fix: prevent inquiry hangs

Author: mikesmitty

src/machine/usb/msc/scsi.go

@@ -50,6 +50,7 @@ func (m *msc) scsiCmdBegin() {
 	default:
 		// We don't support this command, error out
 		m.sendScsiError(csw.StatusFailed, scsi.SenseIllegalRequest, scsi.SenseCodeInvalidCmdOpCode)
+		return
 	}
 
 	if len(m.buf) == 0 {

src/machine/usb/msc/scsi_inquiry.go

@@ -138,6 +138,11 @@ func (m *msc) scsiEvpdInquiry(cmd scsi.Cmd, pageCode uint8) {
 	// Set total bytes to the length of our response
 	m.queuedBytes = uint32(len(m.buf))
 	m.totalBytes = uint32(len(m.buf))
+
+	// Only send ZLP if the data length is a multiple of the max packet size
+	if m.totalBytes%m.maxPacketSize == 0 {
+		m.sendZLP = true
+	}
 }
 
 func (m *msc) scsiStdInquiry(cmd scsi.Cmd) {
@@ -162,4 +167,9 @@ func (m *msc) scsiStdInquiry(cmd scsi.Cmd) {
 	copy(m.buf[16:32], m.productID[:])
 	// bytes 32-35 - Product revision level
 	copy(m.buf[32:36], m.productRev[:])
+
+	// Only send ZLP if the data length is a multiple of the max packet size
+	if m.totalBytes%m.maxPacketSize == 0 {
+		m.sendZLP = true
+	}
 }