525 lines
11 KiB
C
525 lines
11 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Management Component Transport Protocol (MCTP) - serial transport
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* binding. This driver is an implementation of the DMTF specificiation
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* "DSP0253 - Management Component Transport Protocol (MCTP) Serial Transport
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* Binding", available at:
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*
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* https://www.dmtf.org/sites/default/files/standards/documents/DSP0253_1.0.0.pdf
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*
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* This driver provides DSP0253-type MCTP-over-serial transport using a Linux
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* tty device, by setting the N_MCTP line discipline on the tty.
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*
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* Copyright (c) 2021 Code Construct
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*/
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#include <linux/idr.h>
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#include <linux/if_arp.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/tty.h>
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#include <linux/workqueue.h>
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#include <linux/crc-ccitt.h>
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#include <linux/mctp.h>
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#include <net/mctp.h>
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#include <net/pkt_sched.h>
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#define MCTP_SERIAL_MTU 68 /* base mtu (64) + mctp header */
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#define MCTP_SERIAL_FRAME_MTU (MCTP_SERIAL_MTU + 6) /* + serial framing */
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#define MCTP_SERIAL_VERSION 0x1 /* DSP0253 defines a single version: 1 */
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#define BUFSIZE MCTP_SERIAL_FRAME_MTU
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#define BYTE_FRAME 0x7e
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#define BYTE_ESC 0x7d
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#define FCS_INIT 0xffff
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static DEFINE_IDA(mctp_serial_ida);
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enum mctp_serial_state {
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STATE_IDLE,
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STATE_START,
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STATE_HEADER,
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STATE_DATA,
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STATE_ESCAPE,
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STATE_TRAILER,
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STATE_DONE,
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STATE_ERR,
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};
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struct mctp_serial {
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struct net_device *netdev;
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struct tty_struct *tty;
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int idx;
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/* protects our rx & tx state machines; held during both paths */
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spinlock_t lock;
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struct work_struct tx_work;
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enum mctp_serial_state txstate, rxstate;
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u16 txfcs, rxfcs, rxfcs_rcvd;
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unsigned int txlen, rxlen;
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unsigned int txpos, rxpos;
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unsigned char txbuf[BUFSIZE],
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rxbuf[BUFSIZE];
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};
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static bool needs_escape(unsigned char c)
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{
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return c == BYTE_ESC || c == BYTE_FRAME;
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}
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static int next_chunk_len(struct mctp_serial *dev)
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{
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int i;
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/* either we have no bytes to send ... */
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if (dev->txpos == dev->txlen)
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return 0;
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/* ... or the next byte to send is an escaped byte; requiring a
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* single-byte chunk...
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*/
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if (needs_escape(dev->txbuf[dev->txpos]))
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return 1;
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/* ... or we have one or more bytes up to the next escape - this chunk
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* will be those non-escaped bytes, and does not include the escaped
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* byte.
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*/
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for (i = 1; i + dev->txpos + 1 < dev->txlen; i++) {
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if (needs_escape(dev->txbuf[dev->txpos + i + 1]))
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break;
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}
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return i;
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}
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static int write_chunk(struct mctp_serial *dev, unsigned char *buf, int len)
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{
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return dev->tty->ops->write(dev->tty, buf, len);
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}
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static void mctp_serial_tx_work(struct work_struct *work)
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{
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struct mctp_serial *dev = container_of(work, struct mctp_serial,
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tx_work);
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unsigned char c, buf[3];
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unsigned long flags;
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int len, txlen;
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spin_lock_irqsave(&dev->lock, flags);
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/* txstate represents the next thing to send */
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switch (dev->txstate) {
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case STATE_START:
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dev->txpos = 0;
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fallthrough;
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case STATE_HEADER:
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buf[0] = BYTE_FRAME;
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buf[1] = MCTP_SERIAL_VERSION;
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buf[2] = dev->txlen;
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if (!dev->txpos)
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dev->txfcs = crc_ccitt(FCS_INIT, buf + 1, 2);
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txlen = write_chunk(dev, buf + dev->txpos, 3 - dev->txpos);
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if (txlen <= 0) {
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dev->txstate = STATE_ERR;
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} else {
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dev->txpos += txlen;
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if (dev->txpos == 3) {
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dev->txstate = STATE_DATA;
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dev->txpos = 0;
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}
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}
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break;
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case STATE_ESCAPE:
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buf[0] = dev->txbuf[dev->txpos] & ~0x20;
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txlen = write_chunk(dev, buf, 1);
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if (txlen <= 0) {
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dev->txstate = STATE_ERR;
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} else {
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dev->txpos += txlen;
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if (dev->txpos == dev->txlen) {
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dev->txstate = STATE_TRAILER;
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dev->txpos = 0;
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}
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}
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break;
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case STATE_DATA:
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len = next_chunk_len(dev);
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if (len) {
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c = dev->txbuf[dev->txpos];
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if (len == 1 && needs_escape(c)) {
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buf[0] = BYTE_ESC;
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buf[1] = c & ~0x20;
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dev->txfcs = crc_ccitt_byte(dev->txfcs, c);
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txlen = write_chunk(dev, buf, 2);
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if (txlen == 2)
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dev->txpos++;
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else if (txlen == 1)
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dev->txstate = STATE_ESCAPE;
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else
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dev->txstate = STATE_ERR;
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} else {
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txlen = write_chunk(dev,
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dev->txbuf + dev->txpos,
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len);
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if (txlen <= 0) {
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dev->txstate = STATE_ERR;
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} else {
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dev->txfcs = crc_ccitt(dev->txfcs,
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dev->txbuf +
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dev->txpos,
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txlen);
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dev->txpos += txlen;
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}
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}
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if (dev->txstate == STATE_DATA &&
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dev->txpos == dev->txlen) {
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dev->txstate = STATE_TRAILER;
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dev->txpos = 0;
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}
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break;
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}
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dev->txstate = STATE_TRAILER;
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dev->txpos = 0;
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fallthrough;
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case STATE_TRAILER:
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buf[0] = dev->txfcs >> 8;
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buf[1] = dev->txfcs & 0xff;
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buf[2] = BYTE_FRAME;
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txlen = write_chunk(dev, buf + dev->txpos, 3 - dev->txpos);
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if (txlen <= 0) {
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dev->txstate = STATE_ERR;
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} else {
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dev->txpos += txlen;
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if (dev->txpos == 3) {
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dev->txstate = STATE_DONE;
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dev->txpos = 0;
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}
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}
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break;
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default:
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netdev_err_once(dev->netdev, "invalid tx state %d\n",
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dev->txstate);
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}
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if (dev->txstate == STATE_DONE) {
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dev->netdev->stats.tx_packets++;
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dev->netdev->stats.tx_bytes += dev->txlen;
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dev->txlen = 0;
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dev->txpos = 0;
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clear_bit(TTY_DO_WRITE_WAKEUP, &dev->tty->flags);
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dev->txstate = STATE_IDLE;
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spin_unlock_irqrestore(&dev->lock, flags);
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netif_wake_queue(dev->netdev);
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} else {
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spin_unlock_irqrestore(&dev->lock, flags);
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}
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}
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static netdev_tx_t mctp_serial_tx(struct sk_buff *skb, struct net_device *ndev)
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{
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struct mctp_serial *dev = netdev_priv(ndev);
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unsigned long flags;
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WARN_ON(dev->txstate != STATE_IDLE);
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if (skb->len > MCTP_SERIAL_MTU) {
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dev->netdev->stats.tx_dropped++;
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goto out;
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}
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spin_lock_irqsave(&dev->lock, flags);
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netif_stop_queue(dev->netdev);
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skb_copy_bits(skb, 0, dev->txbuf, skb->len);
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dev->txpos = 0;
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dev->txlen = skb->len;
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dev->txstate = STATE_START;
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spin_unlock_irqrestore(&dev->lock, flags);
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set_bit(TTY_DO_WRITE_WAKEUP, &dev->tty->flags);
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schedule_work(&dev->tx_work);
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out:
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kfree_skb(skb);
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return NETDEV_TX_OK;
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}
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static void mctp_serial_tty_write_wakeup(struct tty_struct *tty)
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{
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struct mctp_serial *dev = tty->disc_data;
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schedule_work(&dev->tx_work);
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}
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static void mctp_serial_rx(struct mctp_serial *dev)
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{
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struct mctp_skb_cb *cb;
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struct sk_buff *skb;
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if (dev->rxfcs != dev->rxfcs_rcvd) {
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dev->netdev->stats.rx_dropped++;
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dev->netdev->stats.rx_crc_errors++;
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return;
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}
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skb = netdev_alloc_skb(dev->netdev, dev->rxlen);
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if (!skb) {
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dev->netdev->stats.rx_dropped++;
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return;
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}
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skb->protocol = htons(ETH_P_MCTP);
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skb_put_data(skb, dev->rxbuf, dev->rxlen);
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skb_reset_network_header(skb);
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cb = __mctp_cb(skb);
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cb->halen = 0;
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netif_rx(skb);
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dev->netdev->stats.rx_packets++;
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dev->netdev->stats.rx_bytes += dev->rxlen;
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}
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static void mctp_serial_push_header(struct mctp_serial *dev, unsigned char c)
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{
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switch (dev->rxpos) {
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case 0:
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if (c == BYTE_FRAME)
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dev->rxpos++;
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else
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dev->rxstate = STATE_ERR;
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break;
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case 1:
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if (c == MCTP_SERIAL_VERSION) {
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dev->rxpos++;
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dev->rxfcs = crc_ccitt_byte(FCS_INIT, c);
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} else {
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dev->rxstate = STATE_ERR;
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}
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break;
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case 2:
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if (c > MCTP_SERIAL_FRAME_MTU) {
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dev->rxstate = STATE_ERR;
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} else {
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dev->rxlen = c;
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dev->rxpos = 0;
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dev->rxstate = STATE_DATA;
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dev->rxfcs = crc_ccitt_byte(dev->rxfcs, c);
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}
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break;
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}
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}
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static void mctp_serial_push_trailer(struct mctp_serial *dev, unsigned char c)
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{
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switch (dev->rxpos) {
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case 0:
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dev->rxfcs_rcvd = c << 8;
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dev->rxpos++;
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break;
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case 1:
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dev->rxfcs_rcvd |= c;
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dev->rxpos++;
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break;
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case 2:
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if (c != BYTE_FRAME) {
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dev->rxstate = STATE_ERR;
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} else {
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mctp_serial_rx(dev);
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dev->rxlen = 0;
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dev->rxpos = 0;
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dev->rxstate = STATE_IDLE;
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}
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break;
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}
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}
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static void mctp_serial_push(struct mctp_serial *dev, unsigned char c)
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{
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switch (dev->rxstate) {
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case STATE_IDLE:
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dev->rxstate = STATE_HEADER;
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fallthrough;
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case STATE_HEADER:
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mctp_serial_push_header(dev, c);
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break;
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case STATE_ESCAPE:
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c |= 0x20;
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fallthrough;
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case STATE_DATA:
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if (dev->rxstate != STATE_ESCAPE && c == BYTE_ESC) {
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dev->rxstate = STATE_ESCAPE;
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} else {
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dev->rxfcs = crc_ccitt_byte(dev->rxfcs, c);
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dev->rxbuf[dev->rxpos] = c;
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dev->rxpos++;
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dev->rxstate = STATE_DATA;
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if (dev->rxpos == dev->rxlen) {
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dev->rxpos = 0;
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dev->rxstate = STATE_TRAILER;
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}
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}
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break;
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case STATE_TRAILER:
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mctp_serial_push_trailer(dev, c);
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break;
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case STATE_ERR:
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if (c == BYTE_FRAME)
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dev->rxstate = STATE_IDLE;
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break;
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||
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|
default:
|
||
|
|
netdev_err_once(dev->netdev, "invalid rx state %d\n",
|
||
|
|
dev->rxstate);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
static void mctp_serial_tty_receive_buf(struct tty_struct *tty,
|
||
|
|
const unsigned char *c,
|
||
|
|
const char *f, int len)
|
||
|
|
{
|
||
|
|
struct mctp_serial *dev = tty->disc_data;
|
||
|
|
int i;
|
||
|
|
|
||
|
|
if (!netif_running(dev->netdev))
|
||
|
|
return;
|
||
|
|
|
||
|
|
/* we don't (currently) use the flag bytes, just data. */
|
||
|
|
for (i = 0; i < len; i++)
|
||
|
|
mctp_serial_push(dev, c[i]);
|
||
|
|
}
|
||
|
|
|
||
|
|
static void mctp_serial_uninit(struct net_device *ndev)
|
||
|
|
{
|
||
|
|
struct mctp_serial *dev = netdev_priv(ndev);
|
||
|
|
|
||
|
|
cancel_work_sync(&dev->tx_work);
|
||
|
|
}
|
||
|
|
|
||
|
|
static const struct net_device_ops mctp_serial_netdev_ops = {
|
||
|
|
.ndo_start_xmit = mctp_serial_tx,
|
||
|
|
.ndo_uninit = mctp_serial_uninit,
|
||
|
|
};
|
||
|
|
|
||
|
|
static void mctp_serial_setup(struct net_device *ndev)
|
||
|
|
{
|
||
|
|
ndev->type = ARPHRD_MCTP;
|
||
|
|
|
||
|
|
/* we limit at the fixed MTU, which is also the MCTP-standard
|
||
|
|
* baseline MTU, so is also our minimum
|
||
|
|
*/
|
||
|
|
ndev->mtu = MCTP_SERIAL_MTU;
|
||
|
|
ndev->max_mtu = MCTP_SERIAL_MTU;
|
||
|
|
ndev->min_mtu = MCTP_SERIAL_MTU;
|
||
|
|
|
||
|
|
ndev->hard_header_len = 0;
|
||
|
|
ndev->addr_len = 0;
|
||
|
|
ndev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
|
||
|
|
ndev->flags = IFF_NOARP;
|
||
|
|
ndev->netdev_ops = &mctp_serial_netdev_ops;
|
||
|
|
ndev->needs_free_netdev = true;
|
||
|
|
}
|
||
|
|
|
||
|
|
static int mctp_serial_open(struct tty_struct *tty)
|
||
|
|
{
|
||
|
|
struct mctp_serial *dev;
|
||
|
|
struct net_device *ndev;
|
||
|
|
char name[32];
|
||
|
|
int idx, rc;
|
||
|
|
|
||
|
|
if (!capable(CAP_NET_ADMIN))
|
||
|
|
return -EPERM;
|
||
|
|
|
||
|
|
if (!tty->ops->write)
|
||
|
|
return -EOPNOTSUPP;
|
||
|
|
|
||
|
|
idx = ida_alloc(&mctp_serial_ida, GFP_KERNEL);
|
||
|
|
if (idx < 0)
|
||
|
|
return idx;
|
||
|
|
|
||
|
|
snprintf(name, sizeof(name), "mctpserial%d", idx);
|
||
|
|
ndev = alloc_netdev(sizeof(*dev), name, NET_NAME_ENUM,
|
||
|
|
mctp_serial_setup);
|
||
|
|
if (!ndev) {
|
||
|
|
rc = -ENOMEM;
|
||
|
|
goto free_ida;
|
||
|
|
}
|
||
|
|
|
||
|
|
dev = netdev_priv(ndev);
|
||
|
|
dev->idx = idx;
|
||
|
|
dev->tty = tty;
|
||
|
|
dev->netdev = ndev;
|
||
|
|
dev->txstate = STATE_IDLE;
|
||
|
|
dev->rxstate = STATE_IDLE;
|
||
|
|
spin_lock_init(&dev->lock);
|
||
|
|
INIT_WORK(&dev->tx_work, mctp_serial_tx_work);
|
||
|
|
|
||
|
|
rc = register_netdev(ndev);
|
||
|
|
if (rc)
|
||
|
|
goto free_netdev;
|
||
|
|
|
||
|
|
tty->receive_room = 64 * 1024;
|
||
|
|
tty->disc_data = dev;
|
||
|
|
|
||
|
|
return 0;
|
||
|
|
|
||
|
|
free_netdev:
|
||
|
|
free_netdev(ndev);
|
||
|
|
|
||
|
|
free_ida:
|
||
|
|
ida_free(&mctp_serial_ida, idx);
|
||
|
|
return rc;
|
||
|
|
}
|
||
|
|
|
||
|
|
static void mctp_serial_close(struct tty_struct *tty)
|
||
|
|
{
|
||
|
|
struct mctp_serial *dev = tty->disc_data;
|
||
|
|
int idx = dev->idx;
|
||
|
|
|
||
|
|
unregister_netdev(dev->netdev);
|
||
|
|
ida_free(&mctp_serial_ida, idx);
|
||
|
|
}
|
||
|
|
|
||
|
|
static struct tty_ldisc_ops mctp_ldisc = {
|
||
|
|
.owner = THIS_MODULE,
|
||
|
|
.num = N_MCTP,
|
||
|
|
.name = "mctp",
|
||
|
|
.open = mctp_serial_open,
|
||
|
|
.close = mctp_serial_close,
|
||
|
|
.receive_buf = mctp_serial_tty_receive_buf,
|
||
|
|
.write_wakeup = mctp_serial_tty_write_wakeup,
|
||
|
|
};
|
||
|
|
|
||
|
|
static int __init mctp_serial_init(void)
|
||
|
|
{
|
||
|
|
return tty_register_ldisc(&mctp_ldisc);
|
||
|
|
}
|
||
|
|
|
||
|
|
static void __exit mctp_serial_exit(void)
|
||
|
|
{
|
||
|
|
tty_unregister_ldisc(&mctp_ldisc);
|
||
|
|
}
|
||
|
|
|
||
|
|
module_init(mctp_serial_init);
|
||
|
|
module_exit(mctp_serial_exit);
|
||
|
|
|
||
|
|
MODULE_LICENSE("GPL v2");
|
||
|
|
MODULE_AUTHOR("Jeremy Kerr <jk@codeconstruct.com.au>");
|
||
|
|
MODULE_DESCRIPTION("MCTP Serial transport");
|