scsi-disk: support emulated TO_DEV requests

This adds the implementation of write_data for the emulated
command case.  The first time through it asks for more data,
the second time it finishes the processing of the command.

MODE SELECT and MODE SELECT(10) can now be re-enabled, but they
will not do much.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/scsi-disk.c

@@ -1274,7 +1274,26 @@ static void scsi_disk_emulate_read_data(SCSIRequest *req)
 
 static void scsi_disk_emulate_write_data(SCSIRequest *req)
 {
-    abort();
+    SCSIDiskReq *r = DO_UPCAST(SCSIDiskReq, req, req);
+
+    if (r->iov.iov_len) {
+        int buflen = r->iov.iov_len;
+        DPRINTF("Write buf_len=%zd\n", buflen);
+        r->iov.iov_len = 0;
+        scsi_req_data(&r->req, buflen);
+        return;
+    }
+
+    switch (req->cmd.buf[0]) {
+    case MODE_SELECT:
+    case MODE_SELECT_10:
+        /* This also clears the sense buffer for REQUEST SENSE.  */
+        scsi_req_complete(&r->req, GOOD);
+        break;
+
+    default:
+        abort();
+    }
 }
 
 static int32_t scsi_disk_emulate_command(SCSIRequest *req, uint8_t *buf)
@@ -1283,7 +1302,7 @@ static int32_t scsi_disk_emulate_command(SCSIRequest *req, uint8_t *buf)
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, req->dev);
     uint64_t nb_sectors;
     uint8_t *outbuf;
-    int buflen = 0;
+    int buflen;
 
     switch (req->cmd.buf[0]) {
     case INQUIRY:
@@ -1309,7 +1328,6 @@ static int32_t scsi_disk_emulate_command(SCSIRequest *req, uint8_t *buf)
         break;
     }
 
-    assert(req->cmd.mode != SCSI_XFER_TO_DEV);
     if (!r->iov.iov_base) {
         /*
          * FIXME: we shouldn't return anything bigger than 4k, but the code
@@ -1326,6 +1344,7 @@ static int32_t scsi_disk_emulate_command(SCSIRequest *req, uint8_t *buf)
         r->iov.iov_base = qemu_blockalign(s->qdev.conf.bs, r->buflen);
     }
 
+    buflen = req->cmd.xfer;
     outbuf = r->iov.iov_base;
     switch (req->cmd.buf[0]) {
     case TEST_UNIT_READY:
@@ -1500,7 +1519,6 @@ static int32_t scsi_disk_emulate_command(SCSIRequest *req, uint8_t *buf)
             goto illegal_lba;
         }
         break;
-#if 0
     case MODE_SELECT:
         DPRINTF("Mode Select(6) (len %lu)\n", (long)r->req.cmd.xfer);
         /* We don't support mode parameter changes.
@@ -1517,7 +1535,6 @@ static int32_t scsi_disk_emulate_command(SCSIRequest *req, uint8_t *buf)
             goto illegal_request;
         }
         break;
-#endif
     case WRITE_SAME_10:
         nb_sectors = lduw_be_p(&req->cmd.buf[7]);
         goto write_same;
@@ -1552,7 +1569,12 @@ static int32_t scsi_disk_emulate_command(SCSIRequest *req, uint8_t *buf)
     if (r->iov.iov_len == 0) {
         scsi_req_complete(&r->req, GOOD);
     }
-    return r->iov.iov_len;
+    if (r->req.cmd.mode == SCSI_XFER_TO_DEV) {
+        assert(r->iov.iov_len == req->cmd.xfer);
+        return -r->iov.iov_len;
+    } else {
+        return r->iov.iov_len;
+    }
 
 illegal_request:
     if (r->req.status == -1) {
@@ -1834,10 +1856,8 @@ static const SCSIReqOps *const scsi_disk_reqops_dispatch[256] = {
     [REQUEST_SENSE]                   = &scsi_disk_emulate_reqops,
     [SYNCHRONIZE_CACHE]               = &scsi_disk_emulate_reqops,
     [SEEK_10]                         = &scsi_disk_emulate_reqops,
-#if 0
     [MODE_SELECT]                     = &scsi_disk_emulate_reqops,
     [MODE_SELECT_10]                  = &scsi_disk_emulate_reqops,
-#endif
     [WRITE_SAME_10]                   = &scsi_disk_emulate_reqops,
     [WRITE_SAME_16]                   = &scsi_disk_emulate_reqops,