Modify EndpointInfo to provide meaningful data rather than raw USB

descriptor values. E.g. for the user, the distinction between
MaxIsoPkt and MaxPktSize is irrelevant, only the calculated max packet
size matters.

usb/transfer_test.go

@@ -27,8 +27,7 @@ func TestNewTransfer(t *testing.T) {
 		desc        string
 		dir         EndpointDirection
 		tt          TransferType
-		maxPkt      uint16
-		maxIso      uint32
+		maxPkt      uint32
 		buf         int
 		timeout     time.Duration
 		wantIso     int
@@ -48,18 +47,16 @@ func TestNewTransfer(t *testing.T) {
 			desc:       "iso out transfer, 3 * 1024B packets",
 			dir:        EndpointDirectionOut,
 			tt:         TransferTypeIsochronous,
-			maxPkt:     2<<11 + 1024,
-			maxIso:     3 * 1024,
+			maxPkt:     3 * 1024,
 			buf:        10000,
 			wantLength: 10000,
 		},
 	} {
-		xfer, err := newUSBTransfer(nil, EndpointInfo{
-			Address:       uint8(tc.dir) | 0x02,
-			Attributes:    uint8(tc.tt),
+		xfer, err := newUSBTransfer(nil, &EndpointInfo{
+			Number:        2,
+			Direction:     tc.dir,
+			TransferType:  tc.tt,
 			MaxPacketSize: tc.maxPkt,
-			MaxIsoPacket:  tc.maxIso,
-			PollInterval:  1,
 		}, make([]byte, tc.buf), tc.timeout)
 
 		if err != nil {
@@ -80,11 +77,11 @@ func TestTransferProtocol(t *testing.T) {
 	xfers := make([]*usbTransfer, 2)
 	var err error
 	for i := 0; i < 2; i++ {
-		xfers[i], err = newUSBTransfer(nil, EndpointInfo{
-			Address:       0x86,
-			Attributes:    uint8(TransferTypeBulk),
+		xfers[i], err = newUSBTransfer(nil, &EndpointInfo{
+			Number:        6,
+			Direction:     EndpointDirectionIn,
+			TransferType:  TransferTypeBulk,
 			MaxPacketSize: 512,
-			PollInterval:  1,
 		}, make([]byte, 10240), time.Second)
 		if err != nil {
 			t.Fatalf("newUSBTransfer: %v", err)