+static int ata_passthrough_xfer_unit(SCSIDevice *dev, uint8_t *buf)
+{
+ int byte_block = (buf[2] >> 2) & 0x1;
+ int type = (buf[2] >> 4) & 0x1;
+ int xfer_unit;
+
+ if (byte_block) {
+ if (type) {
+ xfer_unit = dev->blocksize;
+ } else {
+ xfer_unit = 512;
+ }
+ } else {
+ xfer_unit = 1;
+ }
+
+ return xfer_unit;
+}
+
+static int ata_passthrough_12_xfer_size(SCSIDevice *dev, uint8_t *buf)
+{
+ int length = buf[2] & 0x3;
+ int xfer;
+ int unit = ata_passthrough_xfer_unit(dev, buf);
+
+ switch (length) {
+ case 0:
+ case 3: /* USB-specific. */
+ xfer = 0;
+ break;
+ case 1:
+ xfer = buf[3];
+ break;
+ case 2:
+ xfer = buf[4];
+ break;
+ }
+
+ return xfer * unit;
+}
+
+static int ata_passthrough_16_xfer_size(SCSIDevice *dev, uint8_t *buf)
+{
+ int extend = buf[1] & 0x1;
+ int length = buf[2] & 0x3;
+ int xfer;
+ int unit = ata_passthrough_xfer_unit(dev, buf);
+
+ switch (length) {
+ case 0:
+ case 3: /* USB-specific. */
+ xfer = 0;
+ break;
+ case 1:
+ xfer = buf[4];
+ xfer |= (extend ? buf[3] << 8 : 0);
+ break;
+ case 2:
+ xfer = buf[6];
+ xfer |= (extend ? buf[5] << 8 : 0);
+ break;
+ }
+
+ return xfer * unit;
+}
+