usb: use iovecs in USBPacket

Zap data pointer from USBPacket, add a QEMUIOVector instead.
Add a bunch of helper functions to manage USBPacket data.
Switch over users to the new interface.

Note that USBPacket->len was used for two purposes:  First to
pass in the buffer size and second to return the number of
transfered bytes or the status code on async transfers.  There
is a new result variable for the latter.  A new status code
was added to catch uninitialized result.

Nobody creates iovecs with more than one element (yet).
Some users are (temporarely) limited to iovecs with a single
element to keep the patch size as small as possible.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/hw/usb-serial.c b/hw/usb-serial.c
index 298c1e9d95..09731da485 100644
--- a/hw/usb-serial.c
+++ b/hw/usb-serial.c
@@ -361,10 +361,11 @@ static int usb_serial_handle_data(USBDevice *dev, USBPacket *p)
     USBSerialState *s = (USBSerialState *)dev;
     int ret = 0;
     uint8_t devep = p->devep;
-    uint8_t *data = p->data;
-    int len = p->len;
+    uint8_t *data = p->iov.iov[0].iov_base;
+    int len = p->iov.iov[0].iov_len;
     int first_len;
 
+    assert(p->iov.niov == 1); /* temporary */
     switch (p->pid) {
     case USB_TOKEN_OUT:
         if (devep != 2)