求知！！！

请问哪位大虾知道在DS自带的例子usbtherm的读例程中的
2, // request
该参数的2是怎样确定？

pCompInfo->m_pUrb = m_Usb.BuildVendorRequest(
pCompInfo->m_buffer, // transfer buffer
8, // transfer buffer size
0, // request reserved bits
2, // request
offset, // Value
TRUE, // In
FALSE, // Short Ok
NULL, // link urb
0, // index
URB_FUNCTION_VENDOR_ENDPOINT // function
);

Request
Specifies the request code for the device. The request code is defined by the USB class, or by the vendor of the device.

由写firmware的人定