windows - 当我在 Windows 上的 HID 设备上执行 ReadFile() 时会发生什么？

Question

当我对 CreateFile(HID_DEVICE_NAME,...) 提供的句柄执行 ReadFile/WriteFile 时，HID 操作方面会发生什么情况？

它是向 HID 设备(在我的例子中是 USB)发出直接写入/读取请求，还是在底层驱动程序的某处进行转换以读取具有此类 ID 的最后缓存的 HID 报告？

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ReadFile 调用:

syncDevice.OutputReportBuffer[0] = 0;
syncDevice.OutputReportBuffer[1] = reportID;
HANDLE writeHandle = CreateFile(pDevice->DevicePath, GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, 0, OPEN_EXISTING, 0, 0);
HANDLE readHandle = CreateFile(pDevice->DevicePath, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, 0, OPEN_EXISTING, 0, 0);
success = WriteFile(writeHandle, (void*) syncDevice.OutputReportBuffer, syncDevice.Caps.OutputReportByteLength, &bytecnt, 0);
success = ReadFile(readHandle, syncDevice.InputReportBuffer, syncDevice.Caps.InputReportByteLength, &bytecnt, 0);

Answer 1

来自 USB Complete by Jan Axelson :

The Windows HID driver causes the host controller to request Input reports. The driver stores received reports in a buffer. ReadFile retrieves one or more reports from the buffer. If the buffer is empty, ReadFile waits for a report to arrive. In other words, ReadFile doesn’t cause a device to send a report but just reads reports that the driver has requested.

WriteFile sends an Output report. The function uses an interrupt transfer if the HID has an interrupt OUT endpoint and the operating system is later than Windows 98 Gold. Otherwise, WriteFile uses a control transfer with a Set Report request. If using interrupt transfers, WriteFile will wait if the device NAKs. If using control transfers, WriteFile returns with an error code on failure or a timeout.