/*
- * Internal header for libusb
- * Copyright (C) 2007 Daniel Drake <dsd@gentoo.org>
- * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ * Internal header for libusbx
+ * Copyright © 2007-2009 Daniel Drake <dsd@gentoo.org>
+ * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
-#ifndef __LIBUSBI_H__
-#define __LIBUSBI_H__
+#ifndef LIBUSBI_H
+#define LIBUSBI_H
#include <config.h>
-#include <endian.h>
#include <stddef.h>
-#include <sys/ioctl.h>
+#include <stdint.h>
#include <time.h>
+#include <stdarg.h>
+#ifdef HAVE_POLL_H
+#include <poll.h>
+#endif
#include <libusb.h>
-#include <usbfs.h>
+#include "version.h"
+
+/* Inside the libusbx code, mark all public functions as follows:
+ * return_type API_EXPORTED function_name(params) { ... }
+ * But if the function returns a pointer, mark it as follows:
+ * DEFAULT_VISIBILITY return_type * LIBUSB_CALL function_name(params) { ... }
+ * In the libusbx public header, mark all declarations as:
+ * return_type LIBUSB_CALL function_name(params);
+ */
+#define API_EXPORTED LIBUSB_CALL DEFAULT_VISIBILITY
-#define USBFS_PATH "/dev/bus/usb"
#define DEVICE_DESC_LENGTH 18
#define USB_MAXENDPOINTS 32
#define USB_MAXINTERFACES 32
#define USB_MAXCONFIG 8
+/* The following is used to silence warnings for unused variables */
+#define UNUSED(var) (void)(var)
+
struct list_head {
struct list_head *prev, *next;
};
-/* Get an entry from the list
- * ptr - the address of this list_head element in "type"
+/* Get an entry from the list
+ * ptr - the address of this list_head element in "type"
* type - the data type that contains "member"
- * member - the list_head element in "type"
+ * member - the list_head element in "type"
*/
#define list_entry(ptr, type, member) \
- ((type *)((char *)(ptr) - (unsigned long)(&((type *)0L)->member)))
+ ((type *)((uintptr_t)(ptr) - (uintptr_t)offsetof(type, member)))
/* Get each entry from a list
* pos - A structure pointer has a "member" element
* head - list head
* member - the list_head element in "pos"
+ * type - the type of the first parameter
*/
-#define list_for_each_entry(pos, head, member) \
- for (pos = list_entry((head)->next, typeof(*pos), member); \
- &pos->member != (head); \
- pos = list_entry(pos->member.next, typeof(*pos), member))
+#define list_for_each_entry(pos, head, member, type) \
+ for (pos = list_entry((head)->next, type, member); \
+ &pos->member != (head); \
+ pos = list_entry(pos->member.next, type, member))
-#define list_for_each_entry_safe(pos, n, head, member) \
- for (pos = list_entry((head)->next, typeof(*pos), member), \
- n = list_entry(pos->member.next, typeof(*pos), member); \
- &pos->member != (head); \
- pos = n, n = list_entry(n->member.next, typeof(*n), member))
+#define list_for_each_entry_safe(pos, n, head, member, type) \
+ for (pos = list_entry((head)->next, type, member), \
+ n = list_entry(pos->member.next, type, member); \
+ &pos->member != (head); \
+ pos = n, n = list_entry(n->member.next, type, member))
#define list_empty(entry) ((entry)->next == (entry))
{
entry->next->prev = entry->prev;
entry->prev->next = entry->next;
+ entry->next = entry->prev = NULL;
+}
+
+static inline void *usbi_reallocf(void *ptr, size_t size)
+{
+ void *ret = realloc(ptr, size);
+ if (!ret)
+ free(ptr);
+ return ret;
}
#define container_of(ptr, type, member) ({ \
- const typeof( ((type *)0)->member ) *__mptr = (ptr); \
- (type *)( (char *)__mptr - offsetof(type,member) );})
-
-#define bswap16(x) (((x & 0xff) << 8) | (x >> 8))
-#if __BYTE_ORDER == __LITTLE_ENDIAN
-#define cpu_to_le16(x) (x)
-#define le16_to_cpu(x) (x)
-#elif __BYTE_ORDER == __BIG_ENDIAN
-#define le16_to_cpu(x) bswap16(x)
-#define cpu_to_le16(x) bswap16(x)
-#else
-#error "Unrecognized endianness"
-#endif
+ const typeof( ((type *)0)->member ) *mptr = (ptr); \
+ (type *)( (char *)mptr - offsetof(type,member) );})
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define TIMESPEC_IS_SET(ts) ((ts)->tv_sec != 0 || (ts)->tv_nsec != 0)
-enum usbi_log_level {
- LOG_LEVEL_DEBUG,
- LOG_LEVEL_INFO,
- LOG_LEVEL_WARNING,
- LOG_LEVEL_ERROR,
-};
+void usbi_log(struct libusb_context *ctx, enum libusb_log_level level,
+ const char *function, const char *format, ...);
-void usbi_log(enum usbi_log_level, const char *function, const char *format, ...);
+void usbi_log_v(struct libusb_context *ctx, enum libusb_log_level level,
+ const char *function, const char *format, va_list args);
+
+#if !defined(_MSC_VER) || _MSC_VER >= 1400
#ifdef ENABLE_LOGGING
-#define _usbi_log(level, fmt...) usbi_log(level, __FUNCTION__, fmt)
+#define _usbi_log(ctx, level, ...) usbi_log(ctx, level, __FUNCTION__, __VA_ARGS__)
+#define usbi_dbg(...) _usbi_log(NULL, LIBUSB_LOG_LEVEL_DEBUG, __VA_ARGS__)
#else
-#define _usbi_log(level, fmt...)
+#define _usbi_log(ctx, level, ...) do { (void)(ctx); } while(0)
+#define usbi_dbg(...) do {} while(0)
#endif
-#ifdef ENABLE_DEBUG_LOGGING
-#define usbi_dbg(fmt...) _usbi_log(LOG_LEVEL_DEBUG, fmt)
+#define usbi_info(ctx, ...) _usbi_log(ctx, LIBUSB_LOG_LEVEL_INFO, __VA_ARGS__)
+#define usbi_warn(ctx, ...) _usbi_log(ctx, LIBUSB_LOG_LEVEL_WARNING, __VA_ARGS__)
+#define usbi_err(ctx, ...) _usbi_log(ctx, LIBUSB_LOG_LEVEL_ERROR, __VA_ARGS__)
+
+#else /* !defined(_MSC_VER) || _MSC_VER >= 1400 */
+
+#ifdef ENABLE_LOGGING
+#define LOG_BODY(ctxt, level) \
+{ \
+ va_list args; \
+ va_start (args, format); \
+ usbi_log_v(ctxt, level, "", format, args); \
+ va_end(args); \
+}
#else
-#define usbi_dbg(fmt...)
+#define LOG_BODY(ctxt, level) do { (void)(ctxt); } while(0)
+#endif
+
+static inline void usbi_info(struct libusb_context *ctx, const char *format,
+ ...)
+ LOG_BODY(ctx,LIBUSB_LOG_LEVEL_INFO)
+static inline void usbi_warn(struct libusb_context *ctx, const char *format,
+ ...)
+ LOG_BODY(ctx,LIBUSB_LOG_LEVEL_WARNING)
+static inline void usbi_err( struct libusb_context *ctx, const char *format,
+ ...)
+ LOG_BODY(ctx,LIBUSB_LOG_LEVEL_ERROR)
+
+static inline void usbi_dbg(const char *format, ...)
+ LOG_BODY(NULL,LIBUSB_LOG_LEVEL_DEBUG)
+
+#endif /* !defined(_MSC_VER) || _MSC_VER >= 1400 */
+
+#define USBI_GET_CONTEXT(ctx) if (!(ctx)) (ctx) = usbi_default_context
+#define DEVICE_CTX(dev) ((dev)->ctx)
+#define HANDLE_CTX(handle) (DEVICE_CTX((handle)->dev))
+#define TRANSFER_CTX(transfer) (HANDLE_CTX((transfer)->dev_handle))
+#define ITRANSFER_CTX(transfer) \
+ (TRANSFER_CTX(USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)))
+
+#define IS_EPIN(ep) (0 != ((ep) & LIBUSB_ENDPOINT_IN))
+#define IS_EPOUT(ep) (!IS_EPIN(ep))
+#define IS_XFERIN(xfer) (0 != ((xfer)->endpoint & LIBUSB_ENDPOINT_IN))
+#define IS_XFEROUT(xfer) (!IS_XFERIN(xfer))
+
+/* Internal abstraction for thread synchronization */
+#if defined(THREADS_POSIX)
+#include "os/threads_posix.h"
+#elif defined(OS_WINDOWS)
+#include <os/threads_windows.h>
#endif
-#define usbi_info(fmt...) _usbi_log(LOG_LEVEL_INFO, fmt)
-#define usbi_warn(fmt...) _usbi_log(LOG_LEVEL_WARNING, fmt)
-#define usbi_err(fmt...) _usbi_log(LOG_LEVEL_ERROR, fmt)
+extern struct libusb_context *usbi_default_context;
+
+struct libusb_context {
+ int debug;
+ int debug_fixed;
+
+ /* internal control pipe, used for interrupting event handling when
+ * something needs to modify poll fds. */
+ int ctrl_pipe[2];
+
+ struct list_head usb_devs;
+ usbi_mutex_t usb_devs_lock;
+
+ /* A list of open handles. Backends are free to traverse this if required.
+ */
+ struct list_head open_devs;
+ usbi_mutex_t open_devs_lock;
+
+ /* this is a list of in-flight transfer handles, sorted by timeout
+ * expiration. URBs to timeout the soonest are placed at the beginning of
+ * the list, URBs that will time out later are placed after, and urbs with
+ * infinite timeout are always placed at the very end. */
+ struct list_head flying_transfers;
+ usbi_mutex_t flying_transfers_lock;
+
+ /* list of poll fds */
+ struct list_head pollfds;
+ usbi_mutex_t pollfds_lock;
+
+ /* a counter that is set when we want to interrupt event handling, in order
+ * to modify the poll fd set. and a lock to protect it. */
+ unsigned int pollfd_modify;
+ usbi_mutex_t pollfd_modify_lock;
+
+ /* user callbacks for pollfd changes */
+ libusb_pollfd_added_cb fd_added_cb;
+ libusb_pollfd_removed_cb fd_removed_cb;
+ void *fd_cb_user_data;
+
+ /* ensures that only one thread is handling events at any one time */
+ usbi_mutex_t events_lock;
+
+ /* used to see if there is an active thread doing event handling */
+ int event_handler_active;
+
+ /* used to wait for event completion in threads other than the one that is
+ * event handling */
+ usbi_mutex_t event_waiters_lock;
+ usbi_cond_t event_waiters_cond;
+
+#ifdef USBI_TIMERFD_AVAILABLE
+ /* used for timeout handling, if supported by OS.
+ * this timerfd is maintained to trigger on the next pending timeout */
+ int timerfd;
+#endif
+};
+
+#ifdef USBI_TIMERFD_AVAILABLE
+#define usbi_using_timerfd(ctx) ((ctx)->timerfd >= 0)
+#else
+#define usbi_using_timerfd(ctx) (0)
+#endif
+
+struct libusb_device {
+ /* lock protects refcnt, everything else is finalized at initialization
+ * time */
+ usbi_mutex_t lock;
+ int refcnt;
+
+ struct libusb_context *ctx;
+
+ uint8_t bus_number;
+ uint8_t port_number;
+ struct libusb_device* parent_dev;
+ uint8_t device_address;
+ uint8_t num_configurations;
+ enum libusb_speed speed;
-struct libusb_dev {
struct list_head list;
- char *nodepath;
- struct libusb_dev_descriptor desc;
- struct libusb_config_descriptor *config;
+ unsigned long session_data;
+ unsigned char os_priv[0];
};
-struct libusb_dev_handle {
+struct libusb_device_handle {
+ /* lock protects claimed_interfaces */
+ usbi_mutex_t lock;
+ unsigned long claimed_interfaces;
+
struct list_head list;
- struct libusb_dev *dev;
- int fd;
+ struct libusb_device *dev;
+ unsigned char os_priv[0];
};
-enum libusb_urb_type {
- LIBUSB_URB_CONTROL,
- LIBUSB_URB_BULK,
+enum {
+ USBI_CLOCK_MONOTONIC,
+ USBI_CLOCK_REALTIME
};
-#define LIBUSB_URBH_DATA_BELONGS_TO_USER (1<<0)
-#define LIBUSB_URBH_SYNC_CANCELLED (1<<1)
-#define LIBUSB_URBH_TIMED_OUT (1<<2)
+/* in-memory transfer layout:
+ *
+ * 1. struct usbi_transfer
+ * 2. struct libusb_transfer (which includes iso packets) [variable size]
+ * 3. os private data [variable size]
+ *
+ * from a libusb_transfer, you can get the usbi_transfer by rewinding the
+ * appropriate number of bytes.
+ * the usbi_transfer includes the number of allocated packets, so you can
+ * determine the size of the transfer and hence the start and length of the
+ * OS-private data.
+ */
-struct libusb_urb_handle {
- struct libusb_dev_handle *devh;
- struct usb_urb urb;
+struct usbi_transfer {
+ int num_iso_packets;
struct list_head list;
- struct timespec timeout;
- timer_t timer;
- unsigned char urb_type;
- unsigned char endpoint;
- int transfer_len;
+ struct timeval timeout;
int transferred;
- unsigned char *buffer;
- void *callback;
- void *user_data;
uint8_t flags;
+
+ /* this lock is held during libusb_submit_transfer() and
+ * libusb_cancel_transfer() (allowing the OS backend to prevent duplicate
+ * cancellation, submission-during-cancellation, etc). the OS backend
+ * should also take this lock in the handle_events path, to prevent the user
+ * cancelling the transfer from another thread while you are processing
+ * its completion (presumably there would be races within your OS backend
+ * if this were possible). */
+ usbi_mutex_t lock;
};
+enum usbi_transfer_flags {
+ /* The transfer has timed out */
+ USBI_TRANSFER_TIMED_OUT = 1 << 0,
+
+ /* Set by backend submit_transfer() if the OS handles timeout */
+ USBI_TRANSFER_OS_HANDLES_TIMEOUT = 1 << 1,
+
+ /* Cancellation was requested via libusb_cancel_transfer() */
+ USBI_TRANSFER_CANCELLING = 1 << 2,
+
+ /* Operation on the transfer failed because the device disappeared */
+ USBI_TRANSFER_DEVICE_DISAPPEARED = 1 << 3,
+
+ /* Set by backend submit_transfer() if the fds in use have been updated */
+ USBI_TRANSFER_UPDATED_FDS = 1 << 4,
+};
+
+#define USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer) \
+ ((struct libusb_transfer *)(((unsigned char *)(transfer)) \
+ + sizeof(struct usbi_transfer)))
+#define LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer) \
+ ((struct usbi_transfer *)(((unsigned char *)(transfer)) \
+ - sizeof(struct usbi_transfer)))
+
+static inline void *usbi_transfer_get_os_priv(struct usbi_transfer *transfer)
+{
+ return ((unsigned char *)transfer) + sizeof(struct usbi_transfer)
+ + sizeof(struct libusb_transfer)
+ + (transfer->num_iso_packets
+ * sizeof(struct libusb_iso_packet_descriptor));
+}
+
/* bus structures */
/* All standard descriptors have these 2 fields in common */
/* shared data and functions */
-extern struct list_head open_devs;
+int usbi_io_init(struct libusb_context *ctx);
+void usbi_io_exit(struct libusb_context *ctx);
+
+struct libusb_device *usbi_alloc_device(struct libusb_context *ctx,
+ unsigned long session_id);
+struct libusb_device *usbi_get_device_by_session_id(struct libusb_context *ctx,
+ unsigned long session_id);
+int usbi_sanitize_device(struct libusb_device *dev);
+void usbi_handle_disconnect(struct libusb_device_handle *handle);
+
+int usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
+ enum libusb_transfer_status status);
+int usbi_handle_transfer_cancellation(struct usbi_transfer *transfer);
+
+int usbi_parse_descriptor(unsigned char *source, const char *descriptor,
+ void *dest, int host_endian);
+int usbi_get_config_index_by_value(struct libusb_device *dev,
+ uint8_t bConfigurationValue, int *idx);
+
+/* Internal abstraction for poll (needs struct usbi_transfer on Windows) */
+#if defined(OS_LINUX) || defined(OS_DARWIN) || defined(OS_OPENBSD)
+#include <unistd.h>
+#include "os/poll_posix.h"
+#elif defined(OS_WINDOWS) || defined(OS_WINCE)
+#include <os/poll_windows.h>
+#endif
+
+#if defined(OS_WINDOWS) && !defined(__GCC__)
+#undef HAVE_GETTIMEOFDAY
+int usbi_gettimeofday(struct timeval *tp, void *tzp);
+#define LIBUSB_GETTIMEOFDAY_WIN32
+#define HAVE_USBI_GETTIMEOFDAY
+#else
+#ifdef HAVE_GETTIMEOFDAY
+#define usbi_gettimeofday(tv, tz) gettimeofday((tv), (tz))
+#define HAVE_USBI_GETTIMEOFDAY
+#endif
+#endif
+
+struct usbi_pollfd {
+ /* must come first */
+ struct libusb_pollfd pollfd;
-int usbi_io_init(int _signum);
-void usbi_io_exit(void);
+ struct list_head list;
+};
-int usbi_parse_descriptor(unsigned char *source, char *descriptor, void *dest);
-int usbi_parse_configuration(struct libusb_config_descriptor *config,
- unsigned char *buffer);
+int usbi_add_pollfd(struct libusb_context *ctx, int fd, short events);
+void usbi_remove_pollfd(struct libusb_context *ctx, int fd);
+void usbi_fd_notification(struct libusb_context *ctx);
+
+/* device discovery */
+
+/* we traverse usbfs without knowing how many devices we are going to find.
+ * so we create this discovered_devs model which is similar to a linked-list
+ * which grows when required. it can be freed once discovery has completed,
+ * eliminating the need for a list node in the libusb_device structure
+ * itself. */
+struct discovered_devs {
+ size_t len;
+ size_t capacity;
+ struct libusb_device *devices[0];
+};
+struct discovered_devs *discovered_devs_append(
+ struct discovered_devs *discdevs, struct libusb_device *dev);
+
+/* OS abstraction */
+
+/* This is the interface that OS backends need to implement.
+ * All fields are mandatory, except ones explicitly noted as optional. */
+struct usbi_os_backend {
+ /* A human-readable name for your backend, e.g. "Linux usbfs" */
+ const char *name;
+
+ /* Perform initialization of your backend. You might use this function
+ * to determine specific capabilities of the system, allocate required
+ * data structures for later, etc.
+ *
+ * This function is called when a libusbx user initializes the library
+ * prior to use.
+ *
+ * Return 0 on success, or a LIBUSB_ERROR code on failure.
+ */
+ int (*init)(struct libusb_context *ctx);
+
+ /* Deinitialization. Optional. This function should destroy anything
+ * that was set up by init.
+ *
+ * This function is called when the user deinitializes the library.
+ */
+ void (*exit)(void);
+
+ /* Enumerate all the USB devices on the system, returning them in a list
+ * of discovered devices.
+ *
+ * Your implementation should enumerate all devices on the system,
+ * regardless of whether they have been seen before or not.
+ *
+ * When you have found a device, compute a session ID for it. The session
+ * ID should uniquely represent that particular device for that particular
+ * connection session since boot (i.e. if you disconnect and reconnect a
+ * device immediately after, it should be assigned a different session ID).
+ * If your OS cannot provide a unique session ID as described above,
+ * presenting a session ID of (bus_number << 8 | device_address) should
+ * be sufficient. Bus numbers and device addresses wrap and get reused,
+ * but that is an unlikely case.
+ *
+ * After computing a session ID for a device, call
+ * usbi_get_device_by_session_id(). This function checks if libusbx already
+ * knows about the device, and if so, it provides you with a libusb_device
+ * structure for it.
+ *
+ * If usbi_get_device_by_session_id() returns NULL, it is time to allocate
+ * a new device structure for the device. Call usbi_alloc_device() to
+ * obtain a new libusb_device structure with reference count 1. Populate
+ * the bus_number and device_address attributes of the new device, and
+ * perform any other internal backend initialization you need to do. At
+ * this point, you should be ready to provide device descriptors and so
+ * on through the get_*_descriptor functions. Finally, call
+ * usbi_sanitize_device() to perform some final sanity checks on the
+ * device. Assuming all of the above succeeded, we can now continue.
+ * If any of the above failed, remember to unreference the device that
+ * was returned by usbi_alloc_device().
+ *
+ * At this stage we have a populated libusb_device structure (either one
+ * that was found earlier, or one that we have just allocated and
+ * populated). This can now be added to the discovered devices list
+ * using discovered_devs_append(). Note that discovered_devs_append()
+ * may reallocate the list, returning a new location for it, and also
+ * note that reallocation can fail. Your backend should handle these
+ * error conditions appropriately.
+ *
+ * This function should not generate any bus I/O and should not block.
+ * If I/O is required (e.g. reading the active configuration value), it is
+ * OK to ignore these suggestions :)
+ *
+ * This function is executed when the user wishes to retrieve a list
+ * of USB devices connected to the system.
+ *
+ * Return 0 on success, or a LIBUSB_ERROR code on failure.
+ */
+ int (*get_device_list)(struct libusb_context *ctx,
+ struct discovered_devs **discdevs);
+
+ /* Open a device for I/O and other USB operations. The device handle
+ * is preallocated for you, you can retrieve the device in question
+ * through handle->dev.
+ *
+ * Your backend should allocate any internal resources required for I/O
+ * and other operations so that those operations can happen (hopefully)
+ * without hiccup. This is also a good place to inform libusbx that it
+ * should monitor certain file descriptors related to this device -
+ * see the usbi_add_pollfd() function.
+ *
+ * This function should not generate any bus I/O and should not block.
+ *
+ * This function is called when the user attempts to obtain a device
+ * handle for a device.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_ACCESS if the user has insufficient permissions
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since
+ * discovery
+ * - another LIBUSB_ERROR code on other failure
+ *
+ * Do not worry about freeing the handle on failed open, the upper layers
+ * do this for you.
+ */
+ int (*open)(struct libusb_device_handle *handle);
+
+ /* Close a device such that the handle cannot be used again. Your backend
+ * should destroy any resources that were allocated in the open path.
+ * This may also be a good place to call usbi_remove_pollfd() to inform
+ * libusbx of any file descriptors associated with this device that should
+ * no longer be monitored.
+ *
+ * This function is called when the user closes a device handle.
+ */
+ void (*close)(struct libusb_device_handle *handle);
+
+ /* Retrieve the device descriptor from a device.
+ *
+ * The descriptor should be retrieved from memory, NOT via bus I/O to the
+ * device. This means that you may have to cache it in a private structure
+ * during get_device_list enumeration. Alternatively, you may be able
+ * to retrieve it from a kernel interface (some Linux setups can do this)
+ * still without generating bus I/O.
+ *
+ * This function is expected to write DEVICE_DESC_LENGTH (18) bytes into
+ * buffer, which is guaranteed to be big enough.
+ *
+ * This function is called when sanity-checking a device before adding
+ * it to the list of discovered devices, and also when the user requests
+ * to read the device descriptor.
+ *
+ * This function is expected to return the descriptor in bus-endian format
+ * (LE). If it returns the multi-byte values in host-endian format,
+ * set the host_endian output parameter to "1".
+ *
+ * Return 0 on success or a LIBUSB_ERROR code on failure.
+ */
+ int (*get_device_descriptor)(struct libusb_device *device,
+ unsigned char *buffer, int *host_endian);
+
+ /* Get the ACTIVE configuration descriptor for a device.
+ *
+ * The descriptor should be retrieved from memory, NOT via bus I/O to the
+ * device. This means that you may have to cache it in a private structure
+ * during get_device_list enumeration. You may also have to keep track
+ * of which configuration is active when the user changes it.
+ *
+ * This function is expected to write len bytes of data into buffer, which
+ * is guaranteed to be big enough. If you can only do a partial write,
+ * return an error code.
+ *
+ * This function is expected to return the descriptor in bus-endian format
+ * (LE). If it returns the multi-byte values in host-endian format,
+ * set the host_endian output parameter to "1".
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NOT_FOUND if the device is in unconfigured state
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*get_active_config_descriptor)(struct libusb_device *device,
+ unsigned char *buffer, size_t len, int *host_endian);
+
+ /* Get a specific configuration descriptor for a device.
+ *
+ * The descriptor should be retrieved from memory, NOT via bus I/O to the
+ * device. This means that you may have to cache it in a private structure
+ * during get_device_list enumeration.
+ *
+ * The requested descriptor is expressed as a zero-based index (i.e. 0
+ * indicates that we are requesting the first descriptor). The index does
+ * not (necessarily) equal the bConfigurationValue of the configuration
+ * being requested.
+ *
+ * This function is expected to write len bytes of data into buffer, which
+ * is guaranteed to be big enough. If you can only do a partial write,
+ * return an error code.
+ *
+ * This function is expected to return the descriptor in bus-endian format
+ * (LE). If it returns the multi-byte values in host-endian format,
+ * set the host_endian output parameter to "1".
+ *
+ * Return 0 on success or a LIBUSB_ERROR code on failure.
+ */
+ int (*get_config_descriptor)(struct libusb_device *device,
+ uint8_t config_index, unsigned char *buffer, size_t len,
+ int *host_endian);
+
+ /* Get the bConfigurationValue for the active configuration for a device.
+ * Optional. This should only be implemented if you can retrieve it from
+ * cache (don't generate I/O).
+ *
+ * If you cannot retrieve this from cache, either do not implement this
+ * function, or return LIBUSB_ERROR_NOT_SUPPORTED. This will cause
+ * libusbx to retrieve the information through a standard control transfer.
+ *
+ * This function must be non-blocking.
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+ * was opened
+ * - LIBUSB_ERROR_NOT_SUPPORTED if the value cannot be retrieved without
+ * blocking
+ * - another LIBUSB_ERROR code on other failure.
+ */
+ int (*get_configuration)(struct libusb_device_handle *handle, int *config);
+
+ /* Set the active configuration for a device.
+ *
+ * A configuration value of -1 should put the device in unconfigured state.
+ *
+ * This function can block.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
+ * - LIBUSB_ERROR_BUSY if interfaces are currently claimed (and hence
+ * configuration cannot be changed)
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+ * was opened
+ * - another LIBUSB_ERROR code on other failure.
+ */
+ int (*set_configuration)(struct libusb_device_handle *handle, int config);
+
+ /* Claim an interface. When claimed, the application can then perform
+ * I/O to an interface's endpoints.
+ *
+ * This function should not generate any bus I/O and should not block.
+ * Interface claiming is a logical operation that simply ensures that
+ * no other drivers/applications are using the interface, and after
+ * claiming, no other drivers/applicatiosn can use the interface because
+ * we now "own" it.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NOT_FOUND if the interface does not exist
+ * - LIBUSB_ERROR_BUSY if the interface is in use by another driver/app
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+ * was opened
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*claim_interface)(struct libusb_device_handle *handle, int interface_number);
+
+ /* Release a previously claimed interface.
+ *
+ * This function should also generate a SET_INTERFACE control request,
+ * resetting the alternate setting of that interface to 0. It's OK for
+ * this function to block as a result.
+ *
+ * You will only ever be asked to release an interface which was
+ * successfully claimed earlier.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+ * was opened
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*release_interface)(struct libusb_device_handle *handle, int interface_number);
+
+ /* Set the alternate setting for an interface.
+ *
+ * You will only ever be asked to set the alternate setting for an
+ * interface which was successfully claimed earlier.
+ *
+ * It's OK for this function to block.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NOT_FOUND if the alternate setting does not exist
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+ * was opened
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*set_interface_altsetting)(struct libusb_device_handle *handle,
+ int interface_number, int altsetting);
+
+ /* Clear a halt/stall condition on an endpoint.
+ *
+ * It's OK for this function to block.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+ * was opened
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*clear_halt)(struct libusb_device_handle *handle,
+ unsigned char endpoint);
+
+ /* Perform a USB port reset to reinitialize a device.
+ *
+ * If possible, the handle should still be usable after the reset
+ * completes, assuming that the device descriptors did not change during
+ * reset and all previous interface state can be restored.
+ *
+ * If something changes, or you cannot easily locate/verify the resetted
+ * device, return LIBUSB_ERROR_NOT_FOUND. This prompts the application
+ * to close the old handle and re-enumerate the device.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NOT_FOUND if re-enumeration is required, or if the device
+ * has been disconnected since it was opened
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*reset_device)(struct libusb_device_handle *handle);
+
+ /* Determine if a kernel driver is active on an interface. Optional.
+ *
+ * The presence of a kernel driver on an interface indicates that any
+ * calls to claim_interface would fail with the LIBUSB_ERROR_BUSY code.
+ *
+ * Return:
+ * - 0 if no driver is active
+ * - 1 if a driver is active
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+ * was opened
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*kernel_driver_active)(struct libusb_device_handle *handle,
+ int interface_number);
+
+ /* Detach a kernel driver from an interface. Optional.
+ *
+ * After detaching a kernel driver, the interface should be available
+ * for claim.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
+ * - LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+ * was opened
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*detach_kernel_driver)(struct libusb_device_handle *handle,
+ int interface_number);
+
+ /* Attach a kernel driver to an interface. Optional.
+ *
+ * Reattach a kernel driver to the device.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
+ * - LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+ * was opened
+ * - LIBUSB_ERROR_BUSY if a program or driver has claimed the interface,
+ * preventing reattachment
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*attach_kernel_driver)(struct libusb_device_handle *handle,
+ int interface_number);
+
+ /* Destroy a device. Optional.
+ *
+ * This function is called when the last reference to a device is
+ * destroyed. It should free any resources allocated in the get_device_list
+ * path.
+ */
+ void (*destroy_device)(struct libusb_device *dev);
+
+ /* Submit a transfer. Your implementation should take the transfer,
+ * morph it into whatever form your platform requires, and submit it
+ * asynchronously.
+ *
+ * This function must not block.
+ *
+ * Return:
+ * - 0 on success
+ * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * - another LIBUSB_ERROR code on other failure
+ */
+ int (*submit_transfer)(struct usbi_transfer *itransfer);
+
+ /* Cancel a previously submitted transfer.
+ *
+ * This function must not block. The transfer cancellation must complete
+ * later, resulting in a call to usbi_handle_transfer_cancellation()
+ * from the context of handle_events.
+ */
+ int (*cancel_transfer)(struct usbi_transfer *itransfer);
+
+ /* Clear a transfer as if it has completed or cancelled, but do not
+ * report any completion/cancellation to the library. You should free
+ * all private data from the transfer as if you were just about to report
+ * completion or cancellation.
+ *
+ * This function might seem a bit out of place. It is used when libusbx
+ * detects a disconnected device - it calls this function for all pending
+ * transfers before reporting completion (with the disconnect code) to
+ * the user. Maybe we can improve upon this internal interface in future.
+ */
+ void (*clear_transfer_priv)(struct usbi_transfer *itransfer);
+
+ /* Handle any pending events. This involves monitoring any active
+ * transfers and processing their completion or cancellation.
+ *
+ * The function is passed an array of pollfd structures (size nfds)
+ * as a result of the poll() system call. The num_ready parameter
+ * indicates the number of file descriptors that have reported events
+ * (i.e. the poll() return value). This should be enough information
+ * for you to determine which actions need to be taken on the currently
+ * active transfers.
+ *
+ * For any cancelled transfers, call usbi_handle_transfer_cancellation().
+ * For completed transfers, call usbi_handle_transfer_completion().
+ * For control/bulk/interrupt transfers, populate the "transferred"
+ * element of the appropriate usbi_transfer structure before calling the
+ * above functions. For isochronous transfers, populate the status and
+ * transferred fields of the iso packet descriptors of the transfer.
+ *
+ * This function should also be able to detect disconnection of the
+ * device, reporting that situation with usbi_handle_disconnect().
+ *
+ * When processing an event related to a transfer, you probably want to
+ * take usbi_transfer.lock to prevent races. See the documentation for
+ * the usbi_transfer structure.
+ *
+ * Return 0 on success, or a LIBUSB_ERROR code on failure.
+ */
+ int (*handle_events)(struct libusb_context *ctx,
+ struct pollfd *fds, POLL_NFDS_TYPE nfds, int num_ready);
+
+ /* Get time from specified clock. At least two clocks must be implemented
+ by the backend: USBI_CLOCK_REALTIME, and USBI_CLOCK_MONOTONIC.
+
+ Description of clocks:
+ USBI_CLOCK_REALTIME : clock returns time since system epoch.
+ USBI_CLOCK_MONOTONIC: clock returns time since unspecified start
+ time (usually boot).
+ */
+ int (*clock_gettime)(int clkid, struct timespec *tp);
+
+#ifdef USBI_TIMERFD_AVAILABLE
+ /* clock ID of the clock that should be used for timerfd */
+ clockid_t (*get_timerfd_clockid)(void);
#endif
+ /* Number of bytes to reserve for per-device private backend data.
+ * This private data area is accessible through the "os_priv" field of
+ * struct libusb_device. */
+ size_t device_priv_size;
+
+ /* Number of bytes to reserve for per-handle private backend data.
+ * This private data area is accessible through the "os_priv" field of
+ * struct libusb_device. */
+ size_t device_handle_priv_size;
+
+ /* Number of bytes to reserve for per-transfer private backend data.
+ * This private data area is accessible by calling
+ * usbi_transfer_get_os_priv() on the appropriate usbi_transfer instance.
+ */
+ size_t transfer_priv_size;
+
+ /* Mumber of additional bytes for os_priv for each iso packet.
+ * Can your backend use this? */
+ /* FIXME: linux can't use this any more. if other OS's cannot either,
+ * then remove this */
+ size_t add_iso_packet_size;
+};
+
+extern const struct usbi_os_backend * const usbi_backend;
+
+extern const struct usbi_os_backend linux_usbfs_backend;
+extern const struct usbi_os_backend darwin_backend;
+extern const struct usbi_os_backend openbsd_backend;
+extern const struct usbi_os_backend windows_backend;
+
+#endif