goldfish: add QEMU pipe driver

A QEMU pipe is a very fast communication channel between the
guest system and the emulator. Usage from the guest is simply
something like;

  // connect to special device
  fd = open("/dev/qemu_pipe", O_RDWR);

  // tell which service we want to talk to (must be zero-terminated)
  write(fd, "pipeName", strlen("pipeName")+1);

  // do read()/write() through fd now
  ...

  // close channel
  close(fd);
Signed-off-by: NDavid 'Digit' Turner <digit@android.com>
[Added support for parameter buffers for speed]
igned-off-by: NXin, Xiaohui <xiaohui.xin@intel.com>
Signed-off-by: NJiang, Yunhong <yunhong.jiang@intel.com>
Signed-off-by: NNakajima, Jun <jun.nakajima@intel.com>
[Ported to 3.6]
Signed-off-by: NTom Keel <thomas.keel@intel.com>
[Ported to 3.7, moved to platform/goldfish]
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/platform/Kconfig

 if X86
 source "drivers/platform/x86/Kconfig"
 endif
+if GOLDFISH
+source "drivers/platform/goldfish/Kconfig"
+endif
+

drivers/platform/goldfish/Kconfig

+config GOLDFISH_PIPE
+	tristate "Goldfish virtual device for QEMU pipes"
+	---help---
+	  This is a virtual device to drive the QEMU pipe interface used by
+	  the Goldfish Android Virtual Device.

drivers/platform/goldfish/Makefile

@@ -2,3 +2,4 @@
 # Makefile for Goldfish platform specific drivers
 #
 obj-$(CONFIG_GOLDFISH)	+=	pdev_bus.o
+obj-$(CONFIG_GOLDFISH_PIPE)	+= goldfish_pipe.o

drivers/platform/goldfish/goldfish_pipe.c

+/*
+ * Copyright (C) 2011 Google, Inc.
+ * Copyright (C) 2012 Intel, Inc.
+ * Copyright (C) 2013 Intel, 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/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>
+
+/*
+ * IMPORTANT: The following constants must match the ones used and defined
+ * in external/qemu/hw/goldfish_pipe.c in the Android source tree.
+ */
+
+/* pipe device registers */
+#define PIPE_REG_COMMAND		0x00  /* write: value = command */
+#define PIPE_REG_STATUS			0x04  /* read */
+#define PIPE_REG_CHANNEL		0x08  /* read/write: channel id */
+#define PIPE_REG_SIZE			0x0c  /* read/write: buffer size */
+#define PIPE_REG_ADDRESS		0x10  /* write: physical address */
+#define PIPE_REG_WAKES			0x14  /* read: wake flags */
+#define PIPE_REG_PARAMS_ADDR_LOW	0x18  /* read/write: batch data address */
+#define PIPE_REG_PARAMS_ADDR_HIGH	0x1c  /* read/write: batch data address */
+#define PIPE_REG_ACCESS_PARAMS		0x20  /* write: batch access */
+
+/* list of commands for PIPE_REG_COMMAND */
+#define CMD_OPEN			1  /* open new channel */
+#define CMD_CLOSE			2  /* close channel (from guest) */
+#define CMD_POLL			3  /* poll read/write status */
+
+/* List of bitflags returned in status of CMD_POLL command */
+#define PIPE_POLL_IN			(1 << 0)
+#define PIPE_POLL_OUT			(1 << 1)
+#define PIPE_POLL_HUP			(1 << 2)
+
+/* The following commands are related to write operations */
+#define CMD_WRITE_BUFFER	4  /* send a user buffer to the emulator */
+#define CMD_WAKE_ON_WRITE	5  /* tell the emulator to wake us when writing
+				     is possible */
+
+/* The following commands are related to read operations, they must be
+ * listed in the same order than the corresponding write ones, since we
+ * will use (CMD_READ_BUFFER - CMD_WRITE_BUFFER) as a special offset
+ * in goldfish_pipe_read_write() below.
+ */
+#define CMD_READ_BUFFER        6  /* receive a user buffer from the emulator */
+#define CMD_WAKE_ON_READ       7  /* tell the emulator to wake us when reading
+				   * is possible */
+
+/* Possible status values used to signal errors - see goldfish_pipe_error_convert */
+#define PIPE_ERROR_INVAL       -1
+#define PIPE_ERROR_AGAIN       -2
+#define PIPE_ERROR_NOMEM       -3
+#define PIPE_ERROR_IO          -4
+
+/* Bit-flags used to signal events from the emulator */
+#define PIPE_WAKE_CLOSED       (1 << 0)  /* emulator closed pipe */
+#define PIPE_WAKE_READ         (1 << 1)  /* pipe can now be read from */
+#define PIPE_WAKE_WRITE        (1 << 2)  /* pipe can now be written to */
+
+struct access_params {
+	u32 channel;
+	u32 size;
+	u32 address;
+	u32 cmd;
+	u32 result;
+	/* reserved for future extension */
+	u32 flags;
+};
+
+/* 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 {
+	spinlock_t lock;
+	unsigned char __iomem *base;
+	struct access_params *aps;
+	int irq;
+};
+
+static struct goldfish_pipe_dev   pipe_dev[1];
+
+/* This data type models a given pipe instance */
+struct goldfish_pipe {
+	struct goldfish_pipe_dev *dev;
+	struct mutex lock;
+	unsigned long flags;
+	wait_queue_head_t wake_queue;
+};
+
+
+/* Bit flags for the 'flags' field */
+enum {
+	BIT_CLOSED_ON_HOST = 0,  /* pipe closed by host */
+	BIT_WAKE_ON_WRITE  = 1,  /* want to be woken on writes */
+	BIT_WAKE_ON_READ   = 2,  /* want to be woken on reads */
+};
+
+
+static u32 goldfish_cmd_status(struct goldfish_pipe *pipe, u32 cmd)
+{ 
+	unsigned long flags;
+	u32 status;
+	struct goldfish_pipe_dev *dev = pipe->dev;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	writel((u32)pipe, dev->base + PIPE_REG_CHANNEL);
+	writel(cmd, dev->base + PIPE_REG_COMMAND);
+	status = readl(dev->base + PIPE_REG_STATUS);
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return status;
+}
+
+static void goldfish_cmd(struct goldfish_pipe *pipe, u32 cmd)
+{ 
+	unsigned long flags;
+	struct goldfish_pipe_dev *dev = pipe->dev;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	writel((u32)pipe, dev->base + PIPE_REG_CHANNEL);
+	writel(cmd, dev->base + PIPE_REG_COMMAND);
+	spin_unlock_irqrestore(&dev->lock, flags);
+}
+
+/* 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;
+	}
+}
+
+/*
+ * Notice: QEMU will return 0 for un-known register access, indicating
+ * param_acess is supported or not
+ */
+static int valid_batchbuffer_addr(struct goldfish_pipe_dev *dev,
+				  struct access_params *aps)
+{
+	u32 aph, apl;
+	u64 paddr;
+	aph = readl(dev->base + PIPE_REG_PARAMS_ADDR_HIGH);
+	apl = readl(dev->base + PIPE_REG_PARAMS_ADDR_LOW);
+
+	paddr = ((u64)aph << 32) | apl;
+	if (paddr != (__pa(aps)))
+		return 0;
+	return 1;
+}
+
+/* 0 on success */
+static int setup_access_params_addr(struct platform_device *pdev,
+					struct goldfish_pipe_dev *dev)
+{
+	u64 paddr;
+	struct access_params *aps;
+
+	aps = devm_kzalloc(&pdev->dev, sizeof(struct access_params), GFP_KERNEL);
+	if (!aps)
+		return -1;
+
+	/* FIXME */
+	paddr = __pa(aps);
+	writel((u32)(paddr >> 32), dev->base + PIPE_REG_PARAMS_ADDR_HIGH);
+	writel((u32)paddr, dev->base + PIPE_REG_PARAMS_ADDR_LOW);
+
+	if (valid_batchbuffer_addr(dev, aps)) {
+		dev->aps = aps;
+		return 0;
+	} else
+		return -1;
+}
+
+/* A value that will not be set by qemu emulator */
+#define INITIAL_BATCH_RESULT (0xdeadbeaf)
+static int access_with_param(struct goldfish_pipe_dev *dev, const int cmd,
+				unsigned long address, unsigned long avail,
+				struct goldfish_pipe *pipe, int *status)
+{
+	struct access_params *aps = dev->aps;
+
+	if (aps == NULL)
+		return -1;
+
+	aps->result = INITIAL_BATCH_RESULT;
+	aps->channel = (unsigned long)pipe;
+	aps->size = avail;
+	aps->address = address;
+	aps->cmd = cmd;
+	writel(cmd, dev->base + PIPE_REG_ACCESS_PARAMS);
+	/*
+	 * If the aps->result has not changed, that means
+	 * that the batch command failed
+	 */
+	if (aps->result == INITIAL_BATCH_RESULT)
+		return -1;
+	*status = aps->result;
+	return 0;
+}
+
+/* This function is used for both reading from and writing to a given
+ * pipe.
+ */
+static ssize_t goldfish_pipe_read_write(struct file *filp, char __user *buffer,
+				    size_t bufflen, int is_write)
+{
+	unsigned long irq_flags;
+	struct goldfish_pipe *pipe = filp->private_data;
+	struct goldfish_pipe_dev *dev = pipe->dev;
+	const int cmd_offset = is_write ? 0
+					: (CMD_READ_BUFFER - CMD_WRITE_BUFFER);
+	unsigned long address, address_end;
+	int ret = 0;
+
+	/* If the emulator already closed the pipe, no need to go further */
+	if (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 (!access_ok(is_write ? VERIFY_WRITE : VERIFY_READ,
+			buffer, bufflen))
+		return -EFAULT;
+
+	/* Serialize access to the pipe */
+	if (mutex_lock_interruptible(&pipe->lock))
+		return -ERESTARTSYS;
+
+	address = (unsigned long)(void *)buffer;
+	address_end = address + bufflen;
+
+	while (address < address_end) {
+		unsigned long  page_end = (address & PAGE_MASK) + PAGE_SIZE;
+		unsigned long  next     = page_end < address_end ? page_end
+								 : address_end;
+		unsigned long  avail    = next - address;
+		int status, wakeBit;
+
+		/* Ensure that the corresponding page is properly mapped */
+		if (is_write) {
+			char c;
+			/* Ensure that the page is mapped and readable */
+			if (__get_user(c, (char __user *)address)) {
+				if (!ret)
+					ret = -EFAULT;
+				break;
+			}
+		} else {
+			/* Ensure that the page is mapped and writable */
+			if (__put_user(0, (char __user *)address)) {
+				if (!ret)
+					ret = -EFAULT;
+				break;
+			}
+		}
+
+		/* Now, try to transfer the bytes in the current page */
+		spin_lock_irqsave(&dev->lock, irq_flags);
+		if (access_with_param(dev, CMD_WRITE_BUFFER + cmd_offset,
+				address, avail, pipe, &status)) {
+			writel((u32)pipe, dev->base + PIPE_REG_CHANNEL);
+			writel(avail, dev->base + PIPE_REG_SIZE);
+			writel(address, dev->base + PIPE_REG_ADDRESS);
+			writel(CMD_WRITE_BUFFER + cmd_offset,
+					dev->base + PIPE_REG_COMMAND);
+			status = readl(dev->base + PIPE_REG_STATUS);
+		}
+		spin_unlock_irqrestore(&dev->lock, irq_flags);
+
+		if (status > 0) { /* Correct transfer */
+			ret += status;
+			address += status;
+			continue;
+		}
+
+		if (status == 0)  /* EOF */
+			break;
+
+		/* An error occured. If we already transfered stuff, just
+		* return with its count. We expect the next call to return
+		* an error code */
+		if (ret > 0)
+			break;
+
+		/* If the error is not PIPE_ERROR_AGAIN, or if we are not 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;
+		}
+
+		/* We will have to wait until more data/space is available.
+		* First, mark the pipe as waiting for a specific wake signal.
+		*/
+		wakeBit = is_write ? BIT_WAKE_ON_WRITE : BIT_WAKE_ON_READ;
+		set_bit(wakeBit, &pipe->flags);
+
+		/* Tell the emulator we're going to wait for a wake event */
+		goldfish_cmd(pipe, CMD_WAKE_ON_WRITE + cmd_offset);
+
+		/* Unlock the pipe, then wait for the wake signal */
+		mutex_unlock(&pipe->lock);
+
+		while (test_bit(wakeBit, &pipe->flags)) {
+			if (wait_event_interruptible(
+					pipe->wake_queue,
+					!test_bit(wakeBit, &pipe->flags)))
+				return -ERESTARTSYS;
+
+			if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
+				return -EIO;
+		}
+
+		/* Try to re-acquire the lock */
+		if (mutex_lock_interruptible(&pipe->lock))
+			return -ERESTARTSYS;
+
+		/* Try the transfer again */
+		continue;
+	}
+	mutex_unlock(&pipe->lock);
+	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, 0);
+}
+
+static ssize_t goldfish_pipe_write(struct file *filp,
+				const char __user *buffer, size_t bufflen,
+				loff_t *ppos)
+{
+	return goldfish_pipe_read_write(filp, (char __user *)buffer,
+								bufflen, 1);
+}
+
+
+static unsigned int goldfish_pipe_poll(struct file *filp, poll_table *wait)
+{
+	struct goldfish_pipe *pipe = filp->private_data;
+	unsigned int mask = 0;
+	int status;
+
+	mutex_lock(&pipe->lock);
+
+	poll_wait(filp, &pipe->wake_queue, wait);
+
+	status = goldfish_cmd_status(pipe, CMD_POLL);
+
+	mutex_unlock(&pipe->lock);
+
+	if (status & PIPE_POLL_IN)
+		mask |= POLLIN | POLLRDNORM;
+
+	if (status & PIPE_POLL_OUT)
+		mask |= POLLOUT | POLLWRNORM;
+
+	if (status & PIPE_POLL_HUP)
+		mask |= POLLHUP;
+
+	if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
+		mask |= POLLERR;
+
+	return mask;
+}
+
+static irqreturn_t goldfish_pipe_interrupt(int irq, void *dev_id)
+{
+	struct goldfish_pipe_dev *dev = dev_id;
+	unsigned long irq_flags;
+	int count = 0;
+
+	/* We're going to read from the emulator a list of (channel,flags)
+	* pairs corresponding to the wake events that occured on each
+	* blocked pipe (i.e. channel).
+	*/
+	spin_lock_irqsave(&dev->lock, irq_flags);
+	for (;;) {
+		/* First read the channel, 0 means the end of the list */
+		struct goldfish_pipe *pipe;
+		unsigned long wakes;
+		unsigned long channel = readl(dev->base + PIPE_REG_CHANNEL);
+
+		if (channel == 0)
+			break;
+
+		/* Convert channel to struct pipe pointer + read wake flags */
+		wakes = readl(dev->base + PIPE_REG_WAKES);
+		pipe  = (struct goldfish_pipe *)(ptrdiff_t)channel;
+
+		/* Did the emulator just closed a pipe? */
+		if (wakes & PIPE_WAKE_CLOSED) {
+			set_bit(BIT_CLOSED_ON_HOST, &pipe->flags);
+			wakes |= PIPE_WAKE_READ | PIPE_WAKE_WRITE;
+		}
+		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(&pipe->wake_queue);
+		count++;
+	}
+	spin_unlock_irqrestore(&dev->lock, irq_flags);
+
+	return (count == 0) ? IRQ_NONE : IRQ_HANDLED;
+}
+
+/**
+ *	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 *pipe;
+	struct goldfish_pipe_dev *dev = pipe_dev;
+	int32_t status;
+
+	/* Allocate new pipe kernel object */
+	pipe = kzalloc(sizeof(*pipe), GFP_KERNEL);
+	if (pipe == NULL)
+		return -ENOMEM;
+
+	pipe->dev = dev;
+	mutex_init(&pipe->lock);
+	init_waitqueue_head(&pipe->wake_queue);
+
+	/*
+	 * Now, tell the emulator we're opening a new pipe. We use the
+	 * pipe object's address as the channel identifier for simplicity.
+	 */
+
+	status = goldfish_cmd_status(pipe, CMD_OPEN);
+	if (status < 0) {
+		kfree(pipe);
+		return status;
+	}
+
+	/* All is done, save the pipe into the file's private data field */
+	file->private_data = pipe;
+	return 0;
+}
+
+static int goldfish_pipe_release(struct inode *inode, struct file *filp)
+{
+	struct goldfish_pipe *pipe = filp->private_data;
+
+	/* The guest is closing the channel, so tell the emulator right now */
+	goldfish_cmd(pipe, CMD_CLOSE);
+	kfree(pipe);
+	filp->private_data = NULL;
+	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 struct miscdevice goldfish_pipe_device = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "goldfish_pipe",
+	.fops = &goldfish_pipe_fops,
+};
+
+static int goldfish_pipe_probe(struct platform_device *pdev)
+{
+	int err;
+	struct resource *r;
+	struct goldfish_pipe_dev *dev = pipe_dev;
+
+	/* not thread safe, but this should not happen */
+	WARN_ON(dev->base != NULL);
+
+	spin_lock_init(&dev->lock);
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (r == NULL || 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 == NULL) {
+		dev_err(&pdev->dev, "ioremap failed\n");
+		return -EINVAL;
+	}
+
+	r = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (r == NULL) {
+		err = -EINVAL;
+		goto error;
+	}
+	dev->irq = r->start;
+
+	err = devm_request_irq(&pdev->dev, dev->irq, goldfish_pipe_interrupt,
+				IRQF_SHARED, "goldfish_pipe", dev);
+	if (err) {
+		dev_err(&pdev->dev, "unable to allocate IRQ\n");
+		goto error;
+	}
+
+	err = misc_register(&goldfish_pipe_device);
+	if (err) {
+		dev_err(&pdev->dev, "unable to register device\n");
+		goto error;
+	}
+	setup_access_params_addr(pdev, dev);
+	return 0;
+
+error:
+	dev->base = NULL;
+	return err;
+}
+
+static int goldfish_pipe_remove(struct platform_device *pdev)
+{
+	struct goldfish_pipe_dev *dev = pipe_dev;
+	misc_deregister(&goldfish_pipe_device);
+	dev->base = NULL;
+	return 0;
+}
+
+static struct platform_driver goldfish_pipe = {
+	.probe = goldfish_pipe_probe,
+	.remove = goldfish_pipe_remove,
+	.driver = {
+		.name = "goldfish_pipe"
+	}
+};
+
+module_platform_driver(goldfish_pipe);
+MODULE_AUTHOR("David Turner <digit@google.com>");
+MODULE_LICENSE("GPL");