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Make this driver work on the Alpha. Apparently the receive DMA mechanism 

has the same 4-byte alignment requirement that the transmit side does.  This
causes the packet payload to be misaligned.  So, on systems which require
strict alignment, we must copy the incoming frame to a new packet buffer,
suitably aligned.
This commit is contained in:
thorpej 1999-02-05 22:09:46 +00:00
parent 00007d07d6
commit d95d5b1488
1 changed files with 42 additions and 3 deletions
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45
sys/dev/pci/if_vr.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: if_vr.c,v 1.16 1999/02/05 21:20:31 thorpej Exp $ */
/* $NetBSD: if_vr.c,v 1.17 1999/02/05 22:09:46 thorpej Exp $ */
/*
* Copyright (c) 1997, 1998
@ -56,9 +56,14 @@
*
* The Rhine has a serious flaw in its transmit DMA mechanism:
* transmit buffers must be longword aligned. Unfortunately,
* FreeBSD doesn't guarantee that mbufs will be filled in starting
* the kernel doesn't guarantee that mbufs will be filled in starting
* at longword boundaries, so we have to do a buffer copy before
* transmission.
*
* Apparently, the receive DMA mechanism also has the same flaw. This
* means that on systems with struct alignment requirements, incoming
* frames must be copied to a new buffer which shifts the data forward
* 2 bytes so that the payload is aligned on a 4-byte boundary.
*/
#include "opt_inet.h"
@ -728,7 +733,6 @@ vr_rxeof(sc)
}
/* No errors; receive the packet. */
m = cur_rx->vr_mbuf;
total_len = VR_RXBYTES(cur_rx->vr_ptr->vr_status);
/*
@ -740,6 +744,7 @@ vr_rxeof(sc)
*/
total_len -= ETHER_CRC_LEN;
#ifdef __NO_STRICT_ALIGNMENT
/*
* Try to conjure up a new mbuf cluster. If that
* fails, it means we have an out of memory condition and
@ -747,12 +752,46 @@ vr_rxeof(sc)
* result in a lost packet, but there's little else we
* can do in this situation.
*/
m = cur_rx->vr_mbuf;
if (vr_newbuf(sc, cur_rx) == ENOBUFS) {
ifp->if_ierrors++;
cur_rx->vr_ptr->vr_status = VR_RXSTAT;
cur_rx->vr_ptr->vr_ctl = VR_RXCTL|VR_RXLEN;
continue;
}
#else
/*
* The Rhine's packet buffers must be 4-byte aligned.
* But this means that the data after the Ethernet header
* is misaligned. We must allocate a new buffer and
* copy the data, shifted forward 2 bytes.
*/
MGETHDR(m, M_DONTWAIT, MT_DATA);
if (m == NULL) {
dropit:
ifp->if_ierrors++;
cur_rx->vr_ptr->vr_status = VR_RXSTAT;
cur_rx->vr_ptr->vr_ctl = VR_RXCTL|VR_RXLEN;
continue;
}
if (total_len > (MHLEN - 2)) {
MCLGET(m, M_DONTWAIT);
if (m == NULL)
goto dropit;
}
m->m_data += 2;
/*
* Note that we use clusters for incoming frames, so the
* buffer is virtually contiguous.
*/
memcpy(mtod(m, caddr_t), mtod(cur_rx->vr_mbuf, caddr_t),
total_len);
/* Allow the recieve descriptor to continue using its mbuf. */
cur_rx->vr_ptr->vr_status = VR_RXSTAT;
cur_rx->vr_ptr->vr_ctl = VR_RXCTL|VR_RXLEN;
#endif /* __NO_STRICT_ALIGNMENT */
ifp->if_ipackets++;
eh = mtod(m, struct ether_header *);