The Sample driver creates mdev device that simulates serial port over PCI
card.

Signed-off-by: Kirti Wankhede <kwankh...@nvidia.com>
Signed-off-by: Neo Jia <c...@nvidia.com>
Change-Id: I857f8f12f8b275f2498dfe8c628a5cdc7193b1b2
---
 Documentation/vfio-mdev/Makefile                 |   13 +
 Documentation/vfio-mdev/mtty.c                   | 1429 ++++++++++++++++++++++
 Documentation/vfio-mdev/vfio-mediated-device.txt |  104 +-
 3 files changed, 1544 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/vfio-mdev/Makefile
 create mode 100644 Documentation/vfio-mdev/mtty.c

diff --git a/Documentation/vfio-mdev/Makefile b/Documentation/vfio-mdev/Makefile
new file mode 100644
index 000000000000..a932edbe38eb
--- /dev/null
+++ b/Documentation/vfio-mdev/Makefile
@@ -0,0 +1,13 @@
+#
+# Makefile for mtty.c file
+#
+KERNEL_DIR:=/lib/modules/$(shell uname -r)/build
+
+obj-m:=mtty.o
+
+modules clean modules_install:
+       $(MAKE) -C $(KERNEL_DIR) SUBDIRS=$(PWD) $@
+
+default: modules
+
+module: modules
diff --git a/Documentation/vfio-mdev/mtty.c b/Documentation/vfio-mdev/mtty.c
new file mode 100644
index 000000000000..8ac321c4c8f1
--- /dev/null
+++ b/Documentation/vfio-mdev/mtty.c
@@ -0,0 +1,1429 @@
+/*
+ * Mediated virtual PCI serial host device driver
+ *
+ * Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
+ *     Author: Neo Jia <c...@nvidia.com>
+ *             Kirti Wankhede <kwankh...@nvidia.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Sample driver that creates mdev device that simulates serial port over PCI
+ * card.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/cdev.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/uuid.h>
+#include <linux/vfio.h>
+#include <linux/iommu.h>
+#include <linux/sysfs.h>
+#include <linux/ctype.h>
+#include <linux/file.h>
+#include <linux/mdev.h>
+#include <linux/pci.h>
+#include <linux/serial.h>
+#include <uapi/linux/serial_reg.h>
+/*
+ * #defines
+ */
+
+#define VERSION_STRING  "0.1"
+#define DRIVER_AUTHOR   "NVIDIA Corporation"
+
+#define MTTY_CLASS_NAME "mtty"
+
+#define MTTY_NAME       "mtty"
+
+#define MTTY_STRING_LEN                16
+
+#define MTTY_CONFIG_SPACE_SIZE  0xff
+#define MTTY_IO_BAR_SIZE        0x8
+#define MTTY_MMIO_BAR_SIZE      0x100000
+
+#define STORE_LE16(addr, val)   (*(u16 *)addr = val)
+#define STORE_LE32(addr, val)   (*(u32 *)addr = val)
+
+#define MAX_FIFO_SIZE   16
+
+#define CIRCULAR_BUF_INC_IDX(idx)    (idx = (idx + 1) & (MAX_FIFO_SIZE - 1))
+
+#define MTTY_VFIO_PCI_OFFSET_SHIFT   40
+
+#define MTTY_VFIO_PCI_OFFSET_TO_INDEX(off)   (off >> 
MTTY_VFIO_PCI_OFFSET_SHIFT)
+#define MTTY_VFIO_PCI_INDEX_TO_OFFSET(index) \
+                               ((u64)(index) << MTTY_VFIO_PCI_OFFSET_SHIFT)
+#define MTTY_VFIO_PCI_OFFSET_MASK    \
+                               (((u64)(1) << MTTY_VFIO_PCI_OFFSET_SHIFT) - 1)
+#define MAX_MTTYS      24
+
+/*
+ * Global Structures
+ */
+
+struct mtty_dev {
+       dev_t           vd_devt;
+       struct class    *vd_class;
+       struct cdev     vd_cdev;
+       struct idr      vd_idr;
+       struct device   dev;
+} mtty_dev;
+
+struct mdev_region_info {
+       u64 start;
+       u64 phys_start;
+       u32 size;
+       u64 vfio_offset;
+};
+
+#if defined(DEBUG_REGS)
+const char *wr_reg[] = {
+       "TX",
+       "IER",
+       "FCR",
+       "LCR",
+       "MCR",
+       "LSR",
+       "MSR",
+       "SCR"
+};
+
+const char *rd_reg[] = {
+       "RX",
+       "IER",
+       "IIR",
+       "LCR",
+       "MCR",
+       "LSR",
+       "MSR",
+       "SCR"
+};
+#endif
+
+/* loop back buffer */
+struct rxtx {
+       u8 fifo[MAX_FIFO_SIZE];
+       u8 head, tail;
+       u8 count;
+};
+
+struct serial_port {
+       u8 uart_reg[8];         /* 8 registers */
+       struct rxtx rxtx;       /* loop back buffer */
+       bool dlab;
+       bool overrun;
+       u16 divisor;
+       u8 fcr;                 /* FIFO control register */
+       u8 max_fifo_size;
+       u8 intr_trigger_level;  /* interrupt trigger level */
+};
+
+/* State of each mdev device */
+struct mdev_state {
+       int irq_fd;
+       struct file *intx_file;
+       struct file *msi_file;
+       int irq_index;
+       u8 *vconfig;
+       struct mutex ops_lock;
+       struct mdev_device *mdev;
+       struct mdev_region_info region_info[VFIO_PCI_NUM_REGIONS];
+       u32 bar_mask[VFIO_PCI_NUM_REGIONS];
+       struct list_head next;
+       struct serial_port s[2];
+       struct mutex rxtx_lock;
+       struct vfio_device_info dev_info;
+       int nr_ports;
+};
+
+struct mutex mdev_list_lock;
+struct list_head mdev_devices_list;
+
+static const struct file_operations vd_fops = {
+       .owner          = THIS_MODULE,
+};
+
+/* function prototypes */
+
+static int mtty_trigger_interrupt(uuid_le uuid);
+
+/* Helper functions */
+static struct mdev_state *find_mdev_state_by_uuid(uuid_le uuid)
+{
+       struct mdev_state *mds;
+
+       list_for_each_entry(mds, &mdev_devices_list, next) {
+               if (uuid_le_cmp(mds->mdev->uuid, uuid) == 0)
+                       return mds;
+       }
+
+       return NULL;
+}
+
+void dump_buffer(char *buf, uint32_t count)
+{
+#if defined(DEBUG)
+       int i;
+
+       pr_info("Buffer:\n");
+       for (i = 0; i < count; i++) {
+               pr_info("%2x ", *(buf + i));
+               if ((i + 1) % 16 == 0)
+                       pr_info("\n");
+       }
+#endif
+}
+
+static void mtty_create_config_space(struct mdev_state *mdev_state)
+{
+       /* PCI dev ID */
+       STORE_LE32((u32 *) &mdev_state->vconfig[0x0], 0x32534348);
+
+       /* Control: I/O+, Mem-, BusMaster- */
+       STORE_LE16((u16 *) &mdev_state->vconfig[0x4], 0x0001);
+
+       /* Status: capabilities list absent */
+       STORE_LE16((u16 *) &mdev_state->vconfig[0x6], 0x0200);
+
+       /* Rev ID */
+       mdev_state->vconfig[0x8] =  0x10;
+
+       /* programming interface class : 16550-compatible serial controller */
+       mdev_state->vconfig[0x9] =  0x02;
+
+       /* Sub class : 00 */
+       mdev_state->vconfig[0xa] =  0x00;
+
+       /* Base class : Simple Communication controllers */
+       mdev_state->vconfig[0xb] =  0x07;
+
+       /* base address registers */
+       /* BAR0: IO space */
+       STORE_LE32((u32 *) &mdev_state->vconfig[0x10], 0x000001);
+       mdev_state->bar_mask[0] = ~(MTTY_IO_BAR_SIZE) + 1;
+
+       if (mdev_state->nr_ports == 2) {
+               /* BAR1: IO space */
+               STORE_LE32((u32 *) &mdev_state->vconfig[0x14], 0x000001);
+               mdev_state->bar_mask[1] = ~(MTTY_IO_BAR_SIZE) + 1;
+       }
+
+       /* Subsystem ID */
+       STORE_LE32((u32 *) &mdev_state->vconfig[0x2c], 0x32534348);
+
+       mdev_state->vconfig[0x34] =  0x00;   /* Cap Ptr */
+       mdev_state->vconfig[0x3d] =  0x01;   /* interrupt pin (INTA#) */
+
+       /* Vendor specific data */
+       mdev_state->vconfig[0x40] =  0x23;
+       mdev_state->vconfig[0x43] =  0x80;
+       mdev_state->vconfig[0x44] =  0x23;
+       mdev_state->vconfig[0x48] =  0x23;
+       mdev_state->vconfig[0x4c] =  0x23;
+
+       mdev_state->vconfig[0x60] =  0x50;
+       mdev_state->vconfig[0x61] =  0x43;
+       mdev_state->vconfig[0x62] =  0x49;
+       mdev_state->vconfig[0x63] =  0x20;
+       mdev_state->vconfig[0x64] =  0x53;
+       mdev_state->vconfig[0x65] =  0x65;
+       mdev_state->vconfig[0x66] =  0x72;
+       mdev_state->vconfig[0x67] =  0x69;
+       mdev_state->vconfig[0x68] =  0x61;
+       mdev_state->vconfig[0x69] =  0x6c;
+       mdev_state->vconfig[0x6a] =  0x2f;
+       mdev_state->vconfig[0x6b] =  0x55;
+       mdev_state->vconfig[0x6c] =  0x41;
+       mdev_state->vconfig[0x6d] =  0x52;
+       mdev_state->vconfig[0x6e] =  0x54;
+}
+
+static void handle_pci_cfg_write(struct mdev_state *mdev_state, u16 offset,
+                                char *buf, u32 count)
+{
+       u32 cfg_addr, bar_mask, bar_index = 0;
+
+       switch (offset) {
+       case 0x04: /* device control */
+       case 0x06: /* device status */
+               /* do nothing */
+               break;
+       case 0x3c:  /* interrupt line */
+               mdev_state->vconfig[0x3c] = buf[0];
+               break;
+       case 0x3d:
+               /*
+                * Interrupt Pin is hardwired to INTA.
+                * This field is write protected by hardware
+                */
+               break;
+       case 0x10:  /* BAR0 */
+       case 0x14:  /* BAR1 */
+               if (offset == 0x10)
+                       bar_index = 0;
+               else if (offset == 0x14)
+                       bar_index = 1;
+
+               if ((mdev_state->nr_ports == 1) && (bar_index == 1)) {
+                       STORE_LE32(&mdev_state->vconfig[offset], 0);
+                       break;
+               }
+
+               cfg_addr = *(u32 *)buf;
+               pr_info("BAR%d addr 0x%x\n", bar_index, cfg_addr);
+
+               if (cfg_addr == 0xffffffff) {
+                       bar_mask = mdev_state->bar_mask[bar_index];
+                       cfg_addr = (cfg_addr & bar_mask);
+               }
+
+               cfg_addr |= (mdev_state->vconfig[offset] & 0x3ul);
+               STORE_LE32(&mdev_state->vconfig[offset], cfg_addr);
+               break;
+       case 0x18:  /* BAR2 */
+       case 0x1c:  /* BAR3 */
+       case 0x20:  /* BAR4 */
+               STORE_LE32(&mdev_state->vconfig[offset], 0);
+               break;
+       default:
+               pr_info("PCI config write @0x%x of %d bytes not handled\n",
+                       offset, count);
+               break;
+       }
+}
+
+static void handle_bar_write(unsigned int index, struct mdev_state *mdev_state,
+                               u16 offset, char *buf, u32 count)
+{
+       u8 data = *buf;
+
+       /* Handle data written by guest */
+       switch (offset) {
+       case UART_TX:
+               /* if DLAB set, data is LSB of divisor */
+               if (mdev_state->s[index].dlab) {
+                       mdev_state->s[index].divisor |= data;
+                       break;
+               }
+
+               mutex_lock(&mdev_state->rxtx_lock);
+
+               /* save in TX buffer */
+               if (mdev_state->s[index].rxtx.count <
+                               mdev_state->s[index].max_fifo_size) {
+                       mdev_state->s[index].rxtx.fifo[
+                                       mdev_state->s[index].rxtx.head] = data;
+                       mdev_state->s[index].rxtx.count++;
+                       CIRCULAR_BUF_INC_IDX(mdev_state->s[index].rxtx.head);
+                       mdev_state->s[index].overrun = false;
+
+                       /*
+                        * Trigger interrupt if receive data interrupt is
+                        * enabled and fifo reached trigger level
+                        */
+                       if ((mdev_state->s[index].uart_reg[UART_IER] &
+                                               UART_IER_RDI) &&
+                          (mdev_state->s[index].rxtx.count ==
+                                   mdev_state->s[index].intr_trigger_level)) {
+                               /* trigger interrupt */
+#if defined(DEBUG_INTR)
+                               pr_err("Serial port %d: Fifo level trigger\n",
+                                       index);
+#endif
+                               mtty_trigger_interrupt(mdev_state->mdev->uuid);
+                       }
+               } else {
+#if defined(DEBUG_INTR)
+                       pr_err("Serial port %d: Buffer Overflow\n", index);
+#endif
+                       mdev_state->s[index].overrun = true;
+
+                       /*
+                        * Trigger interrupt if receiver line status interrupt
+                        * is enabled
+                        */
+                       if (mdev_state->s[index].uart_reg[UART_IER] &
+                                                               UART_IER_RLSI)
+                               mtty_trigger_interrupt(mdev_state->mdev->uuid);
+               }
+               mutex_unlock(&mdev_state->rxtx_lock);
+               break;
+
+       case UART_IER:
+               /* if DLAB set, data is MSB of divisor */
+               if (mdev_state->s[index].dlab)
+                       mdev_state->s[index].divisor |= (u16)data << 8;
+               else {
+                       mdev_state->s[index].uart_reg[offset] = data;
+                       mutex_lock(&mdev_state->rxtx_lock);
+                       if ((data & UART_IER_THRI) &&
+                           (mdev_state->s[index].rxtx.head ==
+                                       mdev_state->s[index].rxtx.tail)) {
+#if defined(DEBUG_INTR)
+                               pr_err("Serial port %d: IER_THRI write\n",
+                                       index);
+#endif
+                               mtty_trigger_interrupt(mdev_state->mdev->uuid);
+                       }
+
+                       mutex_unlock(&mdev_state->rxtx_lock);
+               }
+
+               break;
+
+       case UART_FCR:
+               mdev_state->s[index].fcr = data;
+
+               mutex_lock(&mdev_state->rxtx_lock);
+               if (data & (UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT)) {
+                       /* clear loop back FIFO */
+                       mdev_state->s[index].rxtx.count = 0;
+                       mdev_state->s[index].rxtx.head = 0;
+                       mdev_state->s[index].rxtx.tail = 0;
+               }
+               mutex_unlock(&mdev_state->rxtx_lock);
+
+               switch (data & UART_FCR_TRIGGER_MASK) {
+               case UART_FCR_TRIGGER_1:
+                       mdev_state->s[index].intr_trigger_level = 1;
+                       break;
+
+               case UART_FCR_TRIGGER_4:
+                       mdev_state->s[index].intr_trigger_level = 4;
+                       break;
+
+               case UART_FCR_TRIGGER_8:
+                       mdev_state->s[index].intr_trigger_level = 8;
+                       break;
+
+               case UART_FCR_TRIGGER_14:
+                       mdev_state->s[index].intr_trigger_level = 14;
+                       break;
+               }
+
+               /*
+                * Set trigger level to 1 otherwise or  implement timer with
+                * timeout of 4 characters and on expiring that timer set
+                * Recevice data timeout in IIR register
+                */
+               mdev_state->s[index].intr_trigger_level = 1;
+               if (data & UART_FCR_ENABLE_FIFO)
+                       mdev_state->s[index].max_fifo_size = MAX_FIFO_SIZE;
+               else {
+                       mdev_state->s[index].max_fifo_size = 1;
+                       mdev_state->s[index].intr_trigger_level = 1;
+               }
+
+               break;
+
+       case UART_LCR:
+               if (data & UART_LCR_DLAB) {
+                       mdev_state->s[index].dlab = true;
+                       mdev_state->s[index].divisor = 0;
+               } else
+                       mdev_state->s[index].dlab = false;
+
+               mdev_state->s[index].uart_reg[offset] = data;
+               break;
+
+       case UART_MCR:
+               mdev_state->s[index].uart_reg[offset] = data;
+
+               if ((mdev_state->s[index].uart_reg[UART_IER] & UART_IER_MSI) &&
+                               (data & UART_MCR_OUT2)) {
+#if defined(DEBUG_INTR)
+                       pr_err("Serial port %d: MCR_OUT2 write\n", index);
+#endif
+                       mtty_trigger_interrupt(mdev_state->mdev->uuid);
+               }
+
+               if ((mdev_state->s[index].uart_reg[UART_IER] & UART_IER_MSI) &&
+                               (data & (UART_MCR_RTS | UART_MCR_DTR))) {
+#if defined(DEBUG_INTR)
+                       pr_err("Serial port %d: MCR RTS/DTR write\n", index);
+#endif
+                       mtty_trigger_interrupt(mdev_state->mdev->uuid);
+               }
+               break;
+
+       case UART_LSR:
+       case UART_MSR:
+               /* do nothing */
+               break;
+
+       case UART_SCR:
+               mdev_state->s[index].uart_reg[offset] = data;
+               break;
+
+       default:
+               break;
+       }
+}
+
+static void handle_bar_read(unsigned int index, struct mdev_state *mdev_state,
+                           u16 offset, char *buf, u32 count)
+{
+       /* Handle read requests by guest */
+       switch (offset) {
+       case UART_RX:
+               /* if DLAB set, data is LSB of divisor */
+               if (mdev_state->s[index].dlab) {
+                       *buf  = (u8)mdev_state->s[index].divisor;
+                       break;
+               }
+
+               mutex_lock(&mdev_state->rxtx_lock);
+               /* return data in tx buffer */
+               if (mdev_state->s[index].rxtx.head !=
+                                mdev_state->s[index].rxtx.tail) {
+                       *buf = mdev_state->s[index].rxtx.fifo[
+                                               mdev_state->s[index].rxtx.tail];
+                       mdev_state->s[index].rxtx.count--;
+                       CIRCULAR_BUF_INC_IDX(mdev_state->s[index].rxtx.tail);
+               }
+
+               if (mdev_state->s[index].rxtx.head ==
+                               mdev_state->s[index].rxtx.tail) {
+               /*
+                *  Trigger interrupt if tx buffer empty interrupt is
+                *  enabled and fifo is empty
+                */
+#if defined(DEBUG_INTR)
+                       pr_err("Serial port %d: Buffer Empty\n", index);
+#endif
+                       if (mdev_state->s[index].uart_reg[UART_IER] &
+                                                        UART_IER_THRI)
+                               mtty_trigger_interrupt(mdev_state->mdev->uuid);
+               }
+               mutex_unlock(&mdev_state->rxtx_lock);
+
+               break;
+
+       case UART_IER:
+               if (mdev_state->s[index].dlab) {
+                       *buf = (u8)(mdev_state->s[index].divisor >> 8);
+                       break;
+               }
+               *buf = mdev_state->s[index].uart_reg[offset] & 0x0f;
+               break;
+
+       case UART_IIR:
+       {
+               u8 ier = mdev_state->s[index].uart_reg[UART_IER];
+               *buf = 0;
+
+               mutex_lock(&mdev_state->rxtx_lock);
+               /* Interrupt priority 1: Parity, overrun, framing or break */
+               if ((ier & UART_IER_RLSI) && mdev_state->s[index].overrun)
+                       *buf |= UART_IIR_RLSI;
+
+               /* Interrupt priority 2: Fifo trigger level reached */
+               if ((ier & UART_IER_RDI) &&
+                   (mdev_state->s[index].rxtx.count ==
+                     mdev_state->s[index].intr_trigger_level))
+                       *buf |= UART_IIR_RDI;
+
+               /* Interrupt priotiry 3: transmitter holding register empty */
+               if ((ier & UART_IER_THRI) &&
+                   (mdev_state->s[index].rxtx.head ==
+                               mdev_state->s[index].rxtx.tail))
+                       *buf |= UART_IIR_THRI;
+
+               /* Interrupt priotiry 4: Modem status: CTS, DSR, RI or DCD  */
+               if ((ier & UART_IER_MSI) &&
+                   (mdev_state->s[index].uart_reg[UART_MCR] &
+                                (UART_MCR_RTS | UART_MCR_DTR)))
+                       *buf |= UART_IIR_MSI;
+
+               /* bit0: 0=> interrupt pending, 1=> no interrupt is pending */
+               if (*buf == 0)
+                       *buf = UART_IIR_NO_INT;
+
+               /* set bit 6 & 7 to be 16550 compatible */
+               *buf |= 0xC0;
+               mutex_unlock(&mdev_state->rxtx_lock);
+       }
+       break;
+
+       case UART_LCR:
+       case UART_MCR:
+               *buf = mdev_state->s[index].uart_reg[offset];
+               break;
+
+       case UART_LSR:
+       {
+               u8 lsr = 0;
+
+               mutex_lock(&mdev_state->rxtx_lock);
+               /* atleast one char in FIFO */
+               if (mdev_state->s[index].rxtx.head !=
+                                mdev_state->s[index].rxtx.tail)
+                       lsr |= UART_LSR_DR;
+
+               /* if FIFO overrun */
+               if (mdev_state->s[index].overrun)
+                       lsr |= UART_LSR_OE;
+
+               /* transmit FIFO empty and tramsitter empty */
+               if (mdev_state->s[index].rxtx.head ==
+                                mdev_state->s[index].rxtx.tail)
+                       lsr |= UART_LSR_TEMT | UART_LSR_THRE;
+
+               mutex_unlock(&mdev_state->rxtx_lock);
+               *buf = lsr;
+               break;
+       }
+       case UART_MSR:
+               *buf = UART_MSR_DSR | UART_MSR_DDSR | UART_MSR_DCD;
+
+               mutex_lock(&mdev_state->rxtx_lock);
+               /* if AFE is 1 and FIFO have space, set CTS bit */
+               if (mdev_state->s[index].uart_reg[UART_MCR] &
+                                                UART_MCR_AFE) {
+                       if (mdev_state->s[index].rxtx.count <
+                                       mdev_state->s[index].max_fifo_size)
+                               *buf |= UART_MSR_CTS | UART_MSR_DCTS;
+               } else
+                       *buf |= UART_MSR_CTS | UART_MSR_DCTS;
+               mutex_unlock(&mdev_state->rxtx_lock);
+
+               break;
+
+       case UART_SCR:
+               *buf = mdev_state->s[index].uart_reg[offset];
+               break;
+
+       default:
+               break;
+       }
+}
+
+static void mdev_read_base(struct mdev_state *mdev_state)
+{
+       int index, pos;
+       u32 start_lo, start_hi;
+       u32 mem_type;
+
+       pos = PCI_BASE_ADDRESS_0;
+
+       for (index = 0; index <= VFIO_PCI_BAR5_REGION_INDEX; index++) {
+
+               if (!mdev_state->region_info[index].size)
+                       continue;
+
+               start_lo = (*(u32 *)(mdev_state->vconfig + pos)) &
+                       PCI_BASE_ADDRESS_MEM_MASK;
+               mem_type = (*(u32 *)(mdev_state->vconfig + pos)) &
+                       PCI_BASE_ADDRESS_MEM_TYPE_MASK;
+
+               switch (mem_type) {
+               case PCI_BASE_ADDRESS_MEM_TYPE_64:
+                       start_hi = (*(u32 *)(mdev_state->vconfig + pos + 4));
+                       pos += 4;
+                       break;
+               case PCI_BASE_ADDRESS_MEM_TYPE_32:
+               case PCI_BASE_ADDRESS_MEM_TYPE_1M:
+                       /* 1M mem BAR treated as 32-bit BAR */
+               default:
+                       /* mem unknown type treated as 32-bit BAR */
+                       start_hi = 0;
+                       break;
+               }
+               pos += 4;
+               mdev_state->region_info[index].start = ((u64)start_hi << 32) |
+                                                       start_lo;
+       }
+}
+
+static ssize_t mdev_access(struct mdev_device *mdev, char *buf,
+               size_t count, loff_t pos, bool is_write)
+{
+       struct mdev_state *mdev_state;
+       unsigned int index;
+       loff_t offset;
+       int ret = 0;
+
+       if (!mdev || !buf)
+               return -EINVAL;
+
+       mdev_state = mdev_get_drvdata(mdev);
+       if (!mdev_state) {
+               pr_err("%s mdev_state not found\n", __func__);
+               return -EINVAL;
+       }
+
+       mutex_lock(&mdev_state->ops_lock);
+
+       index = MTTY_VFIO_PCI_OFFSET_TO_INDEX(pos);
+       offset = pos & MTTY_VFIO_PCI_OFFSET_MASK;
+       switch (index) {
+       case VFIO_PCI_CONFIG_REGION_INDEX:
+
+#if defined(DEBUG)
+               pr_info("%s: PCI config space %s at offset 0x%llx\n",
+                        __func__, is_write ? "write" : "read", offset);
+#endif
+               if (is_write) {
+                       dump_buffer(buf, count);
+                       handle_pci_cfg_write(mdev_state, offset, buf, count);
+               } else {
+                       memcpy(buf, (mdev_state->vconfig + offset), count);
+                       dump_buffer(buf, count);
+               }
+
+               break;
+
+       case VFIO_PCI_BAR0_REGION_INDEX ... VFIO_PCI_BAR5_REGION_INDEX:
+               if (!mdev_state->region_info[index].start)
+                       mdev_read_base(mdev_state);
+
+               if (is_write) {
+                       dump_buffer(buf, count);
+
+#if defined(DEBUG_REGS)
+                       pr_info("%s: BAR%d  WR @0x%llx %s val:0x%02x dlab:%d\n",
+                               __func__, index, offset, wr_reg[offset],
+                               (u8)*buf, mdev_state->s[index].dlab);
+#endif
+                       handle_bar_write(index, mdev_state, offset, buf, count);
+               } else {
+                       handle_bar_read(index, mdev_state, offset, buf, count);
+                       dump_buffer(buf, count);
+
+#if defined(DEBUG_REGS)
+                       pr_info("%s: BAR%d  RD @0x%llx %s val:0x%02x dlab:%d\n",
+                               __func__, index, offset, rd_reg[offset],
+                               (u8)*buf, mdev_state->s[index].dlab);
+#endif
+               }
+               break;
+
+       default:
+               ret = -1;
+               goto accessfailed;
+       }
+
+       ret = count;
+
+
+accessfailed:
+       mutex_unlock(&mdev_state->ops_lock);
+
+       return ret;
+}
+
+int mtty_create(struct kobject *kobj, struct mdev_device *mdev)
+{
+       struct mdev_state *mdev_state;
+       char name[MTTY_STRING_LEN];
+       int nr_ports = 0, i;
+
+       if (!mdev)
+               return -EINVAL;
+
+       for (i = 0; i < 2; i++) {
+               snprintf(name, MTTY_STRING_LEN, "%s-%d",
+                       dev_driver_string(mdev->parent->dev), i + 1);
+               if (!strcmp(kobj->name, name)) {
+                       nr_ports = i + 1;
+                       break;
+               }
+       }
+
+       if (!nr_ports)
+               return -EINVAL;
+
+       mdev_state = kzalloc(sizeof(struct mdev_state), GFP_KERNEL);
+       if (mdev_state == NULL)
+               return -ENOMEM;
+
+       mdev_state->nr_ports = nr_ports;
+       mdev_state->irq_index = -1;
+       mdev_state->s[0].max_fifo_size = MAX_FIFO_SIZE;
+       mdev_state->s[1].max_fifo_size = MAX_FIFO_SIZE;
+       mutex_init(&mdev_state->rxtx_lock);
+       mdev_state->vconfig = kzalloc(MTTY_CONFIG_SPACE_SIZE, GFP_KERNEL);
+
+       if (mdev_state->vconfig == NULL) {
+               kfree(mdev_state);
+               return -ENOMEM;
+       }
+
+       mutex_init(&mdev_state->ops_lock);
+       mdev_state->mdev = mdev;
+       mdev_set_drvdata(mdev, mdev_state);
+
+       mtty_create_config_space(mdev_state);
+
+       mutex_lock(&mdev_list_lock);
+       list_add(&mdev_state->next, &mdev_devices_list);
+       mutex_unlock(&mdev_list_lock);
+
+       return 0;
+}
+
+int mtty_remove(struct mdev_device *mdev)
+{
+       struct mdev_state *mds, *tmp_mds;
+       struct mdev_state *mdev_state = mdev_get_drvdata(mdev);
+       int ret = -EINVAL;
+
+       mutex_lock(&mdev_list_lock);
+       list_for_each_entry_safe(mds, tmp_mds, &mdev_devices_list, next) {
+               if (mdev_state == mds) {
+                       list_del(&mdev_state->next);
+                       mdev_set_drvdata(mdev, NULL);
+                       kfree(mdev_state->vconfig);
+                       kfree(mdev_state);
+                       ret = 0;
+                       break;
+               }
+       }
+       mutex_unlock(&mdev_list_lock);
+
+       return ret;
+}
+
+int mtty_reset(struct mdev_device *mdev)
+{
+       struct mdev_state *mdev_state;
+
+       if (!mdev)
+               return -EINVAL;
+
+       mdev_state = mdev_get_drvdata(mdev);
+       if (!mdev_state)
+               return -EINVAL;
+
+       pr_info("%s: called\n", __func__);
+
+       return 0;
+}
+
+ssize_t mtty_read(struct mdev_device *mdev, char __user *buf,
+                       size_t count, loff_t *ppos)
+{
+       return mdev_access(mdev, buf, count, *ppos, false);
+}
+
+ssize_t mtty_write(struct mdev_device *mdev, const char __user *buf,
+                        size_t count, loff_t *ppos)
+{
+       return mdev_access(mdev, (char *)buf, count, *ppos, true);
+}
+
+static int mtty_set_irqs(struct mdev_device *mdev, uint32_t flags,
+                        unsigned int index, unsigned int start,
+                        unsigned int count, void *data)
+{
+       int ret = 0;
+       struct mdev_state *mdev_state;
+
+       if (!mdev)
+               return -EINVAL;
+
+       mdev_state = mdev_get_drvdata(mdev);
+       if (!mdev_state)
+               return -EINVAL;
+
+       mutex_lock(&mdev_state->ops_lock);
+       switch (index) {
+       case VFIO_PCI_INTX_IRQ_INDEX:
+               switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
+               case VFIO_IRQ_SET_ACTION_MASK:
+               case VFIO_IRQ_SET_ACTION_UNMASK:
+                       break;
+               case VFIO_IRQ_SET_ACTION_TRIGGER:
+               {
+                       if (flags & VFIO_IRQ_SET_DATA_NONE) {
+                               pr_info("%s: disable INTx\n", __func__);
+                               break;
+                       }
+
+                       if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
+                               int fd = *(int *)data;
+
+                               if (fd > 0) {
+                                       struct fd irqfd;
+
+                                       irqfd = fdget(fd);
+                                       if (!irqfd.file) {
+                                               ret = -EBADF;
+                                               break;
+                                       }
+                                       mdev_state->intx_file = irqfd.file;
+                                       fdput(irqfd);
+                                       mdev_state->irq_fd = fd;
+                                       mdev_state->irq_index = index;
+                                       break;
+                               }
+                       }
+                       break;
+               }
+               }
+               break;
+       case VFIO_PCI_MSI_IRQ_INDEX:
+               switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
+               case VFIO_IRQ_SET_ACTION_MASK:
+               case VFIO_IRQ_SET_ACTION_UNMASK:
+                       break;
+               case VFIO_IRQ_SET_ACTION_TRIGGER:
+                       if (flags & VFIO_IRQ_SET_DATA_NONE) {
+                               pr_info("%s: disable MSI\n", __func__);
+                               mdev_state->irq_index = VFIO_PCI_INTX_IRQ_INDEX;
+                               break;
+                       }
+                       if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
+                               int fd = *(int *)data;
+                               struct fd irqfd;
+
+                               if (fd <= 0)
+                                       break;
+
+                               if (mdev_state->msi_file)
+                                       break;
+
+                               irqfd = fdget(fd);
+                               if (!irqfd.file) {
+                                       ret = -EBADF;
+                                       break;
+                               }
+
+                               mdev_state->msi_file = irqfd.file;
+                               fdput(irqfd);
+                               mdev_state->irq_fd = fd;
+                               mdev_state->irq_index = index;
+                       }
+                       break;
+       }
+       break;
+       case VFIO_PCI_MSIX_IRQ_INDEX:
+               pr_info("%s: MSIX_IRQ\n", __func__);
+               break;
+       case VFIO_PCI_ERR_IRQ_INDEX:
+               pr_info("%s: ERR_IRQ\n", __func__);
+               break;
+       case VFIO_PCI_REQ_IRQ_INDEX:
+               pr_info("%s: REQ_IRQ\n", __func__);
+               break;
+       }
+
+       mutex_unlock(&mdev_state->ops_lock);
+       return ret;
+}
+
+static int mtty_trigger_interrupt(uuid_le uuid)
+{
+       mm_segment_t old_fs;
+       u64 val = 1;
+       loff_t offset = 0;
+       int ret = -1;
+       struct file *pfile = NULL;
+       struct mdev_state *mdev_state;
+
+       mdev_state = find_mdev_state_by_uuid(uuid);
+
+       if (!mdev_state) {
+               pr_info("%s: mdev not found\n", __func__);
+               return -EINVAL;
+       }
+
+       if ((mdev_state->irq_index == VFIO_PCI_MSI_IRQ_INDEX) &&
+                       (mdev_state->msi_file == NULL))
+               return -EINVAL;
+       else if ((mdev_state->irq_index == VFIO_PCI_INTX_IRQ_INDEX) &&
+                       (mdev_state->intx_file == NULL)) {
+               pr_info("%s: Intr file not found\n", __func__);
+               return -EINVAL;
+       }
+
+       old_fs = get_fs();
+       set_fs(KERNEL_DS);
+
+       if (mdev_state->irq_index == VFIO_PCI_MSI_IRQ_INDEX)
+               pfile = mdev_state->msi_file;
+       else
+               pfile = mdev_state->intx_file;
+
+       if (pfile && pfile->f_op && pfile->f_op->write) {
+               ret = pfile->f_op->write(pfile, (char *)&val, sizeof(val),
+                                        &offset);
+#if defined(DEBUG_INTR)
+               pr_info("Intx triggered\n");
+#endif
+       } else
+               pr_err("%s: pfile not valid, intr_type = %d\n", __func__,
+                               mdev_state->irq_index);
+
+       set_fs(old_fs);
+
+       if (ret < 0)
+               pr_err("%s: eventfd write failed (%d)\n", __func__, ret);
+
+       return ret;
+}
+
+int mtty_get_region_info(struct mdev_device *mdev,
+                        struct vfio_region_info *region_info,
+                        u16 *cap_type_id, void **cap_type)
+{
+       unsigned int size = 0;
+       struct mdev_state *mdev_state;
+       int bar_index;
+
+       if (!mdev)
+               return -EINVAL;
+
+       mdev_state = mdev_get_drvdata(mdev);
+       if (!mdev_state)
+               return -EINVAL;
+
+       mutex_lock(&mdev_state->ops_lock);
+       bar_index = region_info->index;
+
+       switch (bar_index) {
+       case VFIO_PCI_CONFIG_REGION_INDEX:
+               size = MTTY_CONFIG_SPACE_SIZE;
+               break;
+       case VFIO_PCI_BAR0_REGION_INDEX:
+               size = MTTY_IO_BAR_SIZE;
+               break;
+       case VFIO_PCI_BAR1_REGION_INDEX:
+               if (mdev_state->nr_ports == 2)
+                       size = MTTY_IO_BAR_SIZE;
+               break;
+       default:
+               size = 0;
+               break;
+       }
+
+       mdev_state->region_info[bar_index].size = size;
+       mdev_state->region_info[bar_index].vfio_offset =
+               MTTY_VFIO_PCI_INDEX_TO_OFFSET(bar_index);
+
+       region_info->size = size;
+       region_info->offset = MTTY_VFIO_PCI_INDEX_TO_OFFSET(bar_index);
+       region_info->flags = VFIO_REGION_INFO_FLAG_READ |
+               VFIO_REGION_INFO_FLAG_WRITE;
+       mutex_unlock(&mdev_state->ops_lock);
+       return 0;
+}
+
+int mtty_get_irq_info(struct mdev_device *mdev, struct vfio_irq_info *irq_info)
+{
+       switch (irq_info->index) {
+       case VFIO_PCI_INTX_IRQ_INDEX:
+       case VFIO_PCI_MSI_IRQ_INDEX:
+       case VFIO_PCI_REQ_IRQ_INDEX:
+               break;
+
+       default:
+               return -EINVAL;
+       }
+
+       irq_info->flags = VFIO_IRQ_INFO_EVENTFD;
+       irq_info->count = 1;
+
+       if (irq_info->index == VFIO_PCI_INTX_IRQ_INDEX)
+               irq_info->flags |= (VFIO_IRQ_INFO_MASKABLE |
+                               VFIO_IRQ_INFO_AUTOMASKED);
+       else
+               irq_info->flags |= VFIO_IRQ_INFO_NORESIZE;
+
+       return 0;
+}
+
+int mtty_get_device_info(struct mdev_device *mdev,
+                        struct vfio_device_info *dev_info)
+{
+       dev_info->flags = VFIO_DEVICE_FLAGS_PCI;
+       dev_info->num_regions = VFIO_PCI_NUM_REGIONS;
+       dev_info->num_irqs = VFIO_PCI_NUM_IRQS;
+
+       return 0;
+}
+
+static long mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
+                       unsigned long arg)
+{
+       int ret = 0;
+       unsigned long minsz;
+       struct mdev_state *mdev_state;
+
+       if (!mdev)
+               return -EINVAL;
+
+       mdev_state = mdev_get_drvdata(mdev);
+       if (!mdev_state)
+               return -ENODEV;
+
+       switch (cmd) {
+       case VFIO_DEVICE_GET_INFO:
+       {
+               struct vfio_device_info info;
+
+               minsz = offsetofend(struct vfio_device_info, num_irqs);
+
+               if (copy_from_user(&info, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               if (info.argsz < minsz)
+                       return -EINVAL;
+
+               ret = mtty_get_device_info(mdev, &info);
+               if (ret)
+                       return ret;
+
+               memcpy(&mdev_state->dev_info, &info, sizeof(info));
+
+               return copy_to_user((void __user *)arg, &info, minsz);
+       }
+       case VFIO_DEVICE_GET_REGION_INFO:
+       {
+               struct vfio_region_info info;
+               struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
+               u16 cap_type_id = 0;
+               void *cap_type = NULL;
+
+               minsz = offsetofend(struct vfio_region_info, offset);
+
+               if (copy_from_user(&info, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               if (info.argsz < minsz)
+                       return -EINVAL;
+
+               ret = mtty_get_region_info(mdev, &info, &cap_type_id,
+                                          &cap_type);
+               if (ret)
+                       return ret;
+
+               ret = vfio_info_add_capability(&info, &caps, cap_type_id,
+                                               cap_type);
+               if (ret)
+                       return ret;
+
+               if (info.cap_offset) {
+                       if (copy_to_user((void __user *)arg + info.cap_offset,
+                                               caps.buf, caps.size)) {
+                               kfree(caps.buf);
+                               return -EFAULT;
+                       }
+                       kfree(caps.buf);
+               }
+
+               return copy_to_user((void __user *)arg, &info, minsz);
+       }
+
+       case VFIO_DEVICE_GET_IRQ_INFO:
+       {
+               struct vfio_irq_info info;
+
+               minsz = offsetofend(struct vfio_irq_info, count);
+
+               if (copy_from_user(&info, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               if ((info.argsz < minsz) ||
+                   (info.index >= mdev_state->dev_info.num_irqs))
+                       return -EINVAL;
+
+               ret = mtty_get_irq_info(mdev, &info);
+               if (ret)
+                       return ret;
+
+               if (info.count == -1)
+                       return -EINVAL;
+
+               return copy_to_user((void __user *)arg, &info, minsz);
+       }
+       case VFIO_DEVICE_SET_IRQS:
+       {
+               struct vfio_irq_set hdr;
+               u8 *data = NULL, *ptr = NULL;
+               size_t data_size = 0;
+
+               minsz = offsetofend(struct vfio_irq_set, count);
+
+               if (copy_from_user(&hdr, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               ret = vfio_set_irqs_validate_and_prepare(&hdr,
+                               mdev_state->dev_info.num_irqs,
+                               VFIO_PCI_NUM_IRQS,
+                               &data_size);
+               if (ret)
+                       return ret;
+
+               if (data_size) {
+                       ptr = data = memdup_user((void __user *)(arg + minsz),
+                                       data_size);
+                       if (IS_ERR(data))
+                               return PTR_ERR(data);
+               }
+
+               ret = mtty_set_irqs(mdev, hdr.flags, hdr.index, hdr.start,
+                               hdr.count, data);
+
+               kfree(ptr);
+               return ret;
+       }
+       case VFIO_DEVICE_RESET:
+               return mtty_reset(mdev);
+       }
+       return -ENOTTY;
+}
+
+int mtty_open(struct mdev_device *mdev)
+{
+       pr_info("%s\n", __func__);
+       return 0;
+}
+
+void mtty_close(struct mdev_device *mdev)
+{
+       pr_info("%s\n", __func__);
+}
+
+static ssize_t
+sample_mtty_dev_show(struct device *dev, struct device_attribute *attr,
+                    char *buf)
+{
+       return sprintf(buf, "This is phy device\n");
+}
+
+static DEVICE_ATTR_RO(sample_mtty_dev);
+
+static struct attribute *mtty_dev_attrs[] = {
+       &dev_attr_sample_mtty_dev.attr,
+       NULL,
+};
+
+static const struct attribute_group mtty_dev_group = {
+       .name  = "mtty_dev",
+       .attrs = mtty_dev_attrs,
+};
+
+const struct attribute_group *mtty_dev_groups[] = {
+       &mtty_dev_group,
+       NULL,
+};
+
+static ssize_t
+sample_mdev_dev_show(struct device *dev, struct device_attribute *attr,
+                    char *buf)
+{
+       struct mdev_device *mdev = to_mdev_device(dev);
+
+       if (mdev)
+               return sprintf(buf, "This is MDEV %s\n", dev_name(&mdev->dev));
+
+       return sprintf(buf, "\n");
+}
+
+static DEVICE_ATTR_RO(sample_mdev_dev);
+
+static struct attribute *mdev_dev_attrs[] = {
+       &dev_attr_sample_mdev_dev.attr,
+       NULL,
+};
+
+static const struct attribute_group mdev_dev_group = {
+       .name  = "vendor",
+       .attrs = mdev_dev_attrs,
+};
+
+const struct attribute_group *mdev_dev_groups[] = {
+       &mdev_dev_group,
+       NULL,
+};
+
+static ssize_t
+name_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+       char name[MTTY_STRING_LEN];
+       int i;
+       const char *name_str[2] = {"Single port serial", "Dual port serial"};
+
+       for (i = 0; i < 2; i++) {
+               snprintf(name, MTTY_STRING_LEN, "%s-%d",
+                        dev_driver_string(dev), i + 1);
+               if (!strcmp(kobj->name, name))
+                       return sprintf(buf, "%s\n", name_str[i]);
+       }
+
+       return -EINVAL;
+}
+
+MDEV_TYPE_ATTR_RO(name);
+
+static ssize_t
+available_instances_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+       char name[MTTY_STRING_LEN];
+       int i;
+       struct mdev_state *mds;
+       int ports = 0, used = 0;
+
+       for (i = 0; i < 2; i++) {
+               snprintf(name, MTTY_STRING_LEN, "%s-%d",
+                        dev_driver_string(dev), i + 1);
+               if (!strcmp(kobj->name, name)) {
+                       ports = i + 1;
+                       break;
+               }
+       }
+
+       if (!ports)
+               return -EINVAL;
+
+       list_for_each_entry(mds, &mdev_devices_list, next)
+               used += mds->nr_ports;
+
+       return sprintf(buf, "%d\n", (MAX_MTTYS - used)/ports);
+}
+
+MDEV_TYPE_ATTR_RO(available_instances);
+
+
+static ssize_t device_api_show(struct kobject *kobj, struct device *dev,
+                              char *buf)
+{
+       return sprintf(buf, "%s\n",
+                      vfio_device_api_string(VFIO_DEVICE_FLAGS_PCI));
+}
+
+MDEV_TYPE_ATTR_RO(device_api);
+
+static struct attribute *mdev_types_attrs[] = {
+       &mdev_type_attr_name.attr,
+       &mdev_type_attr_device_api.attr,
+       &mdev_type_attr_available_instances.attr,
+       NULL,
+};
+
+static struct attribute_group mdev_type_group1 = {
+       .name  = "1",
+       .attrs = mdev_types_attrs,
+};
+
+static struct attribute_group mdev_type_group2 = {
+       .name  = "2",
+       .attrs = mdev_types_attrs,
+};
+
+struct attribute_group *mdev_type_groups[] = {
+       &mdev_type_group1,
+       &mdev_type_group2,
+       NULL,
+};
+
+struct parent_ops mdev_fops = {
+       .owner                  = THIS_MODULE,
+       .dev_attr_groups        = mtty_dev_groups,
+       .mdev_attr_groups       = mdev_dev_groups,
+       .supported_type_groups  = mdev_type_groups,
+       .create                 = mtty_create,
+       .remove                 = mtty_remove,
+       .open                   = mtty_open,
+       .release                = mtty_close,
+       .read                   = mtty_read,
+       .write                  = mtty_write,
+       .ioctl                  = mtty_ioctl,
+};
+
+static void mtty_device_release(struct device *dev)
+{
+       dev_dbg(dev, "mtty: released\n");
+}
+
+static int __init mtty_dev_init(void)
+{
+       int ret = 0;
+
+       pr_info("mtty_dev: %s\n", __func__);
+
+       memset(&mtty_dev, 0, sizeof(mtty_dev));
+
+       idr_init(&mtty_dev.vd_idr);
+
+       ret = alloc_chrdev_region(&mtty_dev.vd_devt, 0, MINORMASK, MTTY_NAME);
+
+       if (ret < 0) {
+               pr_err("Error: failed to register mtty_dev, err:%d\n", ret);
+               return ret;
+       }
+
+       cdev_init(&mtty_dev.vd_cdev, &vd_fops);
+       cdev_add(&mtty_dev.vd_cdev, mtty_dev.vd_devt, MINORMASK);
+
+       pr_info("major_number:%d\n", MAJOR(mtty_dev.vd_devt));
+
+       mtty_dev.vd_class = class_create(THIS_MODULE, MTTY_CLASS_NAME);
+
+       if (IS_ERR(mtty_dev.vd_class)) {
+               pr_err("Error: failed to register mtty_dev class\n");
+               goto failed1;
+       }
+
+       mtty_dev.dev.class = mtty_dev.vd_class;
+       mtty_dev.dev.release = mtty_device_release;
+       dev_set_name(&mtty_dev.dev, "%s", MTTY_NAME);
+
+       ret = device_register(&mtty_dev.dev);
+       if (ret)
+               goto failed2;
+
+       if (mdev_register_device(&mtty_dev.dev, &mdev_fops) != 0)
+               goto failed3;
+
+       mutex_init(&mdev_list_lock);
+       INIT_LIST_HEAD(&mdev_devices_list);
+
+       goto all_done;
+
+failed3:
+
+       device_unregister(&mtty_dev.dev);
+failed2:
+       class_destroy(mtty_dev.vd_class);
+
+failed1:
+       cdev_del(&mtty_dev.vd_cdev);
+       unregister_chrdev_region(mtty_dev.vd_devt, MINORMASK);
+
+all_done:
+       return ret;
+}
+
+static void __exit mtty_dev_exit(void)
+{
+       mtty_dev.dev.bus = NULL;
+       mdev_unregister_device(&mtty_dev.dev);
+
+       device_unregister(&mtty_dev.dev);
+       idr_destroy(&mtty_dev.vd_idr);
+       cdev_del(&mtty_dev.vd_cdev);
+       unregister_chrdev_region(mtty_dev.vd_devt, MINORMASK);
+       class_destroy(mtty_dev.vd_class);
+       mtty_dev.vd_class = NULL;
+       pr_info("mtty_dev: Unloaded!\n");
+}
+
+module_init(mtty_dev_init)
+module_exit(mtty_dev_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_INFO(supported, "Test driver that simulate serial port over PCI");
+MODULE_VERSION(VERSION_STRING);
+MODULE_AUTHOR(DRIVER_AUTHOR);
diff --git a/Documentation/vfio-mdev/vfio-mediated-device.txt 
b/Documentation/vfio-mdev/vfio-mediated-device.txt
index 8746e88dca4d..1b99db97a6eb 100644
--- a/Documentation/vfio-mdev/vfio-mediated-device.txt
+++ b/Documentation/vfio-mdev/vfio-mediated-device.txt
@@ -279,11 +279,111 @@ these callbacks are supported in the TYPE1 IOMMU module. 
To enable them for
 other IOMMU backend modules, such as PPC64 sPAPR module, they need to provide
 these two callback functions.
 
+Using the Sample Code
+=====================
+
+mtty.c in this folder is a sample driver program to demonstrate how to use the
+mediated device framework.
+
+The sample driver creates an mdev device that simulates a serial port over a 
PCI
+card.
+
+1. Build and load the mtty.ko module.
+
+   This step creates a dummy device, /sys/devices/virtual/mtty/mtty/
+
+   Files in this device directory in sysfs are similar to the following:
+
+   # tree /sys/devices/virtual/mtty/mtty/
+      /sys/devices/virtual/mtty/mtty/
+      |-- mdev_supported_types
+      |   |-- mtty-1
+      |   |   |-- available_instances
+      |   |   |-- create
+      |   |   |-- device_api
+      |   |   |-- devices
+      |   |   `-- name
+      |   `-- mtty-2
+      |       |-- available_instances
+      |       |-- create
+      |       |-- device_api
+      |       |-- devices
+      |       `-- name
+      |-- mtty_dev
+      |   `-- sample_mtty_dev
+      |-- power
+      |   |-- autosuspend_delay_ms
+      |   |-- control
+      |   |-- runtime_active_time
+      |   |-- runtime_status
+      |   `-- runtime_suspended_time
+      |-- subsystem -> ../../../../class/mtty
+      `-- uevent
+
+2. Create a mediated device by using the dummy device that you created in the
+   previous step.
+
+   # echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001" >     \
+              /sys/devices/virtual/mtty/mtty/mdev_supported_types/mtty-2/create
+
+3. Add parameters to qemu-kvm.
+
+   -device vfio-pci,\
+    sysfsdev=/sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001
+
+4. Boot the VM.
+
+   In the Linux guest VM, with no hardware on the host, the device appears
+   as  follows:
+
+   # lspci -s 00:05.0 -xxvv
+   00:05.0 Serial controller: Device 4348:3253 (rev 10) (prog-if 02 [16550])
+           Subsystem: Device 4348:3253
+           Physical Slot: 5
+           Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-
+   Stepping- SERR- FastB2B- DisINTx-
+           Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort-
+   <TAbort- <MAbort- >SERR- <PERR- INTx-
+           Interrupt: pin A routed to IRQ 10
+           Region 0: I/O ports at c150 [size=8]
+           Region 1: I/O ports at c158 [size=8]
+           Kernel driver in use: serial
+   00: 48 43 53 32 01 00 00 02 10 02 00 07 00 00 00 00
+   10: 51 c1 00 00 59 c1 00 00 00 00 00 00 00 00 00 00
+   20: 00 00 00 00 00 00 00 00 00 00 00 00 48 43 53 32
+   30: 00 00 00 00 00 00 00 00 00 00 00 00 0a 01 00 00
+
+   In the Linux guest VM, dmesg output for the device is as follows:
+
+   serial 0000:00:05.0: PCI INT A -> Link[LNKA] -> GSI 10 (level, high) -> IRQ
+10
+   0000:00:05.0: ttyS1 at I/O 0xc150 (irq = 10) is a 16550A
+   0000:00:05.0: ttyS2 at I/O 0xc158 (irq = 10) is a 16550A
+
+
+5. In the Linux guest VM, check the serial ports.
+
+   # setserial -g /dev/ttyS*
+   /dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
+   /dev/ttyS1, UART: 16550A, Port: 0xc150, IRQ: 10
+   /dev/ttyS2, UART: 16550A, Port: 0xc158, IRQ: 10
+
+6. Using a minicom or any terminal enulation program, open port /dev/ttyS1 or
+   /dev/ttyS2 with hardware flow control disabled.
+
+7. Type data on the minicom terminal or send data to the terminal emulation
+   program and read the data.
+
+   Data is loop backed from hosts mtty driver.
+
+8. Destroy the mediated device that you created.
+
+   # echo 1 > /sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001/remove
+
 References
-----------
+==========
 
 [1] See Documentation/vfio.txt for more information on VFIO.
 [2] struct mdev_driver in include/linux/mdev.h
 [3] struct parent_ops in include/linux/mdev.h
 [4] struct vfio_iommu_driver_ops in include/linux/vfio.h
-
-- 
2.7.0

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