start_xmit(E1000State *s)
{
    PCIDevice *d = PCI_DEVICE(s);
    dma_addr_t base;
    struct e1000_tx_desc desc;
    uint32_t tdh_start = s->mac_reg[TDH], cause = E1000_ICS_TXQE;

    if (!(s->mac_reg[TCTL] & E1000_TCTL_EN)) {
        DBGOUT(TX, "tx disabled\n");
        return;
    }

    while (s->mac_reg[TDH] != s->mac_reg[TDT]) {
        base = tx_desc_base(s) +
               sizeof(struct e1000_tx_desc) * s->mac_reg[TDH];
        pci_dma_read(d, base, &desc, sizeof(desc));

        DBGOUT(TX, "index %d: %p : %x %x\n", s->mac_reg[TDH],
               (void *)(intptr_t)desc.buffer_addr, desc.lower.data,
               desc.upper.data);

        process_tx_desc(s, &desc);
        cause |= txdesc_writeback(s, base, &desc);

        if (++s->mac_reg[TDH] * sizeof(desc) >= s->mac_reg[TDLEN])
            s->mac_reg[TDH] = 0;
        /*
         * the following could happen only if guest sw assigns
         * bogus values to TDT/TDLEN.
         * there's nothing too intelligent we could do about this.
         */
        if (s->mac_reg[TDH] == tdh_start ||
            tdh_start >= s->mac_reg[TDLEN] / sizeof(desc)) {
            DBGOUT(TXERR, "TDH wraparound @%x, TDT %x, TDLEN %x\n",
                   tdh_start, s->mac_reg[TDT], s->mac_reg[TDLEN]);
            break;
        }
    }
    set_ics(s, 0, cause);
}
Unknown