The Transmit Buffer; Transmitting The Buffer - Compaq Tru64 UNIX Installation Manual

in the middle. The mfree( ) routine is called to free any zero-length
memory buffers.
Otherwise, adds the length and sets the next memory buffer in the
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chain to the mp mbuf pointer.

9.2.3 Transmitting the Buffer

The following code shows how the el_start_locked( ) routine transmits
the buffer:
WRITE_DATA(sc, len | TX_INT);
dat = mtod(ms, unsigned char *);
len = ms->m_len;
while (ms != NULL) {
io_blockwrite((vm_offset_t)dat,
dat += (len & ~ 3);
ms = ms->m_next;
i = len % 4;
if (ms == NULL) {
if (i) {
val = 0;
for (j=0; j<i; j++)
val |= (*dat++ << (8*j));
WRITE_DATA(sc, val);
}
} else {
if (i) {
val = 0;
for (j=0; j<i; j++)
val |= (*dat++ << (8*j));
dat = mtod(ms, unsigned char *);
if (ms->m_len <= (4-i)) {
} else {
}
WRITE_DATA(sc, val);
} else {
dat = mtod(ms, unsigned char *);
len = ms->m_len;
}
}
}
Requests an interrupt upon completion of the transmit operation.
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9–6 Implementing the Start Section
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2
sc->data,
(u_long)(len & ~ 3),
HANDLE_LONGWORD);
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for (j=0; j<ms->m_len; j++)
val |= (*dat++ << (8*(j+i)));
ms = NULL;
len = ms->m_len - (4-i);
for (j=i; j<4; j++)
val |= (*dat++ << (8*j));