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nuttx/drivers/net/slip.c
Xiang Xiao 2e54df0f35 Don't include assert.h from public header file 
Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
2021-06-03 08:36:03 -07:00

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/****************************************************************************
* drivers/net/slip.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/* Reference: RFC 1055 */
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/irq.h>
#include <nuttx/clock.h>
#include <nuttx/signal.h>
#include <nuttx/kthread.h>
#include <nuttx/semaphore.h>
#include <nuttx/fs/fs.h>
#include <nuttx/net/net.h>
#include <nuttx/net/netdev.h>
#include <nuttx/net/ip.h>
#include <nuttx/net/slip.h>
#if defined(CONFIG_NET) && defined(CONFIG_NET_SLIP)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* NOTE: Slip requires UART hardware handshake. If hardware handshake is
* not available with your UART, then you might try the 'slattach' option
* -L which enable "3-wire operation." That allows operation without the
* hardware handshake (but with the possibility of data overrun).
*/
/* Configuration ************************************************************/
#ifndef CONFIG_NET_SLIP_STACKSIZE
# define CONFIG_NET_SLIP_STACKSIZE 2048
#endif
#ifndef CONFIG_NET_SLIP_DEFPRIO
# define CONFIG_NET_SLIP_DEFPRIO 128
#endif
/* The Linux slip module hard-codes its MTU size to 296 (40 bytes for the
* IP+TCP headers plus 256 bytes of data). So you might as well set
* CONFIG_NET_SLIP_PKTSIZE to 296 as well.
*
* There may be an issue with this setting, however. I see that Linux uses
* a MTU of 296 and window of 256, but actually only sends 168 bytes of data:
* 40 + 128. I believe that is to allow for the 2x worst cast packet
* expansion. Ideally we would like to advertise the 256 MSS, but restrict
* transfers to 128 bytes (possibly by modifying the tcp_mss() macro).
*/
#if CONFIG_NET_SLIP_PKTSIZE < 296
# error "CONFIG_NET_SLIP_PKTSIZE >= 296 is required"
#endif
/* CONFIG_NET_SLIP_NINTERFACES determines the number of physical interfaces
* that will be supported.
*/
#ifndef CONFIG_NET_SLIP_NINTERFACES
# define CONFIG_NET_SLIP_NINTERFACES 1
#endif
/* SLIP special character codes ********************************************/
#define SLIP_END 0300 /* Indicates end of packet */
#define SLIP_ESC 0333 /* Indicates byte stuffing */
#define SLIP_ESC_END 0334 /* ESC ESC_END means SLIP_END data byte */
#define SLIP_ESC_ESC 0335 /* ESC ESC_ESC means ESC data byte */
/* General driver definitions ***********************************************/
/* TX poll delay = 1 second = 1000000 microseconds. */
#define SLIP_WDDELAY (1*1000000)
/* This is a helper pointer for accessing the contents of the ip header */
#define IPv4BUF ((FAR struct ipv4_hdr_s *)priv->dev.d_buf)
#define IPv6BUF ((FAR struct ipv6_hdr_s *)priv->dev.d_buf)
/****************************************************************************
* Private Types
****************************************************************************/
/* The slip_driver_s encapsulates all state information for a single hardware
* interface
*/
struct slip_driver_s
{
volatile bool bifup; /* true:ifup false:ifdown */
bool txnodelay; /* True: nxsig_usleep() not needed */
struct file file; /* TTY file descriptor */
uint16_t rxlen; /* The number of bytes in rxbuf */
pid_t rxpid; /* Receiver thread ID */
pid_t txpid; /* Transmitter thread ID */
sem_t waitsem; /* Mutually exclusive access to the network */
/* This holds the information visible to the NuttX network */
struct net_driver_s dev; /* Interface understood by the network */
uint8_t rxbuf[CONFIG_NET_SLIP_PKTSIZE + 2];
uint8_t txbuf[CONFIG_NET_SLIP_PKTSIZE + 2];
};
/****************************************************************************
* Private Data
****************************************************************************/
/* We really should get rid of CONFIG_NET_SLIP_NINTERFACES and, instead,
* kmm_malloc() new interface instances as needed.
*/
static struct slip_driver_s g_slip[CONFIG_NET_SLIP_NINTERFACES];
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static int slip_semtake(FAR struct slip_driver_s *priv);
static void slip_forcetake(FAR struct slip_driver_s *priv);
/* Common TX logic */
static void slip_write(FAR struct slip_driver_s *priv,
FAR const uint8_t *buffer, int len);
static void slip_putc(FAR struct slip_driver_s *priv, int ch);
static void slip_transmit(FAR struct slip_driver_s *priv);
static int slip_txpoll(FAR struct net_driver_s *dev);
static int slip_txtask(int argc, FAR char *argv[]);
/* Packet receiver task */
static int slip_getc(FAR struct slip_driver_s *priv);
static inline void slip_receive(FAR struct slip_driver_s *priv);
static int slip_rxtask(int argc, FAR char *argv[]);
/* NuttX callback functions */
static int slip_ifup(FAR struct net_driver_s *dev);
static int slip_ifdown(FAR struct net_driver_s *dev);
static int slip_txavail(FAR struct net_driver_s *dev);
#ifdef CONFIG_NET_MCASTGROUP
static int slip_addmac(FAR struct net_driver_s *dev, FAR const uint8_t *mac);
static int slip_rmmac(FAR struct net_driver_s *dev, FAR const uint8_t *mac);
#endif
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: slip_semtake
****************************************************************************/
static int slip_semtake(FAR struct slip_driver_s *priv)
{
return nxsem_wait_uninterruptible(&priv->waitsem);
}
#define slip_semgive(p) nxsem_post(&(p)->waitsem);
/****************************************************************************
* Name: slip_forcetake
*
* Description:
* This is just another wrapper but this one continues even if the thread
* is canceled. This must be done in certain conditions where were must
* continue in order to clean-up resources.
*
****************************************************************************/
static void slip_forcetake(FAR struct slip_driver_s *priv)
{
int ret;
do
{
ret = nxsem_wait_uninterruptible(&priv->waitsem);
/* The only expected error would -ECANCELED meaning that the
* parent thread has been canceled. We have to continue and
* terminate the poll in this case.
*/
DEBUGASSERT(ret == OK || ret == -ECANCELED);
}
while (ret < 0);
}
/****************************************************************************
* Name: slip_write
*
* Description:
* Just an inline wrapper around fwrite with error checking.
*
* Input Parameters:
* priv - Reference to the driver state structure
* buffer - Buffer data to send
* len - Buffer length in bytes
*
****************************************************************************/
static inline void slip_write(FAR struct slip_driver_s *priv,
FAR const uint8_t *buffer, int len)
{
/* Handle the case where the write is awakened by a signal */
while (file_write(&priv->file, buffer, len) < 0)
{
}
}
/****************************************************************************
* Name: slip_putc
*
* Description:
* Just an inline wrapper around putc with error checking.
*
* Input Parameters:
* priv - Reference to the driver state structure
* ch - The character to send
*
****************************************************************************/
static inline void slip_putc(FAR struct slip_driver_s *priv, int ch)
{
uint8_t buffer = (uint8_t)ch;
slip_write(priv, &buffer, 1);
}
/****************************************************************************
* Name: slip_transmit
*
* Description:
* Start hardware transmission. Called either from the txdone interrupt
* handling or from watchdog based polling.
*
* Input Parameters:
* priv - Reference to the driver state structure
*
* Returned Value:
* OK on success; a negated errno on failure
*
****************************************************************************/
static void slip_transmit(FAR struct slip_driver_s *priv)
{
uint8_t *src;
uint8_t *start;
uint8_t esc;
int remaining;
int len;
/* Increment statistics */
ninfo("Sending packet size %d\n", priv->dev.d_len);
NETDEV_TXPACKETS(&priv->dev);
/* Send an initial END character to flush out any data that may have
* accumulated in the receiver due to line noise
*/
slip_putc(priv, SLIP_END);
/* For each byte in the packet, send the appropriate character sequence */
src = priv->dev.d_buf;
remaining = priv->dev.d_len;
start = src;
len = 0;
while (remaining-- > 0)
{
switch (*src)
{
/* If it's the same code as an END character, we send a special two
* character code so as not to make the receiver think we sent an
* END
*/
case SLIP_END:
esc = SLIP_ESC_END;
goto escape;
/* If it's the same code as an ESC character, we send a special two
* character code so as not to make the receiver think we sent an
* ESC
*/
case SLIP_ESC:
esc = SLIP_ESC_ESC;
escape:
{
/* Flush any unsent data */
if (len > 0)
{
slip_write(priv, start, len);
}
/* Reset */
start = src + 1;
len = 0;
/* Then send the escape sequence */
slip_putc(priv, SLIP_ESC);
slip_putc(priv, esc);
}
break;
/* otherwise, just bump up the count */
default:
len++;
break;
}
/* Point to the next character in the packet */
src++;
}
/* We have looked at every character in the packet. Now flush any unsent
* data
*/
if (len > 0)
{
slip_write(priv, start, len);
}
/* And send the END token */
slip_putc(priv, SLIP_END);
NETDEV_TXDONE(&priv->dev);
priv->txnodelay = true;
}
/****************************************************************************
* Name: slip_txpoll
*
* Description:
* Check if the network has any outgoing packets ready to send. This is a
* callback from devif_poll(). devif_poll() may be called:
*
* 1. When the preceding TX packet send is complete, or
* 2. During normal periodic polling
*
* Input Parameters:
* dev - Reference to the NuttX driver state structure
*
* Returned Value:
* OK on success; a negated errno on failure
*
* Assumptions:
* The initiator of the poll holds the priv->waitsem;
*
****************************************************************************/
static int slip_txpoll(FAR struct net_driver_s *dev)
{
FAR struct slip_driver_s *priv =
(FAR struct slip_driver_s *)dev->d_private;
/* If the polling resulted in data that should be sent out on the network,
* the field d_len is set to a value > 0.
*/
if (priv->dev.d_len > 0)
{
if (!devif_loopback(&priv->dev))
{
slip_transmit(priv);
}
}
/* If zero is returned, the polling will continue until all connections
* have been examined.
*/
return 0;
}
/****************************************************************************
* Name: slip_txtask
*
* Description:
* Polling and transmission is performed on tx thread.
*
* Input Parameters:
* arg - Reference to the NuttX driver state structure
*
* Returned Value:
* None
*
****************************************************************************/
static int slip_txtask(int argc, FAR char *argv[])
{
FAR struct slip_driver_s *priv;
unsigned int index = *(argv[1]) - '0';
clock_t start_ticks;
clock_t now_ticks;
unsigned int hsec;
int ret;
nerr("index: %d\n", index);
DEBUGASSERT(index < CONFIG_NET_SLIP_NINTERFACES);
/* Get our private data structure instance and wake up the waiting
* initialization logic.
*/
priv = &g_slip[index];
slip_semgive(priv);
/* Loop forever */
start_ticks = clock_systime_ticks();
for (; ; )
{
/* Wait for the timeout to expire (or until we are signaled by */
ret = slip_semtake(priv);
if (ret < 0)
{
DEBUGASSERT(ret == -ECANCELED);
break;
}
if (!priv->txnodelay)
{
slip_semgive(priv);
nxsig_usleep(SLIP_WDDELAY);
}
else
{
priv->txnodelay = false;
slip_semgive(priv);
}
/* Is the interface up? */
if (priv->bifup)
{
/* Poll the networking layer for new XMIT data. */
net_lock();
priv->dev.d_buf = priv->txbuf;
/* Has a half second elapsed since the last timer poll? */
now_ticks = clock_systime_ticks();
hsec = (unsigned int)((now_ticks - start_ticks) / TICK_PER_HSEC);
if (hsec > 0)
{
/* Yes, perform the timer poll */
devif_timer(&priv->dev, hsec * TICK_PER_HSEC, slip_txpoll);
start_ticks += hsec * TICK_PER_HSEC;
}
else
{
/* No, perform the normal TX poll */
devif_timer(&priv->dev, 0, slip_txpoll);
}
net_unlock();
}
}
return OK;
}
/****************************************************************************
* Name: slip_getc
*
* Description:
* Get one byte from the serial input.
*
* Input Parameters:
* priv - Reference to the driver state structure
*
* Returned Value:
* The returned byte
*
****************************************************************************/
static inline int slip_getc(FAR struct slip_driver_s *priv)
{
uint8_t ch;
while (file_read(&priv->file, &ch, 1) < 0)
{
}
return ch;
}
/****************************************************************************
* Name: slip_receive
*
* Description:
* Read a packet from the serial input
*
* Input Parameters:
* priv - Reference to the driver state structure
*
* Returned Value:
* None
*
****************************************************************************/
static inline void slip_receive(FAR struct slip_driver_s *priv)
{
uint8_t ch;
/* Copy the data from the hardware to the RX buffer until we put
* together a whole packet. Make sure not to copy them into the
* packet if we run out of room.
*/
ninfo("Receiving packet\n");
for (; ; )
{
/* Get the next character in the stream. */
ch = slip_getc(priv);
/* Handle bytestuffing if necessary */
switch (ch)
{
/* If it's an END character then we're done with the packet.
* (OR we are just starting a packet)
*/
case SLIP_END:
{
ninfo("END\n");
/* A minor optimization: if there is no data in the packet,
* ignore it. This is meant to avoid bothering IP with all the
* empty packets generated by the duplicate END characters which
* are in turn sent to try to detect line noise.
*/
if (priv->rxlen > 0)
{
ninfo("Received packet size %d\n", priv->rxlen);
return;
}
}
break;
/* if it's the same code as an ESC character, wait and get another
* character and then figure out what to store in the packet based
* on that.
*/
case SLIP_ESC:
{
ninfo("ESC\n");
ch = slip_getc(priv);
/* if "ch" is not one of these two, then we have a protocol
* violation. The best bet seems to be to leave the byte alone
* and just stuff it into the packet
*/
switch (ch)
{
case SLIP_ESC_END:
ninfo("ESC-END\n");
ch = SLIP_END;
break;
case SLIP_ESC_ESC:
ninfo("ESC-ESC\n");
ch = SLIP_ESC;
break;
default:
nerr("ERROR: Protocol violation: %02x\n", ch);
break;
}
/* Here we fall into the default handler and let it store the
* character for us
*/
}
default:
{
if (priv->rxlen < CONFIG_NET_SLIP_PKTSIZE + 2)
{
priv->rxbuf[priv->rxlen++] = ch;
}
}
break;
}
}
}
/****************************************************************************
* Name: slip_rxtask
*
* Description:
* Wait for incoming data.
*
* Input Parameters:
* argc
* argv
*
* Returned Value:
* (Does not return)
*
* Assumptions:
*
****************************************************************************/
static int slip_rxtask(int argc, FAR char *argv[])
{
FAR struct slip_driver_s *priv;
unsigned int index = *(argv[1]) - '0';
int ch;
nerr("index: %d\n", index);
DEBUGASSERT(index < CONFIG_NET_SLIP_NINTERFACES);
/* Get our private data structure instance and wake up the waiting
* initialization logic.
*/
priv = &g_slip[index];
slip_semgive(priv);
/* Loop forever */
for (; ; )
{
/* Wait for the next character to be available on the input stream. */
ninfo("Waiting...\n");
ch = slip_getc(priv);
/* Ignore any input that we receive before the interface is up. */
if (!priv->bifup)
{
continue;
}
/* We have something...
*
* END characters may appear at packet boundaries BEFORE as well as
* after the beginning of the packet. This is normal and expected.
*/
if (ch == SLIP_END)
{
priv->rxlen = 0;
}
/* Otherwise, we are in danger of being out-of-sync. Apparently the
* leading END character is optional. Let's try to continue.
*/
else
{
priv->rxbuf[0] = (uint8_t)ch;
priv->rxlen = 1;
}
/* Copy the data data from the hardware to priv->rxbuf until we put
* together a whole packet.
*/
slip_receive(priv);
/* Handle the IP input. Get exclusive access to the network. */
net_lock();
priv->dev.d_buf = priv->rxbuf;
priv->dev.d_len = priv->rxlen;
NETDEV_RXPACKETS(&priv->dev);
/* All packets are assumed to be IP packets (we don't have a choice..
* there is no Ethernet header containing the EtherType). So pass the
* received packet on for IP processing -- but only if it is big
* enough to hold an IP header.
*/
#ifdef CONFIG_NET_IPv4
if ((IPv4BUF->vhl & IP_VERSION_MASK) == IPv4_VERSION)
{
NETDEV_RXIPV4(&priv->dev);
ipv4_input(&priv->dev);
/* If the above function invocation resulted in data that should
* be sent out on the network, the field d_len will set to a
* value > 0. NOTE that we are transmitting using the RX buffer!
*/
if (priv->dev.d_len > 0)
{
slip_transmit(priv);
}
}
else
#endif
#ifdef CONFIG_NET_IPv6
if ((IPv6BUF->vtc & IP_VERSION_MASK) == IPv6_VERSION)
{
NETDEV_RXIPV6(&priv->dev);
ipv6_input(&priv->dev);
/* If the above function invocation resulted in data that should
* be sent out on the network, the field d_len will set to a
* value > 0. NOTE that we are transmitting using the RX buffer!
*/
if (priv->dev.d_len > 0)
{
slip_transmit(priv);
}
}
else
#endif
{
NETDEV_RXERRORS(&priv->dev);
}
net_unlock();
}
/* We won't get here */
return OK;
}
/****************************************************************************
* Name: slip_ifup
*
* Description:
* NuttX Callback: Bring up the Ethernet interface when an IP address is
* provided
*
* Input Parameters:
* dev - Reference to the NuttX driver state structure
*
* Returned Value:
* None
*
* Assumptions:
*
****************************************************************************/
static int slip_ifup(FAR struct net_driver_s *dev)
{
FAR struct slip_driver_s *priv =
(FAR struct slip_driver_s *)dev->d_private;
#ifdef CONFIG_NET_IPv4
nerr("Bringing up: %d.%d.%d.%d\n",
dev->d_ipaddr & 0xff, (dev->d_ipaddr >> 8) & 0xff,
(dev->d_ipaddr >> 16) & 0xff, dev->d_ipaddr >> 24);
#endif
#ifdef CONFIG_NET_IPv6
ninfo("Bringing up: %04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x\n",
dev->d_ipv6addr[0], dev->d_ipv6addr[1], dev->d_ipv6addr[2],
dev->d_ipv6addr[3], dev->d_ipv6addr[4], dev->d_ipv6addr[5],
dev->d_ipv6addr[6], dev->d_ipv6addr[7]);
#endif
/* Mark the interface up */
priv->bifup = true;
return OK;
}
/****************************************************************************
* Name: slip_ifdown
*
* Description:
* NuttX Callback: Stop the interface.
*
* Input Parameters:
* dev - Reference to the NuttX driver state structure
*
* Returned Value:
* None
*
* Assumptions:
*
****************************************************************************/
static int slip_ifdown(FAR struct net_driver_s *dev)
{
FAR struct slip_driver_s *priv =
(FAR struct slip_driver_s *)dev->d_private;
/* Mark the device "down" */
priv->bifup = false;
return OK;
}
/****************************************************************************
* Name: slip_txavail
*
* Description:
* Driver callback invoked when new TX data is available. This is a
* stimulus perform an out-of-cycle poll and, thereby, reduce the TX
* latency.
*
* Input Parameters:
* dev - Reference to the NuttX driver state structure
*
* Returned Value:
* None
*
****************************************************************************/
static int slip_txavail(FAR struct net_driver_s *dev)
{
FAR struct slip_driver_s *priv =
(FAR struct slip_driver_s *)dev->d_private;
/* Ignore the notification if the interface is not yet up */
if (priv->bifup)
{
/* Wake up the TX polling thread */
priv->txnodelay = true;
nxsig_kill(priv->txpid, SIGALRM);
}
return OK;
}
/****************************************************************************
* Name: slip_addmac
*
* Description:
* NuttX Callback: Add the specified MAC address to the hardware multicast
* address filtering
*
* Input Parameters:
* dev - Reference to the NuttX driver state structure
* mac - The MAC address to be added
*
* Returned Value:
* None
*
* Assumptions:
*
****************************************************************************/
#ifdef CONFIG_NET_MCASTGROUP
static int slip_addmac(FAR struct net_driver_s *dev, FAR const uint8_t *mac)
{
FAR struct slip_driver_s *priv =
(FAR struct slip_driver_s *)dev->d_private;
/* Add the MAC address to the hardware multicast routing table */
return OK;
}
#endif
/****************************************************************************
* Name: slip_rmmac
*
* Description:
* NuttX Callback: Remove the specified MAC address from the hardware
* multicast address filtering
*
* Input Parameters:
* dev - Reference to the NuttX driver state structure
* mac - The MAC address to be removed
*
* Returned Value:
* None
*
* Assumptions:
*
****************************************************************************/
#ifdef CONFIG_NET_MCASTGROUP
static int slip_rmmac(FAR struct net_driver_s *dev, FAR const uint8_t *mac)
{
FAR struct slip_driver_s *priv =
(FAR struct slip_driver_s *)dev->d_private;
/* Add the MAC address to the hardware multicast routing table */
return OK;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: slip_initialize
*
* Description:
* Instantiate a SLIP network interface.
*
* Input Parameters:
* intf - In the case where there are multiple SLIP interfaces, this
* value identifies which is to be initialized. The number of
* possible SLIP interfaces is determined by
* devname - This is the path to the serial device that will support SLIP.
* For example, this might be "/dev/ttyS1"
*
* Returned Value:
* OK on success; Negated errno on failure.
*
* Assumptions:
*
****************************************************************************/
int slip_initialize(int intf, FAR const char *devname)
{
FAR struct slip_driver_s *priv;
char buffer[8];
FAR char *argv[2];
int ret;
/* Get the interface structure associated with this interface number. */
DEBUGASSERT(intf < CONFIG_NET_SLIP_NINTERFACES);
priv = &g_slip[intf];
/* Initialize the driver structure */
memset(priv, 0, sizeof(struct slip_driver_s));
priv->dev.d_ifup = slip_ifup; /* I/F up (new IP address) callback */
priv->dev.d_ifdown = slip_ifdown; /* I/F down callback */
priv->dev.d_txavail = slip_txavail; /* New TX data callback */
#ifdef CONFIG_NET_MCASTGROUP
priv->dev.d_addmac = slip_addmac; /* Add multicast MAC address */
priv->dev.d_rmmac = slip_rmmac; /* Remove multicast MAC address */
#endif
priv->dev.d_private = priv; /* Used to recover private state from dev */
/* Open the device */
ret = file_open(&priv->file, devname, O_RDWR, 0666);
if (ret < 0)
{
nerr("ERROR: Failed to open %s: %d\n", devname, ret);
return ret;
}
/* Initialize the wait semaphore */
nxsem_init(&priv->waitsem, 0, 0);
nxsem_set_protocol(&priv->waitsem, SEM_PRIO_NONE);
/* Start the SLIP receiver kernel thread */
snprintf(buffer, 8, "%d", intf);
argv[0] = buffer;
argv[1] = NULL;
priv->rxpid = kthread_create("rxslip", CONFIG_NET_SLIP_DEFPRIO,
CONFIG_NET_SLIP_STACKSIZE, slip_rxtask,
(FAR char * const *)argv);
if (priv->rxpid < 0)
{
nerr("ERROR: Failed to start receiver task\n");
return priv->rxpid;
}
/* Wait and make sure that the receive task is started. */
slip_forcetake(priv);
/* Start the SLIP transmitter kernel thread */
priv->txpid = kthread_create("txslip", CONFIG_NET_SLIP_DEFPRIO,
CONFIG_NET_SLIP_STACKSIZE, slip_txtask,
(FAR char * const *)argv);
if (priv->txpid < 0)
{
nerr("ERROR: Failed to start receiver task\n");
return priv->txpid;
}
/* Wait and make sure that the transmit task is started. */
slip_forcetake(priv);
/* Bump the semaphore count so that it can now be used as a mutex */
slip_semgive(priv);
/* Register the device with the OS so that socket IOCTLs can be performed */
netdev_register(&priv->dev, NET_LL_SLIP);
return OK;
}
#endif /* CONFIG_NET && CONFIG_NET_SLIP */
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