/*
 * g_serial.c -- USB gadget serial driver
 *
 * Copyright 2003 (C) Al Borchers (alborchers@steinerpoint.com)
 *
 * This code is based in part on the Gadget Zero driver, which
 * is Copyright (C) 2003 by David Brownell, all rights reserved.
 *
 * This code also borrows from usbserial.c, which is
 * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
 * Copyright (C) 2000 Peter Berger (pberger@brimson.com)
 * Copyright (C) 2000 Al Borchers (alborchers@steinerpoint.com)
 *
 * This software is distributed under the terms of the GNU General
 * Public License ("GPL") as published by the Free Software Foundation,
 * either version 2 of that License or (at your option) any later version.
 *
 */

#include <linux/kernel.h>
#include <linux/utsname.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>

#include <linux/usb/ch9.h>
#include <linux/usb/cdc.h>
#include <linux/usb/gadget.h>

#include "gadget_chips.h"


/* Defines */

#define GS_VERSION_STR                  "v2.2"
#define GS_VERSION_NUM                  0x0202

#define GS_LONG_NAME                    "Gadget Serial"
#define GS_SHORT_NAME                   "g_serial"

#define GS_MAJOR                        127
#define GS_MINOR_START                  0

#define GS_NUM_PORTS                    16

#define GS_NUM_CONFIGS                  1
#define GS_NO_CONFIG_ID                 0
#define GS_BULK_CONFIG_ID               1
#define GS_ACM_CONFIG_ID                2

#define GS_MAX_NUM_INTERFACES           2
#define GS_BULK_INTERFACE_ID            0
#define GS_CONTROL_INTERFACE_ID         0
#define GS_DATA_INTERFACE_ID            1

#define GS_MAX_DESC_LEN                 256

#define GS_DEFAULT_READ_Q_SIZE          32
#define GS_DEFAULT_WRITE_Q_SIZE         32

#define GS_DEFAULT_WRITE_BUF_SIZE       8192
#define GS_TMP_BUF_SIZE                 8192

#define GS_CLOSE_TIMEOUT                15

#define GS_DEFAULT_USE_ACM              0

#define GS_DEFAULT_DTE_RATE             9600
#define GS_DEFAULT_DATA_BITS            8
#define GS_DEFAULT_PARITY               USB_CDC_NO_PARITY
#define GS_DEFAULT_CHAR_FORMAT          USB_CDC_1_STOP_BITS

/* maxpacket and other transfer characteristics vary by speed. */
static inline struct usb_endpoint_descriptor *
choose_ep_desc(struct usb_gadget *g, struct usb_endpoint_descriptor *hs,
                struct usb_endpoint_descriptor *fs)
{
        if (gadget_is_dualspeed(g) && g->speed == USB_SPEED_HIGH)
                return hs;
        return fs;
}


/* debug settings */
#ifdef DEBUG
static int debug = 1;
#else
#define debug 0
#endif

#define gs_debug(format, arg...) \
        do { if (debug) printk(KERN_DEBUG format, ## arg); } while(0)
#define gs_debug_level(level, format, arg...) \
        do { if (debug>=level) printk(KERN_DEBUG format, ## arg); } while(0)


/* Thanks to NetChip Technologies for donating this product ID.
 *
 * DO NOT REUSE THESE IDs with a protocol-incompatible driver!!  Ever!!
 * Instead:  allocate your own, using normal USB-IF procedures.
 */
#define GS_VENDOR_ID                    0x0525  /* NetChip */
#define GS_PRODUCT_ID                   0xa4a6  /* Linux-USB Serial Gadget */
#define GS_CDC_PRODUCT_ID               0xa4a7  /* ... as CDC-ACM */

#define GS_LOG2_NOTIFY_INTERVAL         5       /* 1 << 5 == 32 msec */
#define GS_NOTIFY_MAXPACKET             8


/* Structures */

struct gs_dev;

/* circular buffer */
struct gs_buf {
        unsigned int            buf_size;
        char                    *buf_buf;
        char                    *buf_get;
        char                    *buf_put;
};

/* list of requests */
struct gs_req_entry {
        struct list_head        re_entry;
        struct usb_request      *re_req;
};

/* the port structure holds info for each port, one for each minor number */
struct gs_port {
        struct gs_dev           *port_dev;      /* pointer to device struct */
        struct tty_struct       *port_tty;      /* pointer to tty struct */
        spinlock_t              port_lock;
        int                     port_num;
        int                     port_open_count;
        int                     port_in_use;    /* open/close in progress */
        wait_queue_head_t       port_write_wait;/* waiting to write */
        struct gs_buf           *port_write_buf;
        struct usb_cdc_line_coding      port_line_coding;
};

/* the device structure holds info for the USB device */
struct gs_dev {
        struct usb_gadget       *dev_gadget;    /* gadget device pointer */
        spinlock_t              dev_lock;       /* lock for set/reset config */
        int                     dev_config;     /* configuration number */
        struct usb_ep           *dev_notify_ep; /* address of notify endpoint */
        struct usb_ep           *dev_in_ep;     /* address of in endpoint */
        struct usb_ep           *dev_out_ep;    /* address of out endpoint */
        struct usb_endpoint_descriptor          /* descriptor of notify ep */
                                *dev_notify_ep_desc;
        struct usb_endpoint_descriptor          /* descriptor of in endpoint */
                                *dev_in_ep_desc;
        struct usb_endpoint_descriptor          /* descriptor of out endpoint */
                                *dev_out_ep_desc;
        struct usb_request      *dev_ctrl_req;  /* control request */
        struct list_head        dev_req_list;   /* list of write requests */
        int                     dev_sched_port; /* round robin port scheduled */
        struct gs_port          *dev_port[GS_NUM_PORTS]; /* the ports */
};


/* Functions */

/* module */
static int __init gs_module_init(void);
static void __exit gs_module_exit(void);

/* tty driver */
static int gs_open(struct tty_struct *tty, struct file *file);
static void gs_close(struct tty_struct *tty, struct file *file);
static int gs_write(struct tty_struct *tty,
        const unsigned char *buf, int count);
static void gs_put_char(struct tty_struct *tty, unsigned char ch);
static void gs_flush_chars(struct tty_struct *tty);
static int gs_write_room(struct tty_struct *tty);
static int gs_chars_in_buffer(struct tty_struct *tty);
static void gs_throttle(struct tty_struct * tty);
static void gs_unthrottle(struct tty_struct * tty);
static void gs_break(struct tty_struct *tty, int break_state);
static int  gs_ioctl(struct tty_struct *tty, struct file *file,
        unsigned int cmd, unsigned long arg);
static void gs_set_termios(struct tty_struct *tty, struct ktermios *old);

static int gs_send(struct gs_dev *dev);
static int gs_send_packet(struct gs_dev *dev, char *packet,
        unsigned int size);
static int gs_recv_packet(struct gs_dev *dev, char *packet,
        unsigned int size);
static void gs_read_complete(struct usb_ep *ep, struct usb_request *req);
static void gs_write_complete(struct usb_ep *ep, struct usb_request *req);

/* gadget driver */
static int gs_bind(struct usb_gadget *gadget);
static void gs_unbind(struct usb_gadget *gadget);
static int gs_setup(struct usb_gadget *gadget,
        const struct usb_ctrlrequest *ctrl);
static int gs_setup_standard(struct usb_gadget *gadget,
        const struct usb_ctrlrequest *ctrl);
static int gs_setup_class(struct usb_gadget *gadget,
        const struct usb_ctrlrequest *ctrl);
static void gs_setup_complete(struct usb_ep *ep, struct usb_request *req);
static void gs_disconnect(struct usb_gadget *gadget);
static int gs_set_config(struct gs_dev *dev, unsigned config);
static void gs_reset_config(struct gs_dev *dev);
static int gs_build_config_buf(u8 *buf, struct usb_gadget *g,
                u8 type, unsigned int index, int is_otg);

static struct usb_request *gs_alloc_req(struct usb_ep *ep, unsigned int len,
        gfp_t kmalloc_flags);
static void gs_free_req(struct usb_ep *ep, struct usb_request *req);

static struct gs_req_entry *gs_alloc_req_entry(struct usb_ep *ep, unsigned len,
        gfp_t kmalloc_flags);
static void gs_free_req_entry(struct usb_ep *ep, struct gs_req_entry *req);

static int gs_alloc_ports(struct gs_dev *dev, gfp_t kmalloc_flags);
static void gs_free_ports(struct gs_dev *dev);

/* circular buffer */
static struct gs_buf *gs_buf_alloc(unsigned int size, gfp_t kmalloc_flags);
static void gs_buf_free(struct gs_buf *gb);
static void gs_buf_clear(struct gs_buf *gb);
static unsigned int gs_buf_data_avail(struct gs_buf *gb);
static unsigned int gs_buf_space_avail(struct gs_buf *gb);
static unsigned int gs_buf_put(struct gs_buf *gb, const char *buf,
        unsigned int count);
static unsigned int gs_buf_get(struct gs_buf *gb, char *buf,
        unsigned int count);

/* external functions */
extern int net2280_set_fifo_mode(struct usb_gadget *gadget, int mode);


/* Globals */

static struct gs_dev *gs_device;

static const char *EP_IN_NAME;
static const char *EP_OUT_NAME;
static const char *EP_NOTIFY_NAME;

static struct mutex gs_open_close_lock[GS_NUM_PORTS];

static unsigned int read_q_size = GS_DEFAULT_READ_Q_SIZE;
static unsigned int write_q_size = GS_DEFAULT_WRITE_Q_SIZE;

static unsigned int write_buf_size = GS_DEFAULT_WRITE_BUF_SIZE;

static unsigned int use_acm = GS_DEFAULT_USE_ACM;


/* tty driver struct */
static const struct tty_operations gs_tty_ops = {
        .open =                 gs_open,
        .close =                gs_close,
        .write =                gs_write,
        .put_char =             gs_put_char,
        .flush_chars =          gs_flush_chars,
        .write_room =           gs_write_room,
        .ioctl =                gs_ioctl,
        .set_termios =          gs_set_termios,
        .throttle =             gs_throttle,
        .unthrottle =           gs_unthrottle,
        .break_ctl =            gs_break,
        .chars_in_buffer =      gs_chars_in_buffer,
};
static struct tty_driver *gs_tty_driver;

/* gadget driver struct */
static struct usb_gadget_driver gs_gadget_driver = {
#ifdef CONFIG_USB_GADGET_DUALSPEED
        .speed =                USB_SPEED_HIGH,
#else
        .speed =                USB_SPEED_FULL,
#endif /* CONFIG_USB_GADGET_DUALSPEED */
        .function =             GS_LONG_NAME,
        .bind =                 gs_bind,
        .unbind =               gs_unbind,
        .setup =                gs_setup,
        .disconnect =           gs_disconnect,
        .driver = {
                .name =         GS_SHORT_NAME,
        },
};


/* USB descriptors */

#define GS_MANUFACTURER_STR_ID  1
#define GS_PRODUCT_STR_ID       2
#define GS_SERIAL_STR_ID        3
#define GS_BULK_CONFIG_STR_ID   4
#define GS_ACM_CONFIG_STR_ID    5
#define GS_CONTROL_STR_ID       6
#define GS_DATA_STR_ID          7

/* static strings, in UTF-8 */
static char manufacturer[50];
static struct usb_string gs_strings[] = {
        { GS_MANUFACTURER_STR_ID, manufacturer },
        { GS_PRODUCT_STR_ID, GS_LONG_NAME },
        { GS_SERIAL_STR_ID, "0" },
        { GS_BULK_CONFIG_STR_ID, "Gadget Serial Bulk" },
        { GS_ACM_CONFIG_STR_ID, "Gadget Serial CDC ACM" },
        { GS_CONTROL_STR_ID, "Gadget Serial Control" },
        { GS_DATA_STR_ID, "Gadget Serial Data" },
        {  } /* end of list */
};

static struct usb_gadget_strings gs_string_table = {
        .language =             0x0409, /* en-us */
        .strings =              gs_strings,
};

static struct usb_device_descriptor gs_device_desc = {
        .bLength =              USB_DT_DEVICE_SIZE,
        .bDescriptorType =      USB_DT_DEVICE,
        .bcdUSB =               __constant_cpu_to_le16(0x0200),
        .bDeviceSubClass =      0,
        .bDeviceProtocol =      0,
        .idVendor =             __constant_cpu_to_le16(GS_VENDOR_ID),
        .idProduct =            __constant_cpu_to_le16(GS_PRODUCT_ID),
        .iManufacturer =        GS_MANUFACTURER_STR_ID,
        .iProduct =             GS_PRODUCT_STR_ID,
        .iSerialNumber =        GS_SERIAL_STR_ID,
        .bNumConfigurations =   GS_NUM_CONFIGS,
};

static struct usb_otg_descriptor gs_otg_descriptor = {
        .bLength =              sizeof(gs_otg_descriptor),
        .bDescriptorType =      USB_DT_OTG,
        .bmAttributes =         USB_OTG_SRP,
};

static struct usb_config_descriptor gs_bulk_config_desc = {
        .bLength =              USB_DT_CONFIG_SIZE,
        .bDescriptorType =      USB_DT_CONFIG,
        /* .wTotalLength computed dynamically */
        .bNumInterfaces =       1,
        .bConfigurationValue =  GS_BULK_CONFIG_ID,
        .iConfiguration =       GS_BULK_CONFIG_STR_ID,
        .bmAttributes =         USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER,
        .bMaxPower =            1,
};

static struct usb_config_descriptor gs_acm_config_desc = {
        .bLength =              USB_DT_CONFIG_SIZE,
        .bDescriptorType =      USB_DT_CONFIG,
        /* .wTotalLength computed dynamically */
        .bNumInterfaces =       2,
        .bConfigurationValue =  GS_ACM_CONFIG_ID,
        .iConfiguration =       GS_ACM_CONFIG_STR_ID,
        .bmAttributes =         USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER,
        .bMaxPower =            1,
};

static const struct usb_interface_descriptor gs_bulk_interface_desc = {
        .bLength =              USB_DT_INTERFACE_SIZE,
        .bDescriptorType =      USB_DT_INTERFACE,
        .bInterfaceNumber =     GS_BULK_INTERFACE_ID,
        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_CDC_DATA,
        .bInterfaceSubClass =   0,
        .bInterfaceProtocol =   0,
        .iInterface =           GS_DATA_STR_ID,
};

static const struct usb_interface_descriptor gs_control_interface_desc = {
        .bLength =              USB_DT_INTERFACE_SIZE,
        .bDescriptorType =      USB_DT_INTERFACE,
        .bInterfaceNumber =     GS_CONTROL_INTERFACE_ID,
        .bNumEndpoints =        1,
        .bInterfaceClass =      USB_CLASS_COMM,
        .bInterfaceSubClass =   USB_CDC_SUBCLASS_ACM,
        .bInterfaceProtocol =   USB_CDC_ACM_PROTO_AT_V25TER,
        .iInterface =           GS_CONTROL_STR_ID,
};

static const struct usb_interface_descriptor gs_data_interface_desc = {
        .bLength =              USB_DT_INTERFACE_SIZE,
        .bDescriptorType =      USB_DT_INTERFACE,
        .bInterfaceNumber =     GS_DATA_INTERFACE_ID,
        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_CDC_DATA,
        .bInterfaceSubClass =   0,
        .bInterfaceProtocol =   0,
        .iInterface =           GS_DATA_STR_ID,
};

static const struct usb_cdc_header_desc gs_header_desc = {
        .bLength =              sizeof(gs_header_desc),
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_HEADER_TYPE,
        .bcdCDC =               __constant_cpu_to_le16(0x0110),
};

static const struct usb_cdc_call_mgmt_descriptor gs_call_mgmt_descriptor = {
        .bLength =              sizeof(gs_call_mgmt_descriptor),
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_CALL_MANAGEMENT_TYPE,
        .bmCapabilities =       0,
        .bDataInterface =       1,      /* index of data interface */
};

static struct usb_cdc_acm_descriptor gs_acm_descriptor = {
        .bLength =              sizeof(gs_acm_descriptor),
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_ACM_TYPE,
        .bmCapabilities =       0,
};

static const struct usb_cdc_union_desc gs_union_desc = {
        .bLength =              sizeof(gs_union_desc),
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_UNION_TYPE,
        .bMasterInterface0 =    0,      /* index of control interface */
        .bSlaveInterface0 =     1,      /* index of data interface */
};

static struct usb_endpoint_descriptor gs_fullspeed_notify_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       __constant_cpu_to_le16(GS_NOTIFY_MAXPACKET),
        .bInterval =            1 << GS_LOG2_NOTIFY_INTERVAL,
};

static struct usb_endpoint_descriptor gs_fullspeed_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static struct usb_endpoint_descriptor gs_fullspeed_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_OUT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static const struct usb_descriptor_header *gs_bulk_fullspeed_function[] = {
        (struct usb_descriptor_header *) &gs_otg_descriptor,
        (struct usb_descriptor_header *) &gs_bulk_interface_desc,
        (struct usb_descriptor_header *) &gs_fullspeed_in_desc,
        (struct usb_descriptor_header *) &gs_fullspeed_out_desc,
        NULL,
};

static const struct usb_descriptor_header *gs_acm_fullspeed_function[] = {
        (struct usb_descriptor_header *) &gs_otg_descriptor,
        (struct usb_descriptor_header *) &gs_control_interface_desc,
        (struct usb_descriptor_header *) &gs_header_desc,
        (struct usb_descriptor_header *) &gs_call_mgmt_descriptor,
        (struct usb_descriptor_header *) &gs_acm_descriptor,
        (struct usb_descriptor_header *) &gs_union_desc,
        (struct usb_descriptor_header *) &gs_fullspeed_notify_desc,
        (struct usb_descriptor_header *) &gs_data_interface_desc,
        (struct usb_descriptor_header *) &gs_fullspeed_in_desc,
        (struct usb_descriptor_header *) &gs_fullspeed_out_desc,
        NULL,
};

static struct usb_endpoint_descriptor gs_highspeed_notify_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       __constant_cpu_to_le16(GS_NOTIFY_MAXPACKET),
        .bInterval =            GS_LOG2_NOTIFY_INTERVAL+4,
};

static struct usb_endpoint_descriptor gs_highspeed_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       __constant_cpu_to_le16(512),
};

static struct usb_endpoint_descriptor gs_highspeed_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       __constant_cpu_to_le16(512),
};

static struct usb_qualifier_descriptor gs_qualifier_desc = {
        .bLength =              sizeof(struct usb_qualifier_descriptor),
        .bDescriptorType =      USB_DT_DEVICE_QUALIFIER,
        .bcdUSB =               __constant_cpu_to_le16 (0x0200),
        /* assumes ep0 uses the same value for both speeds ... */
        .bNumConfigurations =   GS_NUM_CONFIGS,
};

static const struct usb_descriptor_header *gs_bulk_highspeed_function[] = {
        (struct usb_descriptor_header *) &gs_otg_descriptor,
        (struct usb_descriptor_header *) &gs_bulk_interface_desc,
        (struct usb_descriptor_header *) &gs_highspeed_in_desc,
        (struct usb_descriptor_header *) &gs_highspeed_out_desc,
        NULL,
};

static const struct usb_descriptor_header *gs_acm_highspeed_function[] = {
        (struct usb_descriptor_header *) &gs_otg_descriptor,
        (struct usb_descriptor_header *) &gs_control_interface_desc,
        (struct usb_descriptor_header *) &gs_header_desc,
        (struct usb_descriptor_header *) &gs_call_mgmt_descriptor,
        (struct usb_descriptor_header *) &gs_acm_descriptor,
        (struct usb_descriptor_header *) &gs_union_desc,
        (struct usb_descriptor_header *) &gs_highspeed_notify_desc,
        (struct usb_descriptor_header *) &gs_data_interface_desc,
        (struct usb_descriptor_header *) &gs_highspeed_in_desc,
        (struct usb_descriptor_header *) &gs_highspeed_out_desc,
        NULL,
};


/* Module */
MODULE_DESCRIPTION(GS_LONG_NAME);
MODULE_AUTHOR("Al Borchers");
MODULE_LICENSE("GPL");

#ifdef DEBUG
module_param(debug, int, S_IRUGO|S_IWUSR);
MODULE_PARM_DESC(debug, "Enable debugging, 0=off, 1=on");
#endif

module_param(read_q_size, uint, S_IRUGO);
MODULE_PARM_DESC(read_q_size, "Read request queue size, default=32");

module_param(write_q_size, uint, S_IRUGO);
MODULE_PARM_DESC(write_q_size, "Write request queue size, default=32");

module_param(write_buf_size, uint, S_IRUGO);
MODULE_PARM_DESC(write_buf_size, "Write buffer size, default=8192");

module_param(use_acm, uint, S_IRUGO);
MODULE_PARM_DESC(use_acm, "Use CDC ACM, 0=no, 1=yes, default=no");

module_init(gs_module_init);
module_exit(gs_module_exit);

/*
*  gs_module_init
*
*  Register as a USB gadget driver and a tty driver.
*/
static int __init gs_module_init(void)
{
        int i;
        int retval;

        retval = usb_gadget_register_driver(&gs_gadget_driver);
        if (retval) {
                printk(KERN_ERR "gs_module_init: cannot register gadget driver, ret=%d\n", retval);
                return retval;
        }

        gs_tty_driver = alloc_tty_driver(GS_NUM_PORTS);
        if (!gs_tty_driver)
                return -ENOMEM;
        gs_tty_driver->owner = THIS_MODULE;
        gs_tty_driver->driver_name = GS_SHORT_NAME;
        gs_tty_driver->name = "ttygs";
        gs_tty_driver->major = GS_MAJOR;
        gs_tty_driver->minor_start = GS_MINOR_START;
        gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
        gs_tty_driver->subtype = SERIAL_TYPE_NORMAL;
        gs_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
        gs_tty_driver->init_termios = tty_std_termios;
        gs_tty_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;
        tty_set_operations(gs_tty_driver, &gs_tty_ops);

        for (i=0; i < GS_NUM_PORTS; i++)
                mutex_init(&gs_open_close_lock[i]);

        retval = tty_register_driver(gs_tty_driver);
        if (retval) {
                usb_gadget_unregister_driver(&gs_gadget_driver);
                put_tty_driver(gs_tty_driver);
                printk(KERN_ERR "gs_module_init: cannot register tty driver, ret=%d\n", retval);
                return retval;
        }

        printk(KERN_INFO "gs_module_init: %s %s loaded\n", GS_LONG_NAME, GS_VERSION_STR);
        return 0;
}

/*
* gs_module_exit
*
* Unregister as a tty driver and a USB gadget driver.
*/
static void __exit gs_module_exit(void)
{
        tty_unregister_driver(gs_tty_driver);
        put_tty_driver(gs_tty_driver);
        usb_gadget_unregister_driver(&gs_gadget_driver);

        printk(KERN_INFO "gs_module_exit: %s %s unloaded\n", GS_LONG_NAME, GS_VERSION_STR);
}

/* TTY Driver */

/*
 * gs_open
 */
static int gs_open(struct tty_struct *tty, struct file *file)
{
        int port_num;
        unsigned long flags;
        struct gs_port *port;
        struct gs_dev *dev;
        struct gs_buf *buf;
        struct mutex *mtx;
        int ret;

        port_num = tty->index;

        gs_debug("gs_open: (%d,%p,%p)\n", port_num, tty, file);

        if (port_num < 0 || port_num >= GS_NUM_PORTS) {
                printk(KERN_ERR "gs_open: (%d,%p,%p) invalid port number\n",
                        port_num, tty, file);
                return -ENODEV;
        }

        dev = gs_device;

        if (dev == NULL) {
                printk(KERN_ERR "gs_open: (%d,%p,%p) NULL device pointer\n",
                        port_num, tty, file);
                return -ENODEV;
        }

        mtx = &gs_open_close_lock[port_num];
        if (mutex_lock_interruptible(mtx)) {
                printk(KERN_ERR
                "gs_open: (%d,%p,%p) interrupted waiting for mutex\n",
                        port_num, tty, file);
                return -ERESTARTSYS;
        }

        spin_lock_irqsave(&dev->dev_lock, flags);

        if (dev->dev_config == GS_NO_CONFIG_ID) {
                printk(KERN_ERR
                        "gs_open: (%d,%p,%p) device is not connected\n",
                        port_num, tty, file);
                ret = -ENODEV;
                goto exit_unlock_dev;
        }

        port = dev->dev_port[port_num];

        if (port == NULL) {
                printk(KERN_ERR "gs_open: (%d,%p,%p) NULL port pointer\n",
                        port_num, tty, file);
                ret = -ENODEV;
                goto exit_unlock_dev;
        }

        spin_lock(&port->port_lock);
        spin_unlock(&dev->dev_lock);

        if (port->port_dev == NULL) {
                printk(KERN_ERR "gs_open: (%d,%p,%p) port disconnected (1)\n",
                        port_num, tty, file);
                ret = -EIO;
                goto exit_unlock_port;
        }

        if (port->port_open_count > 0) {
                ++port->port_open_count;
                gs_debug("gs_open: (%d,%p,%p) already open\n",
                        port_num, tty, file);
                ret = 0;
                goto exit_unlock_port;
        }

        tty->driver_data = NULL;

        /* mark port as in use, we can drop port lock and sleep if necessary */
        port->port_in_use = 1;

        /* allocate write buffer on first open */
        if (port->port_write_buf == NULL) {
                spin_unlock_irqrestore(&port->port_lock, flags);
                buf = gs_buf_alloc(write_buf_size, GFP_KERNEL);
                spin_lock_irqsave(&port->port_lock, flags);

                /* might have been disconnected while asleep, check */
                if (port->port_dev == NULL) {
                        printk(KERN_ERR
                                "gs_open: (%d,%p,%p) port disconnected (2)\n",
                                port_num, tty, file);
                        port->port_in_use = 0;
                        ret = -EIO;
                        goto exit_unlock_port;
                }

                if ((port->port_write_buf=buf) == NULL) {
                        printk(KERN_ERR "gs_open: (%d,%p,%p) cannot allocate port write buffer\n",
                                port_num, tty, file);
                        port->port_in_use = 0;
                        ret = -ENOMEM;
                        goto exit_unlock_port;
                }

        }

        /* wait for carrier detect (not implemented) */

        /* might have been disconnected while asleep, check */
        if (port->port_dev == NULL) {
                printk(KERN_ERR "gs_open: (%d,%p,%p) port disconnected (3)\n",
                        port_num, tty, file);
                port->port_in_use = 0;
                ret = -EIO;
                goto exit_unlock_port;
        }

        tty->driver_data = port;
        port->port_tty = tty;
        port->port_open_count = 1;
        port->port_in_use = 0;

        gs_debug("gs_open: (%d,%p,%p) completed\n", port_num, tty, file);

        ret = 0;

exit_unlock_port:
        spin_unlock_irqrestore(&port->port_lock, flags);
        mutex_unlock(mtx);
        return ret;

exit_unlock_dev:
        spin_unlock_irqrestore(&dev->dev_lock, flags);
        mutex_unlock(mtx);
        return ret;

}

/*
 * gs_close
 */

#define GS_WRITE_FINISHED_EVENT_SAFELY(p)                       \
({                                                              \
        int cond;                                               \
                                                                \
        spin_lock_irq(&(p)->port_lock);                         \
        cond = !(p)->port_dev || !gs_buf_data_avail((p)->port_write_buf); \
        spin_unlock_irq(&(p)->port_lock);                       \
        cond;                                                   \
})

static void gs_close(struct tty_struct *tty, struct file *file)
{
        struct gs_port *port = tty->driver_data;
        struct mutex *mtx;

        if (port == NULL) {
                printk(KERN_ERR "gs_close: NULL port pointer\n");
                return;
        }

        gs_debug("gs_close: (%d,%p,%p)\n", port->port_num, tty, file);

        mtx = &gs_open_close_lock[port->port_num];
        mutex_lock(mtx);

        spin_lock_irq(&port->port_lock);

        if (port->port_open_count == 0) {
                printk(KERN_ERR
                        "gs_close: (%d,%p,%p) port is already closed\n",
                        port->port_num, tty, file);
                goto exit;
        }

        if (port->port_open_count > 1) {
                --port->port_open_count;
                goto exit;
        }

        /* free disconnected port on final close */
        if (port->port_dev == NULL) {
                kfree(port);
                goto exit;
        }

        /* mark port as closed but in use, we can drop port lock */
        /* and sleep if necessary */
        port->port_in_use = 1;
        port->port_open_count = 0;

        /* wait for write buffer to drain, or */
        /* at most GS_CLOSE_TIMEOUT seconds */
        if (gs_buf_data_avail(port->port_write_buf) > 0) {
                spin_unlock_irq(&port->port_lock);
                wait_event_interruptible_timeout(port->port_write_wait,
                                        GS_WRITE_FINISHED_EVENT_SAFELY(port),
                                        GS_CLOSE_TIMEOUT * HZ);
                spin_lock_irq(&port->port_lock);
        }

        /* free disconnected port on final close */
        /* (might have happened during the above sleep) */
        if (port->port_dev == NULL) {
                kfree(port);
                goto exit;
        }

        gs_buf_clear(port->port_write_buf);

        tty->driver_data = NULL;
        port->port_tty = NULL;
        port->port_in_use = 0;

        gs_debug("gs_close: (%d,%p,%p) completed\n",
                port->port_num, tty, file);

exit:
        spin_unlock_irq(&port->port_lock);
        mutex_unlock(mtx);
}

/*
 * gs_write
 */
static int gs_write(struct tty_struct *tty, const unsigned char *buf, int count)
{
        unsigned long flags;
        struct gs_port *port = tty->driver_data;
        int ret;

        if (port == NULL) {
                printk(KERN_ERR "gs_write: NULL port pointer\n");
                return -EIO;
        }

        gs_debug("gs_write: (%d,%p) writing %d bytes\n", port->port_num, tty,
                count);

        if (count == 0)
                return 0;

        spin_lock_irqsave(&port->port_lock, flags);

        if (port->port_dev == NULL) {
                printk(KERN_ERR "gs_write: (%d,%p) port is not connected\n",
                        port->port_num, tty);
                ret = -EIO;
                goto exit;
        }

        if (port->port_open_count == 0) {
                printk(KERN_ERR "gs_write: (%d,%p) port is closed\n",
                        port->port_num, tty);
                ret = -EBADF;
                goto exit;
        }

        count = gs_buf_put(port->port_write_buf, buf, count);

        spin_unlock_irqrestore(&port->port_lock, flags);

        gs_send(gs_device);

        gs_debug("gs_write: (%d,%p) wrote %d bytes\n", port->port_num, tty,
                count);

        return count;

exit:
        spin_unlock_irqrestore(&port->port_lock, flags);
        return ret;
}

/*
 * gs_put_char
 */
static void gs_put_char(struct tty_struct *tty, unsigned char ch)
{
        unsigned long flags;
        struct gs_port *port = tty->driver_data;

        if (port == NULL) {
                printk(KERN_ERR "gs_put_char: NULL port pointer\n");
                return;
        }

        gs_debug("gs_put_char: (%d,%p) char=0x%x, called from %p\n",
                port->port_num, tty, ch, __builtin_return_address(0));

        spin_lock_irqsave(&port->port_lock, flags);

        if (port->port_dev == NULL) {
                printk(KERN_ERR "gs_put_char: (%d,%p) port is not connected\n",
                        port->port_num, tty);
                goto exit;
        }

        if (port->port_open_count == 0) {
                printk(KERN_ERR "gs_put_char: (%d,%p) port is closed\n",
                        port->port_num, tty);
                goto exit;
        }

        gs_buf_put(port->port_write_buf, &ch, 1);

exit:
        spin_unlock_irqrestore(&port->port_lock, flags);
}

/*
 * gs_flush_chars
 */
static void gs_flush_chars(struct tty_struct *tty)
{
        unsigned long flags;
        struct gs_port *port = tty->driver_data;

        if (port == NULL) {
                printk(KERN_ERR "gs_flush_chars: NULL port pointer\n");
                return;
        }

        gs_debug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);

        spin_lock_irqsave(&port->port_lock, flags);

        if (port->port_dev == NULL) {
                printk(KERN_ERR
                        "gs_flush_chars: (%d,%p) port is not connected\n",
                        port->port_num, tty);
                goto exit;
        }

        if (port->port_open_count == 0) {
                printk(KERN_ERR "gs_flush_chars: (%d,%p) port is closed\n",
                        port->port_num, tty);
                goto exit;
        }

        spin_unlock_irqrestore(&port->port_lock, flags);

        gs_send(gs_device);

        return;

exit:
        spin_unlock_irqrestore(&port->port_lock, flags);
}

/*
 * gs_write_room
 */
static int gs_write_room(struct tty_struct *tty)
{

        int room = 0;
        unsigned long flags;
        struct gs_port *port = tty->driver_data;


        if (port == NULL)
                return 0;

        spin_lock_irqsave(&port->port_lock, flags);

        if (port->port_dev != NULL && port->port_open_count > 0
        && port->port_write_buf != NULL)
                room = gs_buf_space_avail(port->port_write_buf);

        spin_unlock_irqrestore(&port->port_lock, flags);

        gs_debug("gs_write_room: (%d,%p) room=%d\n",
                port->port_num, tty, room);

        return room;
}

/*
 * gs_chars_in_buffer
 */
static int gs_chars_in_buffer(struct tty_struct *tty)
{
        int chars = 0;
        unsigned long flags;
        struct gs_port *port = tty->driver_data;

        if (port == NULL)
                return 0;

        spin_lock_irqsave(&port->port_lock, flags);

        if (port->port_dev != NULL && port->port_open_count > 0

        && port->port_write_buf != NULL)
                chars = gs_buf_data_avail(port->port_write_buf);

        spin_unlock_irqrestore(&port->port_lock, flags);

        gs_debug("gs_chars_in_buffer: (%d,%p) chars=%d\n",
                port->port_num, tty, chars);

        return chars;
}

/*
 * gs_throttle
 */
static void gs_throttle(struct tty_struct *tty)
{
}

/*
 * gs_unthrottle
 */
static void gs_unthrottle(struct tty_struct *tty)
{
}

/*
 * gs_break
 */
static void gs_break(struct tty_struct *tty, int break_state)
{
}

/*
 * gs_ioctl
 */
static int gs_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg)
{
        struct gs_port *port = tty->driver_data;

        if (port == NULL) {
                printk(KERN_ERR "gs_ioctl: NULL port pointer\n");
                return -EIO;
        }

        gs_debug("gs_ioctl: (%d,%p,%p) cmd=0x%4.4x, arg=%lu\n",
                port->port_num, tty, file, cmd, arg);

        /* handle ioctls */

        /* could not handle ioctl */
        return -ENOIOCTLCMD;
}

/*
 * gs_set_termios
 */
static void gs_set_termios(struct tty_struct *tty, struct ktermios *old)
{
}

/*
* gs_send
*
* This function finds available write requests, calls
* gs_send_packet to fill these packets with data, and
* continues until either there are no more write requests
* available or no more data to send.  This function is
* run whenever data arrives or write requests are available.
*/
static int gs_send(struct gs_dev *dev)
{
        int ret,len;
        unsigned long flags;
        struct usb_ep *ep;
        struct usb_request *req;
        struct gs_req_entry *req_entry;

        if (dev == NULL) {
                printk(KERN_ERR "gs_send: NULL device pointer\n");
                return -ENODEV;
        }

        spin_lock_irqsave(&dev->dev_lock, flags);

        ep = dev->dev_in_ep;

        while(!list_empty(&dev->dev_req_list)) {

                req_entry = list_entry(dev->dev_req_list.next,
                        struct gs_req_entry, re_entry);

                req = req_entry->re_req;

                len = gs_send_packet(dev, req->buf, ep->maxpacket);

                if (len > 0) {
                        gs_debug_level(3, "gs_send: len=%d, 0x%2.2x "
                                        "0x%2.2x 0x%2.2x ...\n", len,
                                        *((unsigned char *)req->buf),
                                        *((unsigned char *)req->buf+1),
                                        *((unsigned char *)req->buf+2));
                        list_del(&req_entry->re_entry);
                        req->length = len;
                        spin_unlock_irqrestore(&dev->dev_lock, flags);
                        if ((ret=usb_ep_queue(ep, req, GFP_ATOMIC))) {
                                printk(KERN_ERR
                                "gs_send: cannot queue read request, ret=%d\n",
                                        ret);
                                spin_lock_irqsave(&dev->dev_lock, flags);
                                break;
                        }
                        spin_lock_irqsave(&dev->dev_lock, flags);
                } else {
                        break;
                }

        }

        spin_unlock_irqrestore(&dev->dev_lock, flags);

        return 0;
}

/*
 * gs_send_packet
 *
 * If there is data to send, a packet is built in the given
 * buffer and the size is returned.  If there is no data to
 * send, 0 is returned.  If there is any error a negative
 * error number is returned.
 *
 * Called during USB completion routine, on interrupt time.
 *
 * We assume that disconnect will not happen until all completion
 * routines have completed, so we can assume that the dev_port
 * array does not change during the lifetime of this function.
 */
static int gs_send_packet(struct gs_dev *dev, char *packet, unsigned int size)
{
        unsigned int len;
        struct gs_port *port;

        /* TEMPORARY -- only port 0 is supported right now */
        port = dev->dev_port[0];

        if (port == NULL) {
                printk(KERN_ERR
                        "gs_send_packet: port=%d, NULL port pointer\n",
                        0);
                return -EIO;
        }

        spin_lock(&port->port_lock);

        len = gs_buf_data_avail(port->port_write_buf);
        if (len < size)
                size = len;

        if (size == 0)
                goto exit;

        size = gs_buf_get(port->port_write_buf, packet, size);

        if (port->port_tty)
                wake_up_interruptible(&port->port_tty->write_wait);

exit:
        spin_unlock(&port->port_lock);
        return size;
}

/*
 * gs_recv_packet
 *
 * Called for each USB packet received.  Reads the packet
 * header and stuffs the data in the appropriate tty buffer.
 * Returns 0 if successful, or a negative error number.
 *
 * Called during USB completion routine, on interrupt time.
 *
 * We assume that disconnect will not happen until all completion
 * routines have completed, so we can assume that the dev_port
 * array does not change during the lifetime of this function.
 */
static int gs_recv_packet(struct gs_dev *dev, char *packet, unsigned int size)
{
        unsigned int len;
        struct gs_port *port;
        int ret;
        struct tty_struct *tty;

        /* TEMPORARY -- only port 0 is supported right now */
        port = dev->dev_port[0];

        if (port == NULL) {
                printk(KERN_ERR "gs_recv_packet: port=%d, NULL port pointer\n",
                        port->port_num);
                return -EIO;
        }

        spin_lock(&port->port_lock);

        if (port->port_open_count == 0) {
                printk(KERN_ERR "gs_recv_packet: port=%d, port is closed\n",
                        port->port_num);
                ret = -EIO;
                goto exit;
        }


        tty = port->port_tty;

        if (tty == NULL) {
                printk(KERN_ERR "gs_recv_packet: port=%d, NULL tty pointer\n",
                        port->port_num);
                ret = -EIO;
                goto exit;
        }

        if (port->port_tty->magic != TTY_MAGIC) {
                printk(KERN_ERR "gs_recv_packet: port=%d, bad tty magic\n",
                        port->port_num);
                ret = -EIO;
                goto exit;
        }

        len = tty_buffer_request_room(tty, size);
        if (len > 0) {
                tty_insert_flip_string(tty, packet, len);
                tty_flip_buffer_push(port->port_tty);
                wake_up_interruptible(&port->port_tty->read_wait);
        }
        ret = 0;
exit:
        spin_unlock(&port->port_lock);
        return ret;
}

/*
* gs_read_complete
*/
static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
{
        int ret;
        struct gs_dev *dev = ep->driver_data;

        if (dev == NULL) {
                printk(KERN_ERR "gs_read_complete: NULL device pointer\n");
                return;
        }

        switch(req->status) {
        case 0:
                /* normal completion */
                gs_recv_packet(dev, req->buf, req->actual);
requeue:
                req->length = ep->maxpacket;
                if ((ret=usb_ep_queue(ep, req, GFP_ATOMIC))) {
                        printk(KERN_ERR
                        "gs_read_complete: cannot queue read request, ret=%d\n",
                                ret);
                }
                break;

        case -ESHUTDOWN:
                /* disconnect */
                gs_debug("gs_read_complete: shutdown\n");
                gs_free_req(ep, req);
                break;

        default:
                /* unexpected */
                printk(KERN_ERR
                "gs_read_complete: unexpected status error, status=%d\n",
                        req->status);
                goto requeue;
                break;
        }
}

/*
* gs_write_complete
*/
static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct gs_dev *dev = ep->driver_data;
        struct gs_req_entry *gs_req = req->context;

        if (dev == NULL) {
                printk(KERN_ERR "gs_write_complete: NULL device pointer\n");
                return;
        }

        switch(req->status) {
        case 0:
                /* normal completion */
requeue:
                if (gs_req == NULL) {
                        printk(KERN_ERR
                                "gs_write_complete: NULL request pointer\n");
                        return;
                }

                spin_lock(&dev->dev_lock);
                list_add(&gs_req->re_entry, &dev->dev_req_list);
                spin_unlock(&dev->dev_lock);

                gs_send(dev);

                break;

        case -ESHUTDOWN:
                /* disconnect */
                gs_debug("gs_write_complete: shutdown\n");
                gs_free_req(ep, req);
                break;

        default:
                printk(KERN_ERR
                "gs_write_complete: unexpected status error, status=%d\n",
                        req->status);
                goto requeue;
                break;
        }
}

/* Gadget Driver */

/*
 * gs_bind
 *
 * Called on module load.  Allocates and initializes the device
 * structure and a control request.
 */
static int __init gs_bind(struct usb_gadget *gadget)
{
        int ret;
        struct usb_ep *ep;
        struct gs_dev *dev;
        int gcnum;

        /* Some controllers can't support CDC ACM:
         * - sh doesn't support multiple interfaces or configs;
         * - sa1100 doesn't have a third interrupt endpoint
         */
        if (gadget_is_sh(gadget) || gadget_is_sa1100(gadget))
                use_acm = 0;

        gcnum = usb_gadget_controller_number(gadget);
        if (gcnum >= 0)
                gs_device_desc.bcdDevice =
                                cpu_to_le16(GS_VERSION_NUM | gcnum);
        else {
                printk(KERN_WARNING "gs_bind: controller '%s' not recognized\n",
                        gadget->name);
                /* unrecognized, but safe unless bulk is REALLY quirky */
                gs_device_desc.bcdDevice =
                        __constant_cpu_to_le16(GS_VERSION_NUM|0x0099);
        }

        usb_ep_autoconfig_reset(gadget);

        ep = usb_ep_autoconfig(gadget, &gs_fullspeed_in_desc);
        if (!ep)
                goto autoconf_fail;
        EP_IN_NAME = ep->name;
        ep->driver_data = ep;   /* claim the endpoint */

        ep = usb_ep_autoconfig(gadget, &gs_fullspeed_out_desc);
        if (!ep)
                goto autoconf_fail;
        EP_OUT_NAME = ep->name;
        ep->driver_data = ep;   /* claim the endpoint */

        if (use_acm) {
                ep = usb_ep_autoconfig(gadget, &gs_fullspeed_notify_desc);
                if (!ep) {
                        printk(KERN_ERR "gs_bind: cannot run ACM on %s\n", gadget->name);
                        goto autoconf_fail;
                }
                gs_device_desc.idProduct = __constant_cpu_to_le16(
                                                GS_CDC_PRODUCT_ID),
                EP_NOTIFY_NAME = ep->name;
                ep->driver_data = ep;   /* claim the endpoint */
        }

        gs_device_desc.bDeviceClass = use_acm
                ? USB_CLASS_COMM : USB_CLASS_VENDOR_SPEC;
        gs_device_desc.bMaxPacketSize0 = gadget->ep0->maxpacket;

        if (gadget_is_dualspeed(gadget)) {
                gs_qualifier_desc.bDeviceClass = use_acm
                        ? USB_CLASS_COMM : USB_CLASS_VENDOR_SPEC;
                /* assume ep0 uses the same packet size for both speeds */
                gs_qualifier_desc.bMaxPacketSize0 =
                        gs_device_desc.bMaxPacketSize0;
                /* assume endpoints are dual-speed */
                gs_highspeed_notify_desc.bEndpointAddress =
                        gs_fullspeed_notify_desc.bEndpointAddress;
                gs_highspeed_in_desc.bEndpointAddress =
                        gs_fullspeed_in_desc.bEndpointAddress;
                gs_highspeed_out_desc.bEndpointAddress =
                        gs_fullspeed_out_desc.bEndpointAddress;
        }

        usb_gadget_set_selfpowered(gadget);

        if (gadget_is_otg(gadget)) {
                gs_otg_descriptor.bmAttributes |= USB_OTG_HNP,
                gs_bulk_config_desc.bmAttributes |= USB_CONFIG_ATT_WAKEUP;
                gs_acm_config_desc.bmAttributes |= USB_CONFIG_ATT_WAKEUP;
        }

        gs_device = dev = kzalloc(sizeof(struct gs_dev), GFP_KERNEL);
        if (dev == NULL)
                return -ENOMEM;

        snprintf(manufacturer, sizeof(manufacturer), "%s %s with %s",
                init_utsname()->sysname, init_utsname()->release,
                gadget->name);

        dev->dev_gadget = gadget;
        spin_lock_init(&dev->dev_lock);
        INIT_LIST_HEAD(&dev->dev_req_list);
        set_gadget_data(gadget, dev);

        if ((ret=gs_alloc_ports(dev, GFP_KERNEL)) != 0) {
                printk(KERN_ERR "gs_bind: cannot allocate ports\n");
                gs_unbind(gadget);
                return ret;
        }

        /* preallocate control response and buffer */
        dev->dev_ctrl_req = gs_alloc_req(gadget->ep0, GS_MAX_DESC_LEN,
                GFP_KERNEL);
        if (dev->dev_ctrl_req == NULL) {
                gs_unbind(gadget);
                return -ENOMEM;
        }
        dev->dev_ctrl_req->complete = gs_setup_complete;

        gadget->ep0->driver_data = dev;

        printk(KERN_INFO "gs_bind: %s %s bound\n",
                GS_LONG_NAME, GS_VERSION_STR);

        return 0;

autoconf_fail:
        printk(KERN_ERR "gs_bind: cannot autoconfigure on %s\n", gadget->name);
        return -ENODEV;
}

/*
 * gs_unbind
 *
 * Called on module unload.  Frees the control request and device
 * structure.
 */
static void /* __init_or_exit */ gs_unbind(struct usb_gadget *gadget)
{
        struct gs_dev *dev = get_gadget_data(gadget);

        gs_device = NULL;

        /* read/write requests already freed, only control request remains */
        if (dev != NULL) {
                if (dev->dev_ctrl_req != NULL) {
                        gs_free_req(gadget->ep0, dev->dev_ctrl_req);
                        dev->dev_ctrl_req = NULL;
                }
                gs_free_ports(dev);
                if (dev->dev_notify_ep)
                        usb_ep_disable(dev->dev_notify_ep);
                if (dev->dev_in_ep)
                        usb_ep_disable(dev->dev_in_ep);
                if (dev->dev_out_ep)
                        usb_ep_disable(dev->dev_out_ep);
                kfree(dev);
                set_gadget_data(gadget, NULL);
        }

        printk(KERN_INFO "gs_unbind: %s %s unbound\n", GS_LONG_NAME,
                GS_VERSION_STR);
}

/*
 * gs_setup
 *
 * Implements all the control endpoint functionality that's not
 * handled in hardware or the hardware driver.
 *
 * Returns the size of the data sent to the host, or a negative
 * error number.
 */
static int gs_setup(struct usb_gadget *gadget,
        const struct usb_ctrlrequest *ctrl)
{
        int ret = -EOPNOTSUPP;
        struct gs_dev *dev = get_gadget_data(gadget);
        struct usb_request *req = dev->dev_ctrl_req;
        u16 wIndex = le16_to_cpu(ctrl->wIndex);
        u16 wValue = le16_to_cpu(ctrl->wValue);
        u16 wLength = le16_to_cpu(ctrl->wLength);

        switch (ctrl->bRequestType & USB_TYPE_MASK) {
        case USB_TYPE_STANDARD:
                ret = gs_setup_standard(gadget,ctrl);
                break;

        case USB_TYPE_CLASS:
                ret = gs_setup_class(gadget,ctrl);
                break;

        default:
                printk(KERN_ERR "gs_setup: unknown request, type=%02x, request=%02x, value=%04x, index=%04x, length=%d\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        wValue, wIndex, wLength);
                break;
        }

        /* respond with data transfer before status phase? */
        if (ret >= 0) {
                req->length = ret;
                req->zero = ret < wLength
                                && (ret % gadget->ep0->maxpacket) == 0;
                ret = usb_ep_queue(gadget->ep0, req, GFP_ATOMIC);
                if (ret < 0) {
                        printk(KERN_ERR "gs_setup: cannot queue response, ret=%d\n",
                                ret);
                        req->status = 0;
                        gs_setup_complete(gadget->ep0, req);
                }
        }

        /* device either stalls (ret < 0) or reports success */
        return ret;
}

static int gs_setup_standard(struct usb_gadget *gadget,
        const struct usb_ctrlrequest *ctrl)
{
        int ret = -EOPNOTSUPP;
        struct gs_dev *dev = get_gadget_data(gadget);
        struct usb_request *req = dev->dev_ctrl_req;
        u16 wIndex = le16_to_cpu(ctrl->wIndex);
        u16 wValue = le16_to_cpu(ctrl->wValue);
        u16 wLength = le16_to_cpu(ctrl->wLength);

        switch (ctrl->bRequest) {
        case USB_REQ_GET_DESCRIPTOR:
                if (ctrl->bRequestType != USB_DIR_IN)
                        break;

                switch (wValue >> 8) {
                case USB_DT_DEVICE:
                        ret = min(wLength,
                                (u16)sizeof(struct usb_device_descriptor));
                        memcpy(req->buf, &gs_device_desc, ret);
                        break;

                case USB_DT_DEVICE_QUALIFIER:
                        if (!gadget_is_dualspeed(gadget))
                                break;
                        ret = min(wLength,
                                (u16)sizeof(struct usb_qualifier_descriptor));
                        memcpy(req->buf, &gs_qualifier_desc, ret);
                        break;

                case USB_DT_OTHER_SPEED_CONFIG:
                        if (!gadget_is_dualspeed(gadget))
                                break;
                        /* fall through */
                case USB_DT_CONFIG:
                        ret = gs_build_config_buf(req->buf, gadget,
                                wValue >> 8, wValue & 0xff,
                                gadget_is_otg(gadget));
                        if (ret >= 0)
                                ret = min(wLength, (u16)ret);
                        break;

                case USB_DT_STRING:
                        /* wIndex == language code. */
                        ret = usb_gadget_get_string(&gs_string_table,
                                wValue & 0xff, req->buf);
                        if (ret >= 0)
                                ret = min(wLength, (u16)ret);
                        break;
                }
                break;

        case USB_REQ_SET_CONFIGURATION:
                if (ctrl->bRequestType != 0)
                        break;
                spin_lock(&dev->dev_lock);
                ret = gs_set_config(dev, wValue);
                spin_unlock(&dev->dev_lock);
                break;

        case USB_REQ_GET_CONFIGURATION:
                if (ctrl->bRequestType != USB_DIR_IN)
                        break;
                *(u8 *)req->buf = dev->dev_config;
                ret = min(wLength, (u16)1);
                break;

        case USB_REQ_SET_INTERFACE:
                if (ctrl->bRequestType != USB_RECIP_INTERFACE
                                || !dev->dev_config
                                || wIndex >= GS_MAX_NUM_INTERFACES)
                        break;
                if (dev->dev_config == GS_BULK_CONFIG_ID
                                && wIndex != GS_BULK_INTERFACE_ID)
                        break;
                /* no alternate interface settings */
                if (wValue != 0)
                        break;
                spin_lock(&dev->dev_lock);
                /* PXA hardware partially handles SET_INTERFACE;
                 * we need to kluge around that interference.  */
                if (gadget_is_pxa(gadget)) {
                        ret = gs_set_config(dev, use_acm ?
                                GS_ACM_CONFIG_ID : GS_BULK_CONFIG_ID);
                        goto set_interface_done;
                }
                if (dev->dev_config != GS_BULK_CONFIG_ID
                                && wIndex == GS_CONTROL_INTERFACE_ID) {
                        if (dev->dev_notify_ep) {
                                usb_ep_disable(dev->dev_notify_ep);
                                usb_ep_enable(dev->dev_notify_ep, dev->dev_notify_ep_desc);
                        }
                } else {
                        usb_ep_disable(dev->dev_in_ep);
                        usb_ep_disable(dev->dev_out_ep);
                        usb_ep_enable(dev->dev_in_ep, dev->dev_in_ep_desc);
                        usb_ep_enable(dev->dev_out_ep, dev->dev_out_ep_desc);
                }
                ret = 0;
set_interface_done:
                spin_unlock(&dev->dev_lock);
                break;

        case USB_REQ_GET_INTERFACE:
                if (ctrl->bRequestType != (USB_DIR_IN|USB_RECIP_INTERFACE)
                || dev->dev_config == GS_NO_CONFIG_ID)
                        break;
                if (wIndex >= GS_MAX_NUM_INTERFACES
                                || (dev->dev_config == GS_BULK_CONFIG_ID
                                && wIndex != GS_BULK_INTERFACE_ID)) {
                        ret = -EDOM;
                        break;
                }
                /* no alternate interface settings */
                *(u8 *)req->buf = 0;
                ret = min(wLength, (u16)1);
                break;

        default:
                printk(KERN_ERR "gs_setup: unknown standard request, type=%02x, request=%02x, value=%04x, index=%04x, length=%d\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        wValue, wIndex, wLength);
                break;
        }

        return ret;
}

static int gs_setup_class(struct usb_gadget *gadget,
        const struct usb_ctrlrequest *ctrl)
{
        int ret = -EOPNOTSUPP;
        struct gs_dev *dev = get_gadget_data(gadget);
        struct gs_port *port = dev->dev_port[0];        /* ACM only has one port */
        struct usb_request *req = dev->dev_ctrl_req;
        u16 wIndex = le16_to_cpu(ctrl->wIndex);
        u16 wValue = le16_to_cpu(ctrl->wValue);
        u16 wLength = le16_to_cpu(ctrl->wLength);

        switch (ctrl->bRequest) {
        case USB_CDC_REQ_SET_LINE_CODING:
                /* FIXME Submit req to read the data; have its completion
                 * handler copy that data to port->port_line_coding (iff
                 * it's valid) and maybe pass it on.  Until then, fail.
                 */
                printk(KERN_WARNING "gs_setup: set_line_coding "
                                "unuspported\n");
                break;

        case USB_CDC_REQ_GET_LINE_CODING:
                port = dev->dev_port[0];        /* ACM only has one port */
                ret = min(wLength,
                        (u16)sizeof(struct usb_cdc_line_coding));
                if (port) {
                        spin_lock(&port->port_lock);
                        memcpy(req->buf, &port->port_line_coding, ret);
                        spin_unlock(&port->port_lock);
                }
                break;

        case USB_CDC_REQ_SET_CONTROL_LINE_STATE:
                /* FIXME Submit req to read the data; have its completion
                 * handler use that to set the state (iff it's valid) and
                 * maybe pass it on.  Until then, fail.
                 */
                printk(KERN_WARNING "gs_setup: set_control_line_state "
                                "unuspported\n");
                break;

        default:
                printk(KERN_ERR "gs_setup: unknown class request, "
                                "type=%02x, request=%02x, value=%04x, "
                                "index=%04x, length=%d\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        wValue, wIndex, wLength);
                break;
        }

        return ret;
}

/*
 * gs_setup_complete
 */
static void gs_setup_complete(struct usb_ep *ep, struct usb_request *req)
{
        if (req->status || req->actual != req->length) {
                printk(KERN_ERR "gs_setup_complete: status error, status=%d, actual=%d, length=%d\n",
                        req->status, req->actual, req->length);
        }
}

/*
 * gs_disconnect
 *
 * Called when the device is disconnected.  Frees the closed
 * ports and disconnects open ports.  Open ports will be freed
 * on close.  Then reallocates the ports for the next connection.
 */
static void gs_disconnect(struct usb_gadget *gadget)
{
        unsigned long flags;
        struct gs_dev *dev = get_gadget_data(gadget);

        spin_lock_irqsave(&dev->dev_lock, flags);

        gs_reset_config(dev);

        /* free closed ports and disconnect open ports */
        /* (open ports will be freed when closed) */
        gs_free_ports(dev);

        /* re-allocate ports for the next connection */
        if (gs_alloc_ports(dev, GFP_ATOMIC) != 0)
                printk(KERN_ERR "gs_disconnect: cannot re-allocate ports\n");

        spin_unlock_irqrestore(&dev->dev_lock, flags);

        printk(KERN_INFO "gs_disconnect: %s disconnected\n", GS_LONG_NAME);
}

/*
 * gs_set_config
 *
 * Configures the device by enabling device specific
 * optimizations, setting up the endpoints, allocating
 * read and write requests and queuing read requests.
 *
 * The device lock must be held when calling this function.
 */
static int gs_set_config(struct gs_dev *dev, unsigned config)
{
        int i;
        int ret = 0;
        struct usb_gadget *gadget = dev->dev_gadget;
        struct usb_ep *ep;
        struct usb_endpoint_descriptor *ep_desc;
        struct usb_request *req;
        struct gs_req_entry *req_entry;

        if (dev == NULL) {
                printk(KERN_ERR "gs_set_config: NULL device pointer\n");
                return 0;
        }

        if (config == dev->dev_config)
                return 0;

        gs_reset_config(dev);

        switch (config) {
        case GS_NO_CONFIG_ID:
                return 0;
        case GS_BULK_CONFIG_ID:
                if (use_acm)
                        return -EINVAL;
                /* device specific optimizations */
                if (gadget_is_net2280(gadget))
                        net2280_set_fifo_mode(gadget, 1);
                break;
        case GS_ACM_CONFIG_ID:
                if (!use_acm)
                        return -EINVAL;
                /* device specific optimizations */
                if (gadget_is_net2280(gadget))
                        net2280_set_fifo_mode(gadget, 1);
                break;
        default:
                return -EINVAL;
        }

        dev->dev_config = config;

        gadget_for_each_ep(ep, gadget) {

                if (EP_NOTIFY_NAME
                && strcmp(ep->name, EP_NOTIFY_NAME) == 0) {
                        ep_desc = choose_ep_desc(gadget,
                                &gs_highspeed_notify_desc,
                                &gs_fullspeed_notify_desc);
                        ret = usb_ep_enable(ep,ep_desc);
                        if (ret == 0) {
                                ep->driver_data = dev;
                                dev->dev_notify_ep = ep;
                                dev->dev_notify_ep_desc = ep_desc;
                        } else {
                                printk(KERN_ERR "gs_set_config: cannot enable notify endpoint %s, ret=%d\n",
                                        ep->name, ret);
                                goto exit_reset_config;
                        }
                }

                else if (strcmp(ep->name, EP_IN_NAME) == 0) {
                        ep_desc = choose_ep_desc(gadget,
                                &gs_highspeed_in_desc,
                                &gs_fullspeed_in_desc);
                        ret = usb_ep_enable(ep,ep_desc);
                        if (ret == 0) {
                                ep->driver_data = dev;
                                dev->dev_in_ep = ep;
                                dev->dev_in_ep_desc = ep_desc;
                        } else {
                                printk(KERN_ERR "gs_set_config: cannot enable in endpoint %s, ret=%d\n",
                                        ep->name, ret);
                                goto exit_reset_config;
                        }
                }

                else if (strcmp(ep->name, EP_OUT_NAME) == 0) {
                        ep_desc = choose_ep_desc(gadget,
                                &gs_highspeed_out_desc,
                                &gs_fullspeed_out_desc);
                        ret = usb_ep_enable(ep,ep_desc);
                        if (ret == 0) {
                                ep->driver_data = dev;
                                dev->dev_out_ep = ep;
                                dev->dev_out_ep_desc = ep_desc;
                        } else {
                                printk(KERN_ERR "gs_set_config: cannot enable out endpoint %s, ret=%d\n",
                                        ep->name, ret);
                                goto exit_reset_config;
                        }
                }

        }

        if (dev->dev_in_ep == NULL || dev->dev_out_ep == NULL
        || (config != GS_BULK_CONFIG_ID && dev->dev_notify_ep == NULL)) {
                printk(KERN_ERR "gs_set_config: cannot find endpoints\n");
                ret = -ENODEV;
                goto exit_reset_config;
        }

        /* allocate and queue read requests */
        ep = dev->dev_out_ep;
        for (i=0; i<read_q_size && ret == 0; i++) {
                if ((req=gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC))) {
                        req->complete = gs_read_complete;
                        if ((ret=usb_ep_queue(ep, req, GFP_ATOMIC))) {
                                printk(KERN_ERR "gs_set_config: cannot queue read request, ret=%d\n",
                                        ret);
                        }
                } else {
                        printk(KERN_ERR "gs_set_config: cannot allocate read requests\n");
                        ret = -ENOMEM;
                        goto exit_reset_config;
                }
        }

        /* allocate write requests, and put on free list */
        ep = dev->dev_in_ep;
        for (i=0; i<write_q_size; i++) {
                if ((req_entry=gs_alloc_req_entry(ep, ep->maxpacket, GFP_ATOMIC))) {
                        req_entry->re_req->complete = gs_write_complete;
                        list_add(&req_entry->re_entry, &dev->dev_req_list);
                } else {
                        printk(KERN_ERR "gs_set_config: cannot allocate write requests\n");
                        ret = -ENOMEM;
                        goto exit_reset_config;
                }
        }

        printk(KERN_INFO "gs_set_config: %s configured, %s speed %s config\n",
                GS_LONG_NAME,
                gadget->speed == USB_SPEED_HIGH ? "high" : "full",
                config == GS_BULK_CONFIG_ID ? "BULK" : "CDC-ACM");

        return 0;

exit_reset_config:
        gs_reset_config(dev);
        return ret;
}

/*
 * gs_reset_config
 *
 * Mark the device as not configured, disable all endpoints,
 * which forces completion of pending I/O and frees queued
 * requests, and free the remaining write requests on the
 * free list.
 *
 * The device lock must be held when calling this function.
 */
static void gs_reset_config(struct gs_dev *dev)
{
        struct gs_req_entry *req_entry;

        if (dev == NULL) {
                printk(KERN_ERR "gs_reset_config: NULL device pointer\n");
                return;
        }

        if (dev->dev_config == GS_NO_CONFIG_ID)
                return;

        dev->dev_config = GS_NO_CONFIG_ID;

        /* free write requests on the free list */
        while(!list_empty(&dev->dev_req_list)) {
                req_entry = list_entry(dev->dev_req_list.next,
                        struct gs_req_entry, re_entry);
                list_del(&req_entry->re_entry);
                gs_free_req_entry(dev->dev_in_ep, req_entry);
        }

        /* disable endpoints, forcing completion of pending i/o; */
        /* completion handlers free their requests in this case */
        if (dev->dev_notify_ep) {
                usb_ep_disable(dev->dev_notify_ep);
                dev->dev_notify_ep = NULL;
        }
        if (dev->dev_in_ep) {
                usb_ep_disable(dev->dev_in_ep);
                dev->dev_in_ep = NULL;
        }
        if (dev->dev_out_ep) {
                usb_ep_disable(dev->dev_out_ep);
                dev->dev_out_ep = NULL;
        }
}

/*
 * gs_build_config_buf
 *
 * Builds the config descriptors in the given buffer and returns the
 * length, or a negative error number.
 */
static int gs_build_config_buf(u8 *buf, struct usb_gadget *g,
        u8 type, unsigned int index, int is_otg)
{
        int len;
        int high_speed = 0;
        const struct usb_config_descriptor *config_desc;
        const struct usb_descriptor_header **function;

        if (index >= gs_device_desc.bNumConfigurations)
                return -EINVAL;

        /* other speed switches high and full speed */
        if (gadget_is_dualspeed(g)) {
                high_speed = (g->speed == USB_SPEED_HIGH);
                if (type == USB_DT_OTHER_SPEED_CONFIG)
                        high_speed = !high_speed;
        }

        if (use_acm) {
                config_desc = &gs_acm_config_desc;
                function = high_speed
                        ? gs_acm_highspeed_function
                        : gs_acm_fullspeed_function;
        } else {
                config_desc = &gs_bulk_config_desc;
                function = high_speed
                        ? gs_bulk_highspeed_function
                        : gs_bulk_fullspeed_function;
        }

        /* for now, don't advertise srp-only devices */
        if (!is_otg)
                function++;

        len = usb_gadget_config_buf(config_desc, buf, GS_MAX_DESC_LEN, function);
        if (len < 0)
                return len;

        ((struct usb_config_descriptor *)buf)->bDescriptorType = type;

        return len;
}

/*
 * gs_alloc_req
 *
 * Allocate a usb_request and its buffer.  Returns a pointer to the
 * usb_request or NULL if there is an error.
 */
static struct usb_request *
gs_alloc_req(struct usb_ep *ep, unsigned int len, gfp_t kmalloc_flags)
{
        struct usb_request *req;

        if (ep == NULL)
                return NULL;

        req = usb_ep_alloc_request(ep, kmalloc_flags);

        if (req != NULL) {
                req->length = len;
                req->buf = kmalloc(len, kmalloc_flags);
                if (req->buf == NULL) {
                        usb_ep_free_request(ep, req);
                        return NULL;
                }
        }

        return req;
}

/*
 * gs_free_req
 *
 * Free a usb_request and its buffer.
 */
static void gs_free_req(struct usb_ep *ep, struct usb_request *req)
{
        if (ep != NULL && req != NULL) {
                kfree(req->buf);
                usb_ep_free_request(ep, req);
        }
}

/*
 * gs_alloc_req_entry
 *
 * Allocates a request and its buffer, using the given
 * endpoint, buffer len, and kmalloc flags.
 */
static struct gs_req_entry *
gs_alloc_req_entry(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
{
        struct gs_req_entry     *req;

        req = kmalloc(sizeof(struct gs_req_entry), kmalloc_flags);
        if (req == NULL)
                return NULL;

        req->re_req = gs_alloc_req(ep, len, kmalloc_flags);
        if (req->re_req == NULL) {
                kfree(req);
                return NULL;
        }

        req->re_req->context = req;

        return req;
}

/*
 * gs_free_req_entry
 *
 * Frees a request and its buffer.
 */
static void gs_free_req_entry(struct usb_ep *ep, struct gs_req_entry *req)
{
        if (ep != NULL && req != NULL) {
                if (req->re_req != NULL)
                        gs_free_req(ep, req->re_req);
                kfree(req);
        }
}

/*
 * gs_alloc_ports
 *
 * Allocate all ports and set the gs_dev struct to point to them.
 * Return 0 if successful, or a negative error number.
 *
 * The device lock is normally held when calling this function.
 */
static int gs_alloc_ports(struct gs_dev *dev, gfp_t kmalloc_flags)
{
        int i;
        struct gs_port *port;

        if (dev == NULL)
                return -EIO;

        for (i=0; i<GS_NUM_PORTS; i++) {
                if ((port=kzalloc(sizeof(struct gs_port), kmalloc_flags)) == NULL)
                        return -ENOMEM;

                port->port_dev = dev;
                port->port_num = i;
                port->port_line_coding.dwDTERate = cpu_to_le32(GS_DEFAULT_DTE_RATE);
                port->port_line_coding.bCharFormat = GS_DEFAULT_CHAR_FORMAT;
                port->port_line_coding.bParityType = GS_DEFAULT_PARITY;
                port->port_line_coding.bDataBits = GS_DEFAULT_DATA_BITS;
                spin_lock_init(&port->port_lock);
                init_waitqueue_head(&port->port_write_wait);

                dev->dev_port[i] = port;
        }

        return 0;
}

/*
 * gs_free_ports
 *
 * Free all closed ports.  Open ports are disconnected by
 * freeing their write buffers, setting their device pointers
 * and the pointers to them in the device to NULL.  These
 * ports will be freed when closed.
 *
 * The device lock is normally held when calling this function.
 */
static void gs_free_ports(struct gs_dev *dev)
{
        int i;
        unsigned long flags;
        struct gs_port *port;

        if (dev == NULL)
                return;

        for (i=0; i<GS_NUM_PORTS; i++) {
                if ((port=dev->dev_port[i]) != NULL) {
                        dev->dev_port[i] = NULL;

                        spin_lock_irqsave(&port->port_lock, flags);

                        if (port->port_write_buf != NULL) {
                                gs_buf_free(port->port_write_buf);
                                port->port_write_buf = NULL;
                        }

                        if (port->port_open_count > 0 || port->port_in_use) {
                                port->port_dev = NULL;
                                wake_up_interruptible(&port->port_write_wait);
                                if (port->port_tty) {
                                        wake_up_interruptible(&port->port_tty->read_wait);
                                        wake_up_interruptible(&port->port_tty->write_wait);
                                }
                                spin_unlock_irqrestore(&port->port_lock, flags);
                        } else {
                                spin_unlock_irqrestore(&port->port_lock, flags);
                                kfree(port);
                        }

                }
        }
}

/* Circular Buffer */

/*
 * gs_buf_alloc
 *
 * Allocate a circular buffer and all associated memory.
 */
static struct gs_buf *gs_buf_alloc(unsigned int size, gfp_t kmalloc_flags)
{
        struct gs_buf *gb;

        if (size == 0)
                return NULL;

        gb = kmalloc(sizeof(struct gs_buf), kmalloc_flags);
        if (gb == NULL)
                return NULL;

        gb->buf_buf = kmalloc(size, kmalloc_flags);
        if (gb->buf_buf == NULL) {
                kfree(gb);
                return NULL;
        }

        gb->buf_size = size;
        gb->buf_get = gb->buf_put = gb->buf_buf;

        return gb;
}

/*
 * gs_buf_free
 *
 * Free the buffer and all associated memory.
 */
static void gs_buf_free(struct gs_buf *gb)
{
        if (gb) {
                kfree(gb->buf_buf);
                kfree(gb);
        }
}

/*
 * gs_buf_clear
 *
 * Clear out all data in the circular buffer.
 */
static void gs_buf_clear(struct gs_buf *gb)
{
        if (gb != NULL)
                gb->buf_get = gb->buf_put;
                /* equivalent to a get of all data available */
}

/*
 * gs_buf_data_avail
 *
 * Return the number of bytes of data available in the circular
 * buffer.
 */
static unsigned int gs_buf_data_avail(struct gs_buf *gb)
{
        if (gb != NULL)
                return (gb->buf_size + gb->buf_put - gb->buf_get) % gb->buf_size;
        else
                return 0;
}

/*
 * gs_buf_space_avail
 *
 * Return the number of bytes of space available in the circular
 * buffer.
 */
static unsigned int gs_buf_space_avail(struct gs_buf *gb)
{
        if (gb != NULL)
                return (gb->buf_size + gb->buf_get - gb->buf_put - 1) % gb->buf_size;
        else
                return 0;
}

/*
 * gs_buf_put
 *
 * Copy data data from a user buffer and put it into the circular buffer.
 * Restrict to the amount of space available.
 *
 * Return the number of bytes copied.
 */
static unsigned int
gs_buf_put(struct gs_buf *gb, const char *buf, unsigned int count)
{
        unsigned int len;

        if (gb == NULL)
                return 0;

        len  = gs_buf_space_avail(gb);
        if (count > len)
                count = len;

        if (count == 0)
                return 0;

        len = gb->buf_buf + gb->buf_size - gb->buf_put;
        if (count > len) {
                memcpy(gb->buf_put, buf, len);
                memcpy(gb->buf_buf, buf+len, count - len);
                gb->buf_put = gb->buf_buf + count - len;
        } else {
                memcpy(gb->buf_put, buf, count);
                if (count < len)
                        gb->buf_put += count;
                else /* count == len */
                        gb->buf_put = gb->buf_buf;
        }

        return count;
}

/*
 * gs_buf_get
 *
 * Get data from the circular buffer and copy to the given buffer.
 * Restrict to the amount of data available.
 *
 * Return the number of bytes copied.
 */
static unsigned int
gs_buf_get(struct gs_buf *gb, char *buf, unsigned int count)
{
        unsigned int len;

        if (gb == NULL)
                return 0;

        len = gs_buf_data_avail(gb);
        if (count > len)
                count = len;

        if (count == 0)
                return 0;

        len = gb->buf_buf + gb->buf_size - gb->buf_get;
        if (count > len) {
                memcpy(buf, gb->buf_get, len);
                memcpy(buf+len, gb->buf_buf, count - len);
                gb->buf_get = gb->buf_buf + count - len;
        } else {
                memcpy(buf, gb->buf_get, count);
                if (count < len)
                        gb->buf_get += count;
                else /* count == len */
                        gb->buf_get = gb->buf_buf;
        }

        return count;
}