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serial.c

/*
 * 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;
}

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