From patchwork Mon Nov 22 04:28:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeremy Kerr X-Patchwork-Id: 12631219 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5DD2FC433F5 for ; Mon, 22 Nov 2021 04:28:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231684AbhKVEbc (ORCPT ); Sun, 21 Nov 2021 23:31:32 -0500 Received: from pi.codeconstruct.com.au ([203.29.241.158]:54950 "EHLO codeconstruct.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229870AbhKVEbb (ORCPT ); Sun, 21 Nov 2021 23:31:31 -0500 Received: by codeconstruct.com.au (Postfix, from userid 10000) id 479292022C; Mon, 22 Nov 2021 12:28:24 +0800 (AWST) From: Jeremy Kerr To: netdev@vger.kernel.org Cc: Matt Johnston , "David S. Miller" , Jakub Kicinski , Jiri Slaby , Greg Kroah-Hartman Subject: [PATCH net-next] mctp: Add MCTP-over-serial transport binding Date: Mon, 22 Nov 2021 12:28:17 +0800 Message-Id: <20211122042817.2988517-1-jk@codeconstruct.com.au> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org This change adds a MCTP Serial transport binding, as per DMTF DSP0253. This is implemented as a new serial line discipline, and can be attached to arbitrary serial devices. The 'mctp' utility provides the ldisc magic to set up the serial link: # mctp link serial /dev/ttyS0 & # mctp link dev lo index 1 address 0x00:00:00:00:00:00 net 1 mtu 65536 up dev mctpserial0 index 5 address 0x(no-addr) net 1 mtu 68 down Signed-off-by: Jeremy Kerr --- drivers/net/mctp/Kconfig | 11 + drivers/net/mctp/Makefile | 1 + drivers/net/mctp/mctp-serial.c | 494 +++++++++++++++++++++++++++++++++ include/uapi/linux/tty.h | 1 + 4 files changed, 507 insertions(+) create mode 100644 drivers/net/mctp/mctp-serial.c diff --git a/drivers/net/mctp/Kconfig b/drivers/net/mctp/Kconfig index d8f966cedc89..02f3c2d600fd 100644 --- a/drivers/net/mctp/Kconfig +++ b/drivers/net/mctp/Kconfig @@ -3,6 +3,17 @@ if MCTP menu "MCTP Device Drivers" +config MCTP_SERIAL + tristate "MCTP serial transport" + depends on TTY + select CRC_CCITT + help + This driver provides an MCTP-over-serial interface, through a + serial line-discipline. By attaching the ldisc to a serial device, + we get a new net device to transport MCTP packets. + + Say y here if you need to connect to MCTP devices over serial. + endmenu endif diff --git a/drivers/net/mctp/Makefile b/drivers/net/mctp/Makefile index e69de29bb2d1..d32622613ce4 100644 --- a/drivers/net/mctp/Makefile +++ b/drivers/net/mctp/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_MCTP_SERIAL) += mctp-serial.o diff --git a/drivers/net/mctp/mctp-serial.c b/drivers/net/mctp/mctp-serial.c new file mode 100644 index 000000000000..30950f1ea6f4 --- /dev/null +++ b/drivers/net/mctp/mctp-serial.c @@ -0,0 +1,494 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Management Component Transport Protocol (MCTP) - serial transport + * binding. + * + * Copyright (c) 2021 Code Construct + */ + +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include + +#define MCTP_SERIAL_MTU 68 /* base mtu (64) + mctp header */ +#define MCTP_SERIAL_FRAME_MTU (MCTP_SERIAL_MTU + 6) /* + serial framing */ + +#define MCTP_SERIAL_VERSION 0x1 + +#define BUFSIZE MCTP_SERIAL_FRAME_MTU + +#define BYTE_FRAME 0x7e +#define BYTE_ESC 0x7d + +static DEFINE_IDA(mctp_serial_ida); + +enum mctp_serial_state { + STATE_IDLE, + STATE_START, + STATE_HEADER, + STATE_DATA, + STATE_ESCAPE, + STATE_TRAILER, + STATE_DONE, + STATE_ERR, +}; + +struct mctp_serial { + struct net_device *netdev; + struct tty_struct *tty; + + int idx; + + /* protects our rx & tx state machines; held during both paths */ + spinlock_t lock; + + struct work_struct tx_work; + enum mctp_serial_state txstate, rxstate; + u16 txfcs, rxfcs, rxfcs_rcvd; + unsigned int txlen, rxlen; + unsigned int txpos, rxpos; + unsigned char txbuf[BUFSIZE], + rxbuf[BUFSIZE]; +}; + +static bool needs_escape(unsigned char c) +{ + return c == BYTE_ESC || c == BYTE_FRAME; +} + +static int next_chunk_len(struct mctp_serial *dev) +{ + int i; + + /* either we have no bytes to send ... */ + if (dev->txpos == dev->txlen) + return 0; + + /* ... or the next byte to send is an escaped byte; requiring a + * single-byte chunk... + */ + if (needs_escape(dev->txbuf[dev->txpos])) + return 1; + + /* ... or we have one or more bytes up to the next escape - this chunk + * will be those non-escaped bytes, and does not include the escaped + * byte. + */ + for (i = 1; i + dev->txpos + 1 < dev->txlen; i++) { + if (needs_escape(dev->txbuf[dev->txpos + i + 1])) + break; + } + + return i; +} + +static int write_chunk(struct mctp_serial *dev, unsigned char *buf, int len) +{ + return dev->tty->ops->write(dev->tty, buf, len); +} + +static void mctp_serial_tx_work(struct work_struct *work) +{ + struct mctp_serial *dev = container_of(work, struct mctp_serial, + tx_work); + unsigned char c, buf[3]; + unsigned long flags; + int len, txlen; + + spin_lock_irqsave(&dev->lock, flags); + + /* txstate represents the next thing to send */ + switch (dev->txstate) { + case STATE_START: + dev->txpos = 0; + fallthrough; + case STATE_HEADER: + buf[0] = BYTE_FRAME; + buf[1] = MCTP_SERIAL_VERSION; + buf[2] = dev->txlen; + + if (!dev->txpos) + dev->txfcs = crc_ccitt(0, buf + 1, 2); + + txlen = write_chunk(dev, buf + dev->txpos, 3 - dev->txpos); + if (txlen <= 0) { + dev->txstate = STATE_ERR; + } else { + dev->txpos += txlen; + if (dev->txpos == 3) { + dev->txstate = STATE_DATA; + dev->txpos = 0; + } + } + break; + + case STATE_ESCAPE: + buf[0] = dev->txbuf[dev->txpos] & ~0x20; + txlen = write_chunk(dev, buf, 1); + dev->txpos += txlen; + if (dev->txpos == dev->txlen) { + dev->txstate = STATE_TRAILER; + dev->txpos = 0; + } + + break; + + case STATE_DATA: + len = next_chunk_len(dev); + if (len) { + c = dev->txbuf[dev->txpos]; + if (len == 1 && needs_escape(c)) { + buf[0] = BYTE_ESC; + buf[1] = c & ~0x20; + dev->txfcs = crc_ccitt_byte(dev->txfcs, c); + txlen = write_chunk(dev, buf, 2); + if (txlen == 2) + dev->txpos++; + else if (txlen == 1) + dev->txstate = STATE_ESCAPE; + } else { + txlen = write_chunk(dev, + dev->txbuf + dev->txpos, + len); + dev->txfcs = crc_ccitt(dev->txfcs, + dev->txbuf + dev->txpos, + txlen); + dev->txpos += txlen; + } + if (dev->txstate == STATE_DATA && + dev->txpos == dev->txlen) { + dev->txstate = STATE_TRAILER; + dev->txpos = 0; + } + break; + } + dev->txstate = STATE_TRAILER; + fallthrough; + + case STATE_TRAILER: + buf[0] = dev->txfcs >> 8; + buf[1] = dev->txfcs & 0xff; + buf[2] = BYTE_FRAME; + txlen = write_chunk(dev, buf + dev->txpos, 3 - dev->txpos); + if (txlen <= 0) { + dev->txstate = STATE_ERR; + } else { + dev->txpos += txlen; + if (dev->txpos == 3) { + dev->txstate = STATE_DONE; + dev->txpos = 0; + } + } + break; + default: + netdev_err_once(dev->netdev, "invalid tx state %d\n", + dev->txstate); + } + + if (dev->txstate == STATE_DONE) { + dev->netdev->stats.tx_packets++; + dev->netdev->stats.tx_bytes += dev->txlen; + dev->txlen = 0; + dev->txpos = 0; + clear_bit(TTY_DO_WRITE_WAKEUP, &dev->tty->flags); + dev->txstate = STATE_IDLE; + spin_unlock_irqrestore(&dev->lock, flags); + + netif_wake_queue(dev->netdev); + } else { + spin_unlock_irqrestore(&dev->lock, flags); + } +} + +static netdev_tx_t mctp_serial_tx(struct sk_buff *skb, struct net_device *ndev) +{ + struct mctp_serial *dev = netdev_priv(ndev); + unsigned long flags; + + WARN_ON(dev->txstate != STATE_IDLE); + + if (skb->len > MCTP_SERIAL_MTU) { + dev->netdev->stats.tx_dropped++; + goto out; + } + + spin_lock_irqsave(&dev->lock, flags); + netif_stop_queue(dev->netdev); + skb_copy_bits(skb, 0, dev->txbuf, skb->len); + dev->txpos = 0; + dev->txlen = skb->len; + dev->txstate = STATE_START; + spin_unlock_irqrestore(&dev->lock, flags); + + set_bit(TTY_DO_WRITE_WAKEUP, &dev->tty->flags); + schedule_work(&dev->tx_work); + +out: + kfree_skb(skb); + return NETDEV_TX_OK; +} + +static void mctp_serial_tty_write_wakeup(struct tty_struct *tty) +{ + struct mctp_serial *dev; + + rcu_read_lock(); + dev = rcu_dereference(tty->disc_data); + schedule_work(&dev->tx_work); + rcu_read_unlock(); +} + +static void mctp_serial_rx(struct mctp_serial *dev) +{ + struct mctp_skb_cb *cb; + struct sk_buff *skb; + + if (dev->rxfcs != dev->rxfcs_rcvd) { + dev->netdev->stats.rx_dropped++; + dev->netdev->stats.rx_crc_errors++; + return; + } + + skb = netdev_alloc_skb(dev->netdev, dev->rxlen); + if (!skb) { + dev->netdev->stats.rx_dropped++; + return; + } + + skb->protocol = htons(ETH_P_MCTP); + skb_put_data(skb, dev->rxbuf, dev->rxlen); + skb_reset_network_header(skb); + + cb = __mctp_cb(skb); + cb->halen = 0; + + netif_rx_ni(skb); + dev->netdev->stats.rx_packets++; + dev->netdev->stats.rx_bytes += dev->rxlen; +} + +static void mctp_serial_push_header(struct mctp_serial *dev, unsigned char c) +{ + switch (dev->rxpos) { + case 0: + if (c == BYTE_FRAME) + dev->rxpos++; + else + dev->rxstate = STATE_ERR; + break; + case 1: + if (c == MCTP_SERIAL_VERSION) { + dev->rxpos++; + dev->rxfcs = crc_ccitt_byte(0, c); + } else { + dev->rxstate = STATE_ERR; + } + break; + case 2: + if (c > MCTP_SERIAL_FRAME_MTU) { + dev->rxstate = STATE_ERR; + } else { + dev->rxlen = c; + dev->rxpos = 0; + dev->rxstate = STATE_DATA; + dev->rxfcs = crc_ccitt_byte(dev->rxfcs, c); + } + break; + } +} + +static void mctp_serial_push_trailer(struct mctp_serial *dev, unsigned char c) +{ + switch (dev->rxpos) { + case 0: + dev->rxfcs_rcvd = c << 8; + dev->rxpos++; + break; + case 1: + dev->rxfcs_rcvd |= c; + dev->rxpos++; + break; + case 2: + if (c != BYTE_FRAME) { + dev->rxstate = STATE_ERR; + } else { + mctp_serial_rx(dev); + dev->rxlen = 0; + dev->rxpos = 0; + dev->rxstate = STATE_IDLE; + } + break; + } +} + +static void mctp_serial_push(struct mctp_serial *dev, unsigned char c) +{ + switch (dev->rxstate) { + case STATE_IDLE: + dev->rxstate = STATE_HEADER; + fallthrough; + case STATE_HEADER: + mctp_serial_push_header(dev, c); + break; + + case STATE_ESCAPE: + c |= 0x20; + fallthrough; + case STATE_DATA: + if (dev->rxstate != STATE_ESCAPE && c == BYTE_ESC) { + dev->rxstate = STATE_ESCAPE; + } else { + dev->rxfcs = crc_ccitt_byte(dev->rxfcs, c); + dev->rxbuf[dev->rxpos] = c; + dev->rxpos++; + dev->rxstate = STATE_DATA; + if (dev->rxpos == dev->rxlen) { + dev->rxpos = 0; + dev->rxstate = STATE_TRAILER; + } + } + break; + + case STATE_TRAILER: + mctp_serial_push_trailer(dev, c); + break; + + case STATE_ERR: + if (c == BYTE_FRAME) + dev->rxstate = STATE_IDLE; + break; + + 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 const struct net_device_ops mctp_serial_netdev_ops = { + .ndo_start_xmit = mctp_serial_tx, +}; + +static void mctp_serial_setup(struct net_device *ndev) +{ + ndev->type = ARPHRD_MCTP; + ndev->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; + + if (tty->disc_data) + return -EEXIST; + + 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 "); +MODULE_DESCRIPTION("MCTP Serial transport"); diff --git a/include/uapi/linux/tty.h b/include/uapi/linux/tty.h index 376cccf397be..a58deb3061eb 100644 --- a/include/uapi/linux/tty.h +++ b/include/uapi/linux/tty.h @@ -38,5 +38,6 @@ #define N_NCI 25 /* NFC NCI UART */ #define N_SPEAKUP 26 /* Speakup communication with synths */ #define N_NULL 27 /* Null ldisc used for error handling */ +#define N_MCTP 28 /* MCTP-over-serial */ #endif /* _UAPI_LINUX_TTY_H */