usb: add USB mass storage class support

src/machine/usb/msc/scsi_unmap.go

@@ -0,0 +1,91 @@
+package msc
+
+import (
+	"encoding/binary"
+	"machine/usb/msc/csw"
+	"machine/usb/msc/scsi"
+)
+
+type Error int
+
+const (
+	errorLBAOutOfRange Error = iota
+)
+
+func (e Error) Error() string {
+	switch e {
+	case errorLBAOutOfRange:
+		return "LBA out of range"
+	default:
+		return "unknown error"
+	}
+}
+
+func (m *msc) scsiUnmap(b []byte) {
+	// Execute Order 66 (0x42) to wipe out the blocks
+	// 3.54 Unmap Command (SBC-4)
+	// https://www.seagate.com/files/staticfiles/support/docs/manual/Interface%20manuals/100293068j.pdf
+	if m.readOnly {
+		m.sendScsiError(csw.StatusFailed, scsi.SenseDataProtect, scsi.SenseCodeWriteProtected)
+		return
+	}
+
+	// blockDescLen is the remaining length of block descriptors in the message, offset 8 bytes from
+	// the start of this packet
+	var blockDescLen uint16
+
+	// Decode the parameter list
+	msgLen := binary.BigEndian.Uint16(b[:2])
+	// Length of the block descriptor portion of the message
+	blockDescLen = binary.BigEndian.Uint16(b[2:4])
+	// Do some sanity checks on the message lengths (max 3 block descriptors to fit in one 64 byte packet)
+	if msgLen < 8 || blockDescLen < 16 || msgLen-blockDescLen != 6 || blockDescLen > (3*16) {
+		m.sendScsiError(csw.StatusFailed, scsi.SenseIllegalRequest, scsi.SenseCodeInvalidFieldInCDB)
+		return
+	}
+
+	// descEnd marks the end of the last full block descriptor in this packet
+	descEnd := int(blockDescLen + 8)
+
+	// Unmap the blocks we can from this packet
+	for i := 8; i < descEnd; i += 16 {
+		err := m.unmapBlocksFromDescriptor(b[i:], uint64(m.blockCount))
+		if err != nil {
+			// TODO: Might need a better error code here for device errors?
+			m.sendScsiError(csw.StatusFailed, scsi.SenseVolumeOverflow, scsi.SenseCodeLBAOutOfRange)
+			return
+		}
+	}
+
+	// FIXME: We need to handle erase block alignment
+
+	m.sentBytes += uint32(len(b))
+	if m.sentBytes >= m.totalBytes {
+		// Order 66 complete, send CSW to establish galactic empire
+		m.state = mscStateStatus
+		m.run([]byte{}, true)
+	}
+}
+
+func (m *msc) unmapBlocksFromDescriptor(b []byte, numBlocks uint64) error {
+	blockCount := binary.BigEndian.Uint32(b[8:12])
+	if blockCount == 0 {
+		// No blocks to unmap. Explicitly not an error per the spec
+		return nil
+	}
+	// This is technically a 64-bit LBA, but we can't address that many bytes
+	// let alone blocks, so we just use the lower 32 bits
+	lba := binary.BigEndian.Uint32(b[4:8])
+
+	// Make sure the unmap command doesn't extend past the end of the volume
+	if lba+blockCount > m.blockCount {
+		return errorLBAOutOfRange
+	}
+
+	// Convert the emulated block size to the underlying hardware erase block size
+	blockStart := int64(lba*m.blockSizeUSB) / m.dev.EraseBlockSize()
+	rawBlockCount := int64(blockCount*m.blockSizeUSB) / m.dev.EraseBlockSize()
+
+	// Unmap the blocks
+	return m.dev.EraseBlocks(blockStart, rawBlockCount)
+}