2 * Internal header for libusb
3 * Copyright (C) 2007-2009 Daniel Drake <dsd@gentoo.org>
4 * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
32 #define DEVICE_DESC_LENGTH 18
34 #define USB_MAXENDPOINTS 32
35 #define USB_MAXINTERFACES 32
36 #define USB_MAXCONFIG 8
39 struct list_head *prev, *next;
42 /* Get an entry from the list
43 * ptr - the address of this list_head element in "type"
44 * type - the data type that contains "member"
45 * member - the list_head element in "type"
47 #define list_entry(ptr, type, member) \
48 ((type *)((char *)(ptr) - (unsigned long)(&((type *)0L)->member)))
50 /* Get each entry from a list
51 * pos - A structure pointer has a "member" element
53 * member - the list_head element in "pos"
54 * type - the type of the first parameter
56 #define list_for_each_entry(pos, head, member, type) \
57 for (pos = list_entry((head)->next, type, member); \
58 &pos->member != (head); \
59 pos = list_entry(pos->member.next, type, member))
61 #define list_for_each_entry_safe(pos, n, head, member, type) \
62 for (pos = list_entry((head)->next, type, member), \
63 n = list_entry(pos->member.next, type, member); \
64 &pos->member != (head); \
65 pos = n, n = list_entry(n->member.next, type, member))
67 #define list_empty(entry) ((entry)->next == (entry))
69 static inline void list_init(struct list_head *entry)
71 entry->prev = entry->next = entry;
74 static inline void list_add(struct list_head *entry, struct list_head *head)
76 entry->next = head->next;
79 head->next->prev = entry;
83 static inline void list_add_tail(struct list_head *entry,
84 struct list_head *head)
87 entry->prev = head->prev;
89 head->prev->next = entry;
93 static inline void list_del(struct list_head *entry)
95 entry->next->prev = entry->prev;
96 entry->prev->next = entry->next;
99 #define container_of(ptr, type, member) ({ \
100 const typeof( ((type *)0)->member ) *__mptr = (ptr); \
101 (type *)( (char *)__mptr - offsetof(type,member) );})
103 #define MIN(a, b) ((a) < (b) ? (a) : (b))
104 #define MAX(a, b) ((a) > (b) ? (a) : (b))
106 #define TIMESPEC_IS_SET(ts) ((ts)->tv_sec != 0 || (ts)->tv_nsec != 0)
108 enum usbi_log_level {
115 void usbi_log(struct libusb_context *ctx, enum usbi_log_level,
116 const char *function, const char *format, ...);
118 #ifdef ENABLE_LOGGING
119 #define _usbi_log(ctx, level, fmt...) usbi_log(ctx, level, __FUNCTION__, fmt)
121 #define _usbi_log(ctx, level, fmt...)
124 #ifdef ENABLE_DEBUG_LOGGING
125 #define usbi_dbg(fmt...) _usbi_log(NULL, LOG_LEVEL_DEBUG, fmt)
127 #define usbi_dbg(fmt...)
130 #define usbi_info(ctx, fmt...) _usbi_log(ctx, LOG_LEVEL_INFO, fmt)
131 #define usbi_warn(ctx, fmt...) _usbi_log(ctx, LOG_LEVEL_WARNING, fmt)
132 #define usbi_err(ctx, fmt...) _usbi_log(ctx, LOG_LEVEL_ERROR, fmt)
134 #define USBI_GET_CONTEXT(ctx) if (!(ctx)) (ctx) = usbi_default_context
135 #define DEVICE_CTX(dev) ((dev)->ctx)
136 #define HANDLE_CTX(handle) (DEVICE_CTX((handle)->dev))
137 #define TRANSFER_CTX(transfer) (HANDLE_CTX((transfer)->dev_handle))
138 #define ITRANSFER_CTX(transfer) \
139 (TRANSFER_CTX(__USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)))
141 /* Internal abstraction for thread synchronization */
142 #if defined(OS_LINUX) || defined(OS_DARWIN)
143 #include <os/threads_posix.h>
146 extern struct libusb_context *usbi_default_context;
148 struct libusb_context {
152 /* internal control pipe, used for interrupting event handling when
153 * something needs to modify poll fds. */
156 struct list_head usb_devs;
157 usbi_mutex_t usb_devs_lock;
159 /* A list of open handles. Backends are free to traverse this if required.
161 struct list_head open_devs;
162 usbi_mutex_t open_devs_lock;
164 /* this is a list of in-flight transfer handles, sorted by timeout
165 * expiration. URBs to timeout the soonest are placed at the beginning of
166 * the list, URBs that will time out later are placed after, and urbs with
167 * infinite timeout are always placed at the very end. */
168 struct list_head flying_transfers;
169 usbi_mutex_t flying_transfers_lock;
171 /* list of poll fds */
172 struct list_head pollfds;
173 usbi_mutex_t pollfds_lock;
175 /* a counter that is set when we want to interrupt event handling, in order
176 * to modify the poll fd set. and a lock to protect it. */
177 unsigned int pollfd_modify;
178 usbi_mutex_t pollfd_modify_lock;
180 /* user callbacks for pollfd changes */
181 libusb_pollfd_added_cb fd_added_cb;
182 libusb_pollfd_removed_cb fd_removed_cb;
183 void *fd_cb_user_data;
185 /* ensures that only one thread is handling events at any one time */
186 usbi_mutex_t events_lock;
188 /* used to see if there is an active thread doing event handling */
189 int event_handler_active;
191 /* used to wait for event completion in threads other than the one that is
193 usbi_mutex_t event_waiters_lock;
194 usbi_cond_t event_waiters_cond;
196 #ifdef USBI_TIMERFD_AVAILABLE
197 /* used for timeout handling, if supported by OS.
198 * this timerfd is maintained to trigger on the next pending timeout */
203 #ifdef USBI_TIMERFD_AVAILABLE
204 #define usbi_using_timerfd(ctx) ((ctx)->timerfd >= 0)
206 #define usbi_using_timerfd(ctx) (0)
209 struct libusb_device {
210 /* lock protects refcnt, everything else is finalized at initialization
215 struct libusb_context *ctx;
218 uint8_t device_address;
219 uint8_t num_configurations;
221 struct list_head list;
222 unsigned long session_data;
223 unsigned char os_priv[0];
226 struct libusb_device_handle {
227 /* lock protects claimed_interfaces */
229 unsigned long claimed_interfaces;
231 struct list_head list;
232 struct libusb_device *dev;
233 unsigned char os_priv[0];
236 #define USBI_TRANSFER_TIMED_OUT (1<<0)
239 USBI_CLOCK_MONOTONIC,
243 /* in-memory transfer layout:
245 * 1. struct usbi_transfer
246 * 2. struct libusb_transfer (which includes iso packets) [variable size]
247 * 3. os private data [variable size]
249 * from a libusb_transfer, you can get the usbi_transfer by rewinding the
250 * appropriate number of bytes.
251 * the usbi_transfer includes the number of allocated packets, so you can
252 * determine the size of the transfer and hence the start and length of the
256 struct usbi_transfer {
258 struct list_head list;
259 struct timeval timeout;
263 /* this lock is held during libusb_submit_transfer() and
264 * libusb_cancel_transfer() (allowing the OS backend to prevent duplicate
265 * cancellation, submission-during-cancellation, etc). the OS backend
266 * should also take this lock in the handle_events path, to prevent the user
267 * cancelling the transfer from another thread while you are processing
268 * its completion (presumably there would be races within your OS backend
269 * if this were possible). */
273 #define __USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer) \
274 ((struct libusb_transfer *)(((unsigned char *)(transfer)) \
275 + sizeof(struct usbi_transfer)))
276 #define __LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer) \
277 ((struct usbi_transfer *)(((unsigned char *)(transfer)) \
278 - sizeof(struct usbi_transfer)))
280 static inline void *usbi_transfer_get_os_priv(struct usbi_transfer *transfer)
282 return ((unsigned char *)transfer) + sizeof(struct usbi_transfer)
283 + sizeof(struct libusb_transfer)
284 + (transfer->num_iso_packets
285 * sizeof(struct libusb_iso_packet_descriptor));
290 /* All standard descriptors have these 2 fields in common */
291 struct usb_descriptor_header {
293 uint8_t bDescriptorType;
296 /* shared data and functions */
298 int usbi_io_init(struct libusb_context *ctx);
299 void usbi_io_exit(struct libusb_context *ctx);
301 struct libusb_device *usbi_alloc_device(struct libusb_context *ctx,
302 unsigned long session_id);
303 struct libusb_device *usbi_get_device_by_session_id(struct libusb_context *ctx,
304 unsigned long session_id);
305 int usbi_sanitize_device(struct libusb_device *dev);
306 void usbi_handle_disconnect(struct libusb_device_handle *handle);
308 int usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
309 enum libusb_transfer_status status);
310 int usbi_handle_transfer_cancellation(struct usbi_transfer *transfer);
312 int usbi_parse_descriptor(unsigned char *source, char *descriptor, void *dest,
314 int usbi_get_config_index_by_value(struct libusb_device *dev,
315 uint8_t bConfigurationValue, int *idx);
320 /* must come first */
321 struct libusb_pollfd pollfd;
323 struct list_head list;
326 int usbi_add_pollfd(struct libusb_context *ctx, int fd, short events);
327 void usbi_remove_pollfd(struct libusb_context *ctx, int fd);
329 /* device discovery */
331 /* we traverse usbfs without knowing how many devices we are going to find.
332 * so we create this discovered_devs model which is similar to a linked-list
333 * which grows when required. it can be freed once discovery has completed,
334 * eliminating the need for a list node in the libusb_device structure
336 struct discovered_devs {
339 struct libusb_device *devices[0];
342 struct discovered_devs *discovered_devs_append(
343 struct discovered_devs *discdevs, struct libusb_device *dev);
347 /* This is the interface that OS backends need to implement.
348 * All fields are mandatory, except ones explicitly noted as optional. */
349 struct usbi_os_backend {
350 /* A human-readable name for your backend, e.g. "Linux usbfs" */
353 /* Perform initialization of your backend. You might use this function
354 * to determine specific capabilities of the system, allocate required
355 * data structures for later, etc.
357 * This function is called when a libusb user initializes the library
360 * Return 0 on success, or a LIBUSB_ERROR code on failure.
362 int (*init)(struct libusb_context *ctx);
364 /* Deinitialization. Optional. This function should destroy anything
365 * that was set up by init.
367 * This function is called when the user deinitializes the library.
371 /* Enumerate all the USB devices on the system, returning them in a list
372 * of discovered devices.
374 * Your implementation should enumerate all devices on the system,
375 * regardless of whether they have been seen before or not.
377 * When you have found a device, compute a session ID for it. The session
378 * ID should uniquely represent that particular device for that particular
379 * connection session since boot (i.e. if you disconnect and reconnect a
380 * device immediately after, it should be assigned a different session ID).
381 * If your OS cannot provide a unique session ID as described above,
382 * presenting a session ID of (bus_number << 8 | device_address) should
383 * be sufficient. Bus numbers and device addresses wrap and get reused,
384 * but that is an unlikely case.
386 * After computing a session ID for a device, call
387 * usbi_get_device_by_session_id(). This function checks if libusb already
388 * knows about the device, and if so, it provides you with a libusb_device
391 * If usbi_get_device_by_session_id() returns NULL, it is time to allocate
392 * a new device structure for the device. Call usbi_alloc_device() to
393 * obtain a new libusb_device structure with reference count 1. Populate
394 * the bus_number and device_address attributes of the new device, and
395 * perform any other internal backend initialization you need to do. At
396 * this point, you should be ready to provide device descriptors and so
397 * on through the get_*_descriptor functions. Finally, call
398 * usbi_sanitize_device() to perform some final sanity checks on the
399 * device. Assuming all of the above succeeded, we can now continue.
400 * If any of the above failed, remember to unreference the device that
401 * was returned by usbi_alloc_device().
403 * At this stage we have a populated libusb_device structure (either one
404 * that was found earlier, or one that we have just allocated and
405 * populated). This can now be added to the discovered devices list
406 * using discovered_devs_append(). Note that discovered_devs_append()
407 * may reallocate the list, returning a new location for it, and also
408 * note that reallocation can fail. Your backend should handle these
409 * error conditions appropriately.
411 * This function should not generate any bus I/O and should not block.
412 * If I/O is required (e.g. reading the active configuration value), it is
413 * OK to ignore these suggestions :)
415 * This function is executed when the user wishes to retrieve a list
416 * of USB devices connected to the system.
418 * Return 0 on success, or a LIBUSB_ERROR code on failure.
420 int (*get_device_list)(struct libusb_context *ctx,
421 struct discovered_devs **discdevs);
423 /* Open a device for I/O and other USB operations. The device handle
424 * is preallocated for you, you can retrieve the device in question
425 * through handle->dev.
427 * Your backend should allocate any internal resources required for I/O
428 * and other operations so that those operations can happen (hopefully)
429 * without hiccup. This is also a good place to inform libusb that it
430 * should monitor certain file descriptors related to this device -
431 * see the usbi_add_pollfd() function.
433 * This function should not generate any bus I/O and should not block.
435 * This function is called when the user attempts to obtain a device
436 * handle for a device.
440 * - LIBUSB_ERROR_ACCESS if the user has insufficient permissions
441 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since
443 * - another LIBUSB_ERROR code on other failure
445 * Do not worry about freeing the handle on failed open, the upper layers
448 int (*open)(struct libusb_device_handle *handle);
450 /* Close a device such that the handle cannot be used again. Your backend
451 * should destroy any resources that were allocated in the open path.
452 * This may also be a good place to call usbi_remove_pollfd() to inform
453 * libusb of any file descriptors associated with this device that should
454 * no longer be monitored.
456 * This function is called when the user closes a device handle.
458 void (*close)(struct libusb_device_handle *handle);
460 /* Retrieve the device descriptor from a device.
462 * The descriptor should be retrieved from memory, NOT via bus I/O to the
463 * device. This means that you may have to cache it in a private structure
464 * during get_device_list enumeration. Alternatively, you may be able
465 * to retrieve it from a kernel interface (some Linux setups can do this)
466 * still without generating bus I/O.
468 * This function is expected to write DEVICE_DESC_LENGTH (18) bytes into
469 * buffer, which is guaranteed to be big enough.
471 * This function is called when sanity-checking a device before adding
472 * it to the list of discovered devices, and also when the user requests
473 * to read the device descriptor.
475 * This function is expected to return the descriptor in bus-endian format
476 * (LE). If it returns the multi-byte values in host-endian format,
477 * set the host_endian output parameter to "1".
479 * Return 0 on success or a LIBUSB_ERROR code on failure.
481 int (*get_device_descriptor)(struct libusb_device *device,
482 unsigned char *buffer, int *host_endian);
484 /* Get the ACTIVE configuration descriptor for a device.
486 * The descriptor should be retrieved from memory, NOT via bus I/O to the
487 * device. This means that you may have to cache it in a private structure
488 * during get_device_list enumeration. You may also have to keep track
489 * of which configuration is active when the user changes it.
491 * This function is expected to write len bytes of data into buffer, which
492 * is guaranteed to be big enough. If you can only do a partial write,
493 * return an error code.
495 * This function is expected to return the descriptor in bus-endian format
496 * (LE). If it returns the multi-byte values in host-endian format,
497 * set the host_endian output parameter to "1".
501 * - LIBUSB_ERROR_NOT_FOUND if the device is in unconfigured state
502 * - another LIBUSB_ERROR code on other failure
504 int (*get_active_config_descriptor)(struct libusb_device *device,
505 unsigned char *buffer, size_t len, int *host_endian);
507 /* Get a specific configuration descriptor for a device.
509 * The descriptor should be retrieved from memory, NOT via bus I/O to the
510 * device. This means that you may have to cache it in a private structure
511 * during get_device_list enumeration.
513 * The requested descriptor is expressed as a zero-based index (i.e. 0
514 * indicates that we are requesting the first descriptor). The index does
515 * not (necessarily) equal the bConfigurationValue of the configuration
518 * This function is expected to write len bytes of data into buffer, which
519 * is guaranteed to be big enough. If you can only do a partial write,
520 * return an error code.
522 * This function is expected to return the descriptor in bus-endian format
523 * (LE). If it returns the multi-byte values in host-endian format,
524 * set the host_endian output parameter to "1".
526 * Return 0 on success or a LIBUSB_ERROR code on failure.
528 int (*get_config_descriptor)(struct libusb_device *device,
529 uint8_t config_index, unsigned char *buffer, size_t len,
532 /* Get the bConfigurationValue for the active configuration for a device.
533 * Optional. This should only be implemented if you can retrieve it from
534 * cache (don't generate I/O).
536 * If you cannot retrieve this from cache, either do not implement this
537 * function, or return LIBUSB_ERROR_NOT_SUPPORTED. This will cause
538 * libusb to retrieve the information through a standard control transfer.
540 * This function must be non-blocking.
543 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
545 * - LIBUSB_ERROR_NOT_SUPPORTED if the value cannot be retrieved without
547 * - another LIBUSB_ERROR code on other failure.
549 int (*get_configuration)(struct libusb_device_handle *handle, int *config);
551 /* Set the active configuration for a device.
553 * A configuration value of -1 should put the device in unconfigured state.
555 * This function can block.
559 * - LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
560 * - LIBUSB_ERROR_BUSY if interfaces are currently claimed (and hence
561 * configuration cannot be changed)
562 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
564 * - another LIBUSB_ERROR code on other failure.
566 int (*set_configuration)(struct libusb_device_handle *handle, int config);
568 /* Claim an interface. When claimed, the application can then perform
569 * I/O to an interface's endpoints.
571 * This function should not generate any bus I/O and should not block.
572 * Interface claiming is a logical operation that simply ensures that
573 * no other drivers/applications are using the interface, and after
574 * claiming, no other drivers/applicatiosn can use the interface because
579 * - LIBUSB_ERROR_NOT_FOUND if the interface does not exist
580 * - LIBUSB_ERROR_BUSY if the interface is in use by another driver/app
581 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
583 * - another LIBUSB_ERROR code on other failure
585 int (*claim_interface)(struct libusb_device_handle *handle, int interface_number);
587 /* Release a previously claimed interface.
589 * This function should also generate a SET_INTERFACE control request,
590 * resetting the alternate setting of that interface to 0. It's OK for
591 * this function to block as a result.
593 * You will only ever be asked to release an interface which was
594 * successfully claimed earlier.
598 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
600 * - another LIBUSB_ERROR code on other failure
602 int (*release_interface)(struct libusb_device_handle *handle, int interface_number);
604 /* Set the alternate setting for an interface.
606 * You will only ever be asked to set the alternate setting for an
607 * interface which was successfully claimed earlier.
609 * It's OK for this function to block.
613 * - LIBUSB_ERROR_NOT_FOUND if the alternate setting does not exist
614 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
616 * - another LIBUSB_ERROR code on other failure
618 int (*set_interface_altsetting)(struct libusb_device_handle *handle,
619 int interface_number, int altsetting);
621 /* Clear a halt/stall condition on an endpoint.
623 * It's OK for this function to block.
627 * - LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
628 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
630 * - another LIBUSB_ERROR code on other failure
632 int (*clear_halt)(struct libusb_device_handle *handle,
633 unsigned char endpoint);
635 /* Perform a USB port reset to reinitialize a device.
637 * If possible, the handle should still be usable after the reset
638 * completes, assuming that the device descriptors did not change during
639 * reset and all previous interface state can be restored.
641 * If something changes, or you cannot easily locate/verify the resetted
642 * device, return LIBUSB_ERROR_NOT_FOUND. This prompts the application
643 * to close the old handle and re-enumerate the device.
647 * - LIBUSB_ERROR_NOT_FOUND if re-enumeration is required, or if the device
648 * has been disconnected since it was opened
649 * - another LIBUSB_ERROR code on other failure
651 int (*reset_device)(struct libusb_device_handle *handle);
653 /* Determine if a kernel driver is active on an interface. Optional.
655 * The presence of a kernel driver on an interface indicates that any
656 * calls to claim_interface would fail with the LIBUSB_ERROR_BUSY code.
659 * - 0 if no driver is active
660 * - 1 if a driver is active
661 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
663 * - another LIBUSB_ERROR code on other failure
665 int (*kernel_driver_active)(struct libusb_device_handle *handle,
666 int interface_number);
668 /* Detach a kernel driver from an interface. Optional.
670 * After detaching a kernel driver, the interface should be available
675 * - LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
676 * - LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
677 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
679 * - another LIBUSB_ERROR code on other failure
681 int (*detach_kernel_driver)(struct libusb_device_handle *handle,
682 int interface_number);
684 /* Attach a kernel driver to an interface. Optional.
686 * Reattach a kernel driver to the device.
690 * - LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
691 * - LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
692 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
694 * - LIBUSB_ERROR_BUSY if a program or driver has claimed the interface,
695 * preventing reattachment
696 * - another LIBUSB_ERROR code on other failure
698 int (*attach_kernel_driver)(struct libusb_device_handle *handle,
699 int interface_number);
701 /* Destroy a device. Optional.
703 * This function is called when the last reference to a device is
704 * destroyed. It should free any resources allocated in the get_device_list
707 void (*destroy_device)(struct libusb_device *dev);
709 /* Submit a transfer. Your implementation should take the transfer,
710 * morph it into whatever form your platform requires, and submit it
713 * This function must not block.
717 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
718 * - another LIBUSB_ERROR code on other failure
720 int (*submit_transfer)(struct usbi_transfer *itransfer);
722 /* Cancel a previously submitted transfer.
724 * This function must not block. The transfer cancellation must complete
725 * later, resulting in a call to usbi_handle_transfer_cancellation()
726 * from the context of handle_events.
728 int (*cancel_transfer)(struct usbi_transfer *itransfer);
730 /* Clear a transfer as if it has completed or cancelled, but do not
731 * report any completion/cancellation to the library. You should free
732 * all private data from the transfer as if you were just about to report
733 * completion or cancellation.
735 * This function might seem a bit out of place. It is used when libusb
736 * detects a disconnected device - it calls this function for all pending
737 * transfers before reporting completion (with the disconnect code) to
738 * the user. Maybe we can improve upon this internal interface in future.
740 void (*clear_transfer_priv)(struct usbi_transfer *itransfer);
742 /* Handle any pending events. This involves monitoring any active
743 * transfers and processing their completion or cancellation.
745 * The function is passed an array of pollfd structures (size nfds)
746 * as a result of the poll() system call. The num_ready parameter
747 * indicates the number of file descriptors that have reported events
748 * (i.e. the poll() return value). This should be enough information
749 * for you to determine which actions need to be taken on the currently
752 * For any cancelled transfers, call usbi_handle_transfer_cancellation().
753 * For completed transfers, call usbi_handle_transfer_completion().
754 * For control/bulk/interrupt transfers, populate the "transferred"
755 * element of the appropriate usbi_transfer structure before calling the
756 * above functions. For isochronous transfers, populate the status and
757 * transferred fields of the iso packet descriptors of the transfer.
759 * This function should also be able to detect disconnection of the
760 * device, reporting that situation with usbi_handle_disconnect().
762 * When processing an event related to a transfer, you probably want to
763 * take usbi_transfer.lock to prevent races. See the documentation for
764 * the usbi_transfer structure.
766 * Return 0 on success, or a LIBUSB_ERROR code on failure.
768 int (*handle_events)(struct libusb_context *ctx,
769 struct pollfd *fds, nfds_t nfds, int num_ready);
771 /* Get time from specified clock. At least two clocks must be implemented
772 by the backend: USBI_CLOCK_REALTIME, and USBI_CLOCK_MONOTONIC.
774 Description of clocks:
775 USBI_CLOCK_REALTIME : clock returns time since system epoch.
776 USBI_CLOCK_MONOTONIC: clock returns time since unspecified start
779 int (*clock_gettime)(int clkid, struct timespec *tp);
781 #ifdef USBI_TIMERFD_AVAILABLE
782 /* clock ID of the clock that should be used for timerfd */
783 clockid_t (*get_timerfd_clockid)(void);
786 /* Number of bytes to reserve for per-device private backend data.
787 * This private data area is accessible through the "os_priv" field of
788 * struct libusb_device. */
789 size_t device_priv_size;
791 /* Number of bytes to reserve for per-handle private backend data.
792 * This private data area is accessible through the "os_priv" field of
793 * struct libusb_device. */
794 size_t device_handle_priv_size;
796 /* Number of bytes to reserve for per-transfer private backend data.
797 * This private data area is accessible by calling
798 * usbi_transfer_get_os_priv() on the appropriate usbi_transfer instance.
800 size_t transfer_priv_size;
802 /* Mumber of additional bytes for os_priv for each iso packet.
803 * Can your backend use this? */
804 /* FIXME: linux can't use this any more. if other OS's cannot either,
805 * then remove this */
806 size_t add_iso_packet_size;
809 extern const struct usbi_os_backend * const usbi_backend;
811 extern const struct usbi_os_backend linux_usbfs_backend;
812 extern const struct usbi_os_backend darwin_backend;