206 lines
9.2 KiB
Plaintext
206 lines
9.2 KiB
Plaintext
When the kernel detects a connected USB device, it configures the device in
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terms of USB protocol - SET_ADDRESS + SET_CONFIGURATION, the first
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configuration is always selected. The kernel also reads device descriptor to
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print some information, reads and parses configuration descriptor. For every
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interface the kernel looks for class code of this interface and loads the
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corresponding COFF driver. Currently the correspondence is hardcoded into
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the kernel code and looks as follows: 3 = usbhid.obj, 7 = usbprint.obj,
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8 = usbstor.obj, 9 is handled by the kernel itself, other = usbother.obj.
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The driver must be standard driver in COFF format, exporting procedure
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named "START" and a variable named "version". Loader calls "START" procedure
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as stdcall with one parameter DRV_ENTRY = 1; if initialization is successful,
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the "START" procedure is also called by shutdown code with one parameter
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DRV_EXIT = -1.
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The driver must register itself as a USB driver in "START" procedure.
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This is done by call to exported function RegUSBDriver and passing the returned
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value as result of "START" procedure.
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void* __stdcall RegUSBDriver(
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const char* name,
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void* handler,
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const USBFUNC* usbfunc
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);
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The parameter 'name' should match the name of driver, "usbhid" for usbhid.obj.
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The parameter 'handler' is optional; if it is non-NULL, it should point to
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the standard handler for IOCTL interface as in non-USB drivers.
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The parameter 'usbfunc' is a pointer to the following structure:
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struc USBFUNC
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{
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.strucsize dd ? ; size of the structure, including this field
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.add_device dd ? ; pointer to AddDevice function in the driver
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; required
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.device_disconnect dd ? ; pointer to DeviceDisconnected function in the driver
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; optional, may be NULL
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; other functions may be added in the future
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}
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The driver should implement the function
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void* __stdcall AddDevice(
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void* pipe0,
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void* configdescr,
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void* interfacedescr
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);
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The parameter 'pipe0' is a handle of the control pipe for endpoint zero
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of the device. It can be used as the argument of USBControlTransferAsync.
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The parameter 'configdescr' points to USB configuration descriptor
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and all associated data, as returned by GET_DESCRIPTOR request.
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The total length of all associated data is contained in the configuration
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descriptor.
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The parameter 'interfacedescr' points to USB interface descriptor corresponding
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to the interface which is initializing. This is a pointer inside data
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associated with the configuration descriptor.
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Note that one device can implement many interfaces, so AddDevice may be
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called several times with the same 'configdescr' and different 'interfacedescr'.
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The returned value NULL means that the initialization has failed.
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Any other value means that configuration was successful; the kernel does not
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try to interpret the value. It can be, for example, pointer to the internal
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data allocated with Kmalloc, or index in some internal table.
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The driver can implement the function
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void __stdcall DeviceDisconnected(
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void* devicedata
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);
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If this function is implemented, the kernel calls it when the device is
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disconnected, passing the returned value of AddDevice as 'devicedata'.
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The driver can use the following functions exported by the kernel.
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void* __stdcall USBOpenPipe(
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void* pipe0,
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int endpoint,
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int maxpacketsize,
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int type,
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int interval
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);
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The parameter 'pipe0' is a handle of the pipe for endpoint zero for
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the device, as passed to AddDevice. It is used to identify the device.
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The parameter 'endpoint' is endpoint number as defined by USB. Lower
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4 bits form the number itself, bit 7 - highest bit of low byte -
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is 0/1 for OUT/IN endpoints, other bits should be zero.
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The parameter 'maxpacketsize' sets the maximum packet size for this pipe.
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The parameter 'type' selects the type of the endpoint as defined by USB:
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0 = control, 1 = isochronous (not supported yet), 2 = bulk, 3 = interrupt.
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The parameter 'interval' is ignored for control and bulk endpoints.
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For interrupt endpoints, it sets the polling interval in milliseconds.
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The function returns a handle to the pipe or NULL on failure.
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The output handle becomes invalid when a) it is explicitly closed with
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the following function or b) the function DeviceDisconnected provided
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by the driver returns.
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void __stdcall USBClosePipe(
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void* pipe
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);
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Releases all resources associated with the given pipe. The only parameter
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must be a handle returned by USBOpenPipe.
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When a device is disconnected, all associated pipes are closed by the kernel;
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there is no need to ever call this function if all pipes are used continuously
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while a device is connected.
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void* __stdcall USBNormalTransferAsync(
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void* pipe,
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void* buffer,
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int size,
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void* callback,
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void* calldata,
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int flags
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);
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void* __stdcall USBControlTransferAsync(
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void* pipe,
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void* setup,
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void* buffer,
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int size,
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void* callback,
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void* calldata,
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int flags
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);
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The first function inserts a bulk or interrupt transfer to the transfer queue
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for given pipe. Type and direction of transfer are fixed for bulk and interrupt
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endpoints and are set in USBOpenPipe. The second function inserts a control
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transfer to the transfer queue for given pipe. Direction of a control transfer
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is concluded from 'setup' packet, bit 7 of byte 0 is set for IN transfers
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and cleared for OUT transfers. These function return immediately; when data
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are transferred, the callback function will be called.
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The parameter 'pipe' is a handle returned by USBOpenPipe.
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The parameter 'setup' of USBControlTransferAsync points to 8-byte
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configuration packet as defined by USB.
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The parameter 'buffer' is a pointer to buffer. For IN transfers, it will be
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filled with the data. For OUT transfers, it should contain data to be
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transferred. It can be NULL for an empty transfer or if no additional data are
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required for a control transfer.
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The parameter 'size' is size of data to transfer. It can be 0 for an empty
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transfer or if no additional data are required for a control transfer.
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The parameter 'callback' is a pointer to a function which will be called
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when the transfer will be done.
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The parameter 'calldata' will be passed as is to the callback function.
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For example, it can be NULL, it can be a pointer to device data or it can be
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a pointer to data used to pass additional parameters between caller and
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callback. The transfer-specific data can also be associated with 'buffer',
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preceding (negative offsets from 'buffer') or following (offsets more than
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or equal to 'size') the buffer itself.
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The parameter 'flags' is the bitmask.
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The bit 0 is ignored for OUT transfers, for IN transfers it controls whether
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the device can transfer less data than 'size' bytes. If the bit is 0, a small
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transfer is an error; if the bit is 1, a small transfer is OK.
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All other bits are reserved and should be zero.
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The returned value is NULL if an error occured and non-NULL if the transfer
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was successfully queued. If an error will occur later, the callback function
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will be notified.
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void __stdcall CallbackFunction(
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void* pipe,
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int status,
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void* buffer,
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int length,
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void* calldata
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);
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The parameters 'pipe', 'buffer', 'calldata' are the same as for the
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corresponding USB*TransferAsync.
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The parameter 'length' is the number of bytes transferred. For
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control transfers, this includes 8 bytes from SETUP stage, so
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0 means that SETUP stage failed and 'size'+8 means full transfer.
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The parameter 'status' is nonzero if an error occured.
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USB_STATUS_OK = 0 ; no error
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USB_STATUS_CRC = 1 ; CRC error
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USB_STATUS_BITSTUFF = 2 ; bit stuffing violation
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USB_STATUS_TOGGLE = 3 ; data toggle mismatch
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USB_STATUS_STALL = 4 ; device returned STALL
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USB_STATUS_NORESPONSE = 5 ; device not responding
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USB_STATUS_PIDCHECK = 6 ; invalid PID check bits
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USB_STATUS_WRONGPID = 7 ; unexpected PID value
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USB_STATUS_OVERRUN = 8 ; too many data from endpoint
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USB_STATUS_UNDERRUN = 9 ; too few data from endpoint
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USB_STATUS_BUFOVERRUN = 12 ; overflow of internal controller buffer
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USB_STATUS_BUFUNDERRUN = 13 ; underflow of internal controller buffer
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USB_STATUS_CLOSED = 16 ; pipe closed, either explicitly with USBClosePipe
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; or due to device disconnect
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If several transfers are queued for the same pipe, their callback functions
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are called in the same order as they were queued.
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When a pipe is closed, either explicitly with USBClosePipe, or
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implicitly due to device disconnect, all callback functions are called
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with USB_STATUS_CLOSED. The call to DeviceDisconnected() occurs after
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all callbacks.
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void* __stdcall USBGetParam(void* pipe0, int param);
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Returns miscellaneous parameters of the device.
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pipe0 is the pointer to the config pipe.
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param = 0: return pointer to device descriptor
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param = 1: return pointer to config descriptor, same as passed to AddDevice
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param = 2: return speed at which the device is operating, one of
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USB_SPEED_FS = 0 ; full-speed
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USB_SPEED_LS = 1 ; low-speed
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USB_SPEED_HS = 2 ; high-speed
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