev->lock, flags);
+	dev->pipes[id] = NULL;
+err_id_locked:
+	spin_unlock_irqrestore(&dev->lock, flags);
+	free_page((unsigned long)pipe->command_buffer);
+err_pipe:
+	kfree(pipe);
+	return status;
+}
+
+static int goldfish_pipe_release(struct inode *inode, struct file *filp)
+{
+	unsigned long flags;
+	struct goldfish_pipe *pipe = filp->private_data;
+	struct goldfish_pipe_dev *dev = pipe->dev;
+
+	/* The guest is closing the channel, so tell the emulator right now */
+	goldfish_pipe_cmd(pipe, PIPE_CMD_CLOSE);
+
+	spin_lock_irqsave(&dev->lock, flags);
+	dev->pipes[pipe->id] = NULL;
+	signalled_pipes_remove_locked(dev, pipe);
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	filp->private_data = NULL;
+	free_page((unsigned long)pipe->command_buffer);
+	kfree(pipe);
+	return 0;
+}
+
+static const struct file_operations goldfish_pipe_fops = {
+	.owner = THIS_MODULE,
+	.read = goldfish_pipe_read,
+	.write = goldfish_pipe_write,
+	.poll = goldfish_pipe_poll,
+	.open = goldfish_pipe_open,
+	.release = goldfish_pipe_release,
+};
+
+static void init_miscdevice(struct miscdevice *miscdev)
+{
+	memset(miscdev, 0, sizeof(*miscdev));
+
+	miscdev->minor = MISC_DYNAMIC_MINOR;
+	miscdev->name = "goldfish_pipe";
+	miscdev->fops = &goldfish_pipe_fops;
+}
+
+static void write_pa_addr(void *addr, void __iomem *portl, void __iomem *porth)
+{
+	const unsigned long paddr = __pa(addr);
+
+	writel(upper_32_bits(paddr), porth);
+	writel(lower_32_bits(paddr), portl);
+}
+
+static int goldfish_pipe_device_init(struct platform_device *pdev,
+				     struct goldfish_pipe_dev *dev)
+{
+	int err;
+
+	err = devm_request_threaded_irq(&pdev->dev, dev->irq,
+					goldfish_pipe_interrupt,
+					goldfish_interrupt_task,
+					IRQF_SHARED, "goldfish_pipe", dev);
+	if (err) {
+		dev_err(&pdev->dev, "unable to allocate IRQ for v2\n");
+		return err;
+	}
+
+	init_miscdevice(&dev->miscdev);
+	err = misc_register(&dev->miscdev);
+	if (err) {
+		dev_err(&pdev->dev, "unable to register v2 device\n");
+		return err;
+	}
+
+	dev->pdev_dev = &pdev->dev;
+	dev->first_signalled_pipe = NULL;
+	dev->pipes_capacity = INITIAL_PIPES_CAPACITY;
+	dev->pipes = kcalloc(dev->pipes_capacity, sizeof(*dev->pipes),
+			     GFP_KERNEL);
+	if (!dev->pipes) {
+		misc_deregister(&dev->miscdev);
+		return -ENOMEM;
+	}
+
+	/*
+	 * We're going to pass two buffers, open_command_params and
+	 * signalled_pipe_buffers, to the host. This means each of those buffers
+	 * needs to be contained in a single physical page. The easiest choice
+	 * is to just allocate a page and place the buffers in it.
+	 */
+	BUILD_BUG_ON(sizeof(struct goldfish_pipe_dev_buffers) > PAGE_SIZE);
+	dev->buffers = (struct goldfish_pipe_dev_buffers *)
+		__get_free_page(GFP_KERNEL);
+	if (!dev->buffers) {
+		kfree(dev->pipes);
+		misc_deregister(&dev->miscdev);
+		return -ENOMEM;
+	}
+
+	/* Send the buffer addresses to the host */
+	write_pa_addr(&dev->buffers->signalled_pipe_buffers,
+		      dev->base + PIPE_REG_SIGNAL_BUFFER,
+		      dev->base + PIPE_REG_SIGNAL_BUFFER_HIGH);
+
+	writel(MAX_SIGNALLED_PIPES,
+	       dev->base + PIPE_REG_SIGNAL_BUFFER_COUNT);
+
+	write_pa_addr(&dev->buffers->open_command_params,
+		      dev->base + PIPE_REG_OPEN_BUFFER,
+		      dev->base + PIPE_REG_OPEN_BUFFER_HIGH);
+
+	platform_set_drvdata(pdev, dev);
+	return 0;
+}
+
+static void goldfish_pipe_device_deinit(struct platform_device *pdev,
+					struct goldfish_pipe_dev *dev)
+{
+	misc_deregister(&dev->miscdev);
+	kfree(dev->pipes);
+	free_page((unsigned long)dev->buffers);
+}
+
+static int goldfish_pipe_probe(struct platform_device *pdev)
+{
+	struct resource *r;
+	struct goldfish_pipe_dev *dev;
+
+	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	dev->magic = &goldfish_pipe_device_deinit;
+	spin_lock_init(&dev->lock);
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!r || resource_size(r) < PAGE_SIZE) {
+		dev_err(&pdev->dev, "can't allocate i/o page\n");
+		return -EINVAL;
+	}
+	dev->base = devm_ioremap(&pdev->dev, r->start, PAGE_SIZE);
+	if (!dev->base) {
+		dev_err(&pdev->dev, "ioremap failed\n");
+		return -EINVAL;
+	}
+
+	dev->irq = platform_get_irq(pdev, 0);
+	if (dev->irq < 0)
+		return dev->irq;
+
+	/*
+	 * Exchange the versions with the host device
+	 *
+	 * Note: v1 driver used to not report its version, so we write it before
+	 *  reading device version back: this allows the host implementation to
+	 *  detect the old driver (if there was no version write before read).
+	 */
+	writel(PIPE_DRIVER_VERSION, dev->base + PIPE_REG_VERSION);
+	dev->version = readl(dev->base + PIPE_REG_VERSION);
+	if (WARN_ON(dev->version < PIPE_CURRENT_DEVICE_VERSION))
+		return -EINVAL;
+
+	return goldfish_pipe_device_init(pdev, dev);
+}
+
+static int goldfish_pipe_remove(struct platform_device *pdev)
+{
+	struct goldfish_pipe_dev *dev = platform_get_drvdata(pdev);
+
+	goldfish_pipe_device_deinit(pdev, dev);
+	return 0;
+}
+
+static const struct acpi_device_id goldfish_pipe_acpi_match[] = {
+	{ "GFSH0003", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, goldfish_pipe_acpi_match);
+
+static const struct of_device_id goldfish_pipe_of_match[] = {
+	{ .compatible = "google,android-pipe", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, goldfish_pipe_of_match);
+
+static struct platform_driver goldfish_pipe_driver = {
+	.probe = goldfish_pipe_probe,
+	.remove = goldfish_pipe_remove,
+	.driver = {
+		.name = "goldfish_pipe",
+		.of_match_table = goldfish_pipe_of_match,
+		.acpi_match_table = ACPI_PTR(goldfish_pipe_acpi_match),
+	}
+};
+
+module_platform_driver(goldfish_pipe_driver);
+MODULE_AUTHOR("David Turner <digit@google.com>");
+MODULE_LICENSE("GPL v2");