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weidongshan
@@ -85,7 +85,248 @@ int API_EXPORTED libusb_init(libusb_context **ctx);
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#### 2.2.2 获取设备
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可以使用`libusb_get_device_list`取出所有设备，函数接口如下：
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```c
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/** @ingroup libusb_dev
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* Returns a list of USB devices currently attached to the system. This is
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* your entry point into finding a USB device to operate.
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*
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* You are expected to unreference all the devices when you are done with
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* them, and then free the list with libusb_free_device_list(). Note that
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* libusb_free_device_list() can unref all the devices for you. Be careful
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* not to unreference a device you are about to open until after you have
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* opened it.
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*
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* This return value of this function indicates the number of devices in
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* the resultant list. The list is actually one element larger, as it is
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* NULL-terminated.
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*
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* \param ctx the context to operate on, or NULL for the default context
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* \param list output location for a list of devices. Must be later freed with
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* libusb_free_device_list().
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* \returns the number of devices in the outputted list, or any
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* \ref libusb_error according to errors encountered by the backend.
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*/
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ssize_t API_EXPORTED libusb_get_device_list(libusb_context *ctx,
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libusb_device ***list);
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```
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调用此函数后，所有设备的信息存入list，然后遍历list，找到想操作的设备。这个函数内部会分配list的空间，所以用完后要释放掉，使用以下函数释放：
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```c
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/** \ingroup libusb_dev
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* Frees a list of devices previously discovered using
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* libusb_get_device_list(). If the unref_devices parameter is set, the
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* reference count of each device in the list is decremented by 1.
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* \param list the list to free
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* \param unref_devices whether to unref the devices in the list
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*/
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void API_EXPORTED libusb_free_device_list(libusb_device **list,
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int unref_devices);
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```
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#### 2.2.3 打开/关闭设备
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使用libusb_get_device_list得到设备列表后，可以选择里面的某个设备，然后调用libusb_open：
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```c
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/** \ingroup libusb_dev
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* Open a device and obtain a device handle. A handle allows you to perform
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* I/O on the device in question.
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*
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* Internally, this function adds a reference to the device and makes it
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* available to you through libusb_get_device(). This reference is removed
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* during libusb_close().
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*
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* This is a non-blocking function; no requests are sent over the bus.
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*
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* \param dev the device to open
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* \param dev_handle output location for the returned device handle pointer. Only
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* populated when the return code is 0.
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* \returns 0 on success
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* \returns \ref LIBUSB_ERROR_NO_MEM on memory allocation failure
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* \returns \ref LIBUSB_ERROR_ACCESS if the user has insufficient permissions
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* \returns \ref LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
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* \returns another LIBUSB_ERROR code on other failure
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*/
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int API_EXPORTED libusb_open(libusb_device *dev,
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libusb_device_handle **dev_handle);
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```
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使用libusb_open函数打开USB设备后，可以得到一个句柄：libusb_device_handle。以后调用各种数据传输函数时，就是使用libusb_device_handle。
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使用完毕后，调用libusb_close关闭设备，函数原型如下：
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```c
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/** \ingroup libusb_dev
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* Close a device handle. Should be called on all open handles before your
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* application exits.
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*
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* Internally, this function destroys the reference that was added by
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* libusb_open() on the given device.
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*
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* This is a non-blocking function; no requests are sent over the bus.
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*
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* \param dev_handle the device handle to close
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*/
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void API_EXPORTED libusb_close(libusb_device_handle *dev_handle);
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```
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#### 2.2.4 根据ID打开设备
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如果知道设备的VID、PID，那么可以使用libusb_open_device_with_vid_pid来找到它、打开它。这个函数的内部，先使用`libusb_get_device_list`列出所有设备，然后遍历它们根据ID选出设备，接着调用libusb_open打开它，最后调用libusb_free_device_list释放设备。
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libusb_open_device_with_vid_pid函数原型如下：
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```c
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/** \ingroup libusb_dev
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* Convenience function for finding a device with a particular
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* <tt>idVendor</tt>/<tt>idProduct</tt> combination. This function is intended
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* for those scenarios where you are using libusb to knock up a quick test
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* application - it allows you to avoid calling libusb_get_device_list() and
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* worrying about traversing/freeing the list.
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*
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* This function has limitations and is hence not intended for use in real
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* applications: if multiple devices have the same IDs it will only
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* give you the first one, etc.
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*
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* \param ctx the context to operate on, or NULL for the default context
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* \param vendor_id the idVendor value to search for
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* \param product_id the idProduct value to search for
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* \returns a device handle for the first found device, or NULL on error
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* or if the device could not be found. */
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DEFAULT_VISIBILITY
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libusb_device_handle * LIBUSB_CALL libusb_open_device_with_vid_pid(
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libusb_context *ctx, uint16_t vendor_id, uint16_t product_id);
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```
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#### 2.2.5 detach/attach驱动
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使用libusb访问USB设备时，需要先移除(detach)设备原来的驱动程序，然后安装(attach)libusb专用的驱动程序。有两种办法：
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* 方法1：
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```c
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// 只是设置一个标记位表示libusb_claim_interface
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// 使用libusb_claim_interface时会detach原来的驱动
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libusb_set_auto_detach_kernel_driver(hdev, 1);
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// 给interface安装驱动程序，标记这个interface已经被使用认领了
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libusb_claim_interface(hdev, interface_number);
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```
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* 方法2：
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```c
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// detach原来的驱动
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libusb_detach_kernel_driver(hdev, interface_number);
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// 给interface安装驱动程序，标记这个interface已经被使用认领了
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libusb_claim_interface(hdev, interface_number);
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```
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函数`libusb_detach_kernel_driver`原型如下：
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```c
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* Detach a kernel driver from an interface. If successful, you will then be
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* able to claim the interface and perform I/O.
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*
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* This functionality is not available on Windows.
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*
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* Note that libusb itself also talks to the device through a special kernel
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* driver, if this driver is already attached to the device, this call will
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* not detach it and return \ref LIBUSB_ERROR_NOT_FOUND.
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*
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* \param dev_handle a device handle
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* \param interface_number the interface to detach the driver from
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* \returns 0 on success
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* \returns \ref LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
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* \returns \ref LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
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* \returns \ref LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
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* \returns \ref LIBUSB_ERROR_NOT_SUPPORTED on platforms where the functionality
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* is not available
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* \returns another LIBUSB_ERROR code on other failure
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* \see libusb_kernel_driver_active()
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*/
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int API_EXPORTED libusb_detach_kernel_driver(libusb_device_handle *dev_handle,
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int interface_number);
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```
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函数`libusb_claim_interface`原型如下：
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```c
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/** \ingroup libusb_dev
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* Claim an interface on a given device handle. You must claim the interface
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* you wish to use before you can perform I/O on any of its endpoints.
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*
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* It is legal to attempt to claim an already-claimed interface, in which
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* case libusb just returns 0 without doing anything.
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*
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* If auto_detach_kernel_driver is set to 1 for <tt>dev</tt>, the kernel driver
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* will be detached if necessary, on failure the detach error is returned.
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*
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* Claiming of interfaces is a purely logical operation; it does not cause
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* any requests to be sent over the bus. Interface claiming is used to
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* instruct the underlying operating system that your application wishes
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* to take ownership of the interface.
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*
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* This is a non-blocking function.
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*
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* \param dev_handle a device handle
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* \param interface_number the <tt>bInterfaceNumber</tt> of the interface you
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* wish to claim
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* \returns 0 on success
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* \returns \ref LIBUSB_ERROR_NOT_FOUND if the requested interface does not exist
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* \returns \ref LIBUSB_ERROR_BUSY if another program or driver has claimed the
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* interface
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* \returns \ref LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
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* \returns a LIBUSB_ERROR code on other failure
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* \see libusb_set_auto_detach_kernel_driver()
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*/
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int API_EXPORTED libusb_claim_interface(libusb_device_handle *dev_handle,
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int interface_number);
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```
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使用完USB设备后，在调用libusb_close之前，应该`libusb_release_interface`释放接口：
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```c
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/** \ingroup libusb_dev
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* Release an interface previously claimed with libusb_claim_interface(). You
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* should release all claimed interfaces before closing a device handle.
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*
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* This is a blocking function. A SET_INTERFACE control request will be sent
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* to the device, resetting interface state to the first alternate setting.
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*
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* If auto_detach_kernel_driver is set to 1 for <tt>dev</tt>, the kernel
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* driver will be re-attached after releasing the interface.
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*
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* \param dev_handle a device handle
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* \param interface_number the <tt>bInterfaceNumber</tt> of the
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* previously-claimed interface
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* \returns 0 on success
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* \returns \ref LIBUSB_ERROR_NOT_FOUND if the interface was not claimed
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* \returns \ref LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
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* \returns another LIBUSB_ERROR code on other failure
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* \see libusb_set_auto_detach_kernel_driver()
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*/
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int API_EXPORTED libusb_release_interface(libusb_device_handle *dev_handle,
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int interface_number);
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```
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#### 2.2.6 描述符相关函数
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@@ -127,11 +368,17 @@ dnw是s3c2440时代的工具，使用它可以从PC给开发板传输文件。
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### 3.2 openocd
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### 3.2 adb
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### 3.3 openocd
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openocd是一个开源的USB JTAG调试软件，它也是使用libusb，涉及USB的操作代码如下。
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#### 3.2.1 找到设备
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#### 3.3.1 找到设备
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```c
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static int cmsis_dap_usb_open(struct cmsis_dap *dap, uint16_t vids[], uint16_t pids[], const char *serial)
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@@ -473,7 +720,7 @@ static int cmsis_dap_usb_open(struct cmsis_dap *dap, uint16_t vids[], uint16_t p
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#### 3.2.2 读写数据
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#### 3.3.2 读写数据
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```c
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static int cmsis_dap_usb_read(struct cmsis_dap *dap, int timeout_ms)
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