| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Linus Torvalds (pre-git) | 1586 | 59.38% | 7 | 10.77% |
| Jiri Slaby | 373 | 13.96% | 17 | 26.15% |
| Paul Fulghum | 267 | 10.00% | 6 | 9.23% |
| Alexander Popov | 212 | 7.94% | 1 | 1.54% |
| Arnaldo Carvalho de Melo | 85 | 3.18% | 1 | 1.54% |
| Alan Cox | 62 | 2.32% | 6 | 9.23% |
| Linus Torvalds | 20 | 0.75% | 6 | 9.23% |
| Ilya Zykov | 12 | 0.45% | 1 | 1.54% |
| Andrew Morton | 11 | 0.41% | 3 | 4.62% |
| Gustavo A. R. Silva | 10 | 0.37% | 2 | 3.08% |
| Dmitry Safonov | 10 | 0.37% | 1 | 1.54% |
| Al Viro | 8 | 0.30% | 5 | 7.69% |
| Jesper Juhl | 6 | 0.22% | 1 | 1.54% |
| Brian Bloniarz | 2 | 0.07% | 1 | 1.54% |
| Adrian Bunk | 1 | 0.04% | 1 | 1.54% |
| Nadia Yvette Chambers | 1 | 0.04% | 1 | 1.54% |
| Rusty Russell | 1 | 0.04% | 1 | 1.54% |
| Greg Kroah-Hartman | 1 | 0.04% | 1 | 1.54% |
| Michael Hayes | 1 | 0.04% | 1 | 1.54% |
| Alexey Dobriyan | 1 | 0.04% | 1 | 1.54% |
| Fabian Frederick | 1 | 0.04% | 1 | 1.54% |
| Total | 2671 | 65 |
// SPDX-License-Identifier: GPL-1.0+ /* generic HDLC line discipline for Linux * * Written by Paul Fulghum paulkf@microgate.com * for Microgate Corporation * * Microgate and SyncLink are registered trademarks of Microgate Corporation * * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>, * Al Longyear <longyear@netcom.com>, * Paul Mackerras <Paul.Mackerras@cs.anu.edu.au> * * Original release 01/11/99 * * This module implements the tty line discipline N_HDLC for use with * tty device drivers that support bit-synchronous HDLC communications. * * All HDLC data is frame oriented which means: * * 1. tty write calls represent one complete transmit frame of data * The device driver should accept the complete frame or none of * the frame (busy) in the write method. Each write call should have * a byte count in the range of 2-65535 bytes (2 is min HDLC frame * with 1 addr byte and 1 ctrl byte). The max byte count of 65535 * should include any crc bytes required. For example, when using * CCITT CRC32, 4 crc bytes are required, so the maximum size frame * the application may transmit is limited to 65531 bytes. For CCITT * CRC16, the maximum application frame size would be 65533. * * * 2. receive callbacks from the device driver represents * one received frame. The device driver should bypass * the tty flip buffer and call the line discipline receive * callback directly to avoid fragmenting or concatenating * multiple frames into a single receive callback. * * The HDLC line discipline queues the receive frames in separate * buffers so complete receive frames can be returned by the * tty read calls. * * 3. tty read calls returns an entire frame of data or nothing. * * 4. all send and receive data is considered raw. No processing * or translation is performed by the line discipline, regardless * of the tty flags * * 5. When line discipline is queried for the amount of receive * data available (FIOC), 0 is returned if no data available, * otherwise the count of the next available frame is returned. * (instead of the sum of all received frame counts). * * These conventions allow the standard tty programming interface * to be used for synchronous HDLC applications when used with * this line discipline (or another line discipline that is frame * oriented such as N_PPP). * * The SyncLink driver (synclink.c) implements both asynchronous * (using standard line discipline N_TTY) and synchronous HDLC * (using N_HDLC) communications, with the latter using the above * conventions. * * This implementation is very basic and does not maintain * any statistics. The main point is to enforce the raw data * and frame orientation of HDLC communications. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. */ #define HDLC_MAGIC 0x239e #include <linux/module.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/sched.h> #include <linux/types.h> #include <linux/fcntl.h> #include <linux/interrupt.h> #include <linux/ptrace.h> #include <linux/poll.h> #include <linux/in.h> #include <linux/ioctl.h> #include <linux/slab.h> #include <linux/tty.h> #include <linux/errno.h> #include <linux/string.h> /* used in new tty drivers */ #include <linux/signal.h> /* used in new tty drivers */ #include <linux/if.h> #include <linux/bitops.h> #include <asm/termios.h> #include <linux/uaccess.h> /* * Buffers for individual HDLC frames */ #define MAX_HDLC_FRAME_SIZE 65535 #define DEFAULT_RX_BUF_COUNT 10 #define MAX_RX_BUF_COUNT 60 #define DEFAULT_TX_BUF_COUNT 3 struct n_hdlc_buf { struct list_head list_item; int count; char buf[]; }; struct n_hdlc_buf_list { struct list_head list; int count; spinlock_t spinlock; }; /** * struct n_hdlc - per device instance data structure * @magic - magic value for structure * @tbusy - reentrancy flag for tx wakeup code * @woke_up - tx wakeup needs to be run again as it was called while @tbusy * @tx_buf_list - list of pending transmit frame buffers * @rx_buf_list - list of received frame buffers * @tx_free_buf_list - list unused transmit frame buffers * @rx_free_buf_list - list unused received frame buffers */ struct n_hdlc { int magic; bool tbusy; bool woke_up; struct n_hdlc_buf_list tx_buf_list; struct n_hdlc_buf_list rx_buf_list; struct n_hdlc_buf_list tx_free_buf_list; struct n_hdlc_buf_list rx_free_buf_list; }; /* * HDLC buffer list manipulation functions */ static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, struct n_hdlc_buf *buf); static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, struct n_hdlc_buf *buf); static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list); /* Local functions */ static struct n_hdlc *n_hdlc_alloc(void); /* max frame size for memory allocations */ static int maxframe = 4096; static void flush_rx_queue(struct tty_struct *tty) { struct n_hdlc *n_hdlc = tty->disc_data; struct n_hdlc_buf *buf; while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list))) n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf); } static void flush_tx_queue(struct tty_struct *tty) { struct n_hdlc *n_hdlc = tty->disc_data; struct n_hdlc_buf *buf; while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list))) n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf); } static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list) { struct n_hdlc_buf *buf; do { buf = n_hdlc_buf_get(list); kfree(buf); } while (buf); } /** * n_hdlc_tty_close - line discipline close * @tty - pointer to tty info structure * * Called when the line discipline is changed to something * else, the tty is closed, or the tty detects a hangup. */ static void n_hdlc_tty_close(struct tty_struct *tty) { struct n_hdlc *n_hdlc = tty->disc_data; if (n_hdlc->magic != HDLC_MAGIC) { pr_warn("n_hdlc: trying to close unopened tty!\n"); return; } #if defined(TTY_NO_WRITE_SPLIT) clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags); #endif tty->disc_data = NULL; /* Ensure that the n_hdlcd process is not hanging on select()/poll() */ wake_up_interruptible(&tty->read_wait); wake_up_interruptible(&tty->write_wait); n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list); n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list); n_hdlc_free_buf_list(&n_hdlc->rx_buf_list); n_hdlc_free_buf_list(&n_hdlc->tx_buf_list); kfree(n_hdlc); } /* end of n_hdlc_tty_close() */ /** * n_hdlc_tty_open - called when line discipline changed to n_hdlc * @tty - pointer to tty info structure * * Returns 0 if success, otherwise error code */ static int n_hdlc_tty_open(struct tty_struct *tty) { struct n_hdlc *n_hdlc = tty->disc_data; pr_debug("%s() called (device=%s)\n", __func__, tty->name); /* There should not be an existing table for this slot. */ if (n_hdlc) { pr_err("%s: tty already associated!\n", __func__); return -EEXIST; } n_hdlc = n_hdlc_alloc(); if (!n_hdlc) { pr_err("%s: n_hdlc_alloc failed\n", __func__); return -ENFILE; } tty->disc_data = n_hdlc; tty->receive_room = 65536; /* change tty_io write() to not split large writes into 8K chunks */ set_bit(TTY_NO_WRITE_SPLIT, &tty->flags); /* flush receive data from driver */ tty_driver_flush_buffer(tty); return 0; } /* end of n_tty_hdlc_open() */ /** * n_hdlc_send_frames - send frames on pending send buffer list * @n_hdlc - pointer to ldisc instance data * @tty - pointer to tty instance data * * Send frames on pending send buffer list until the driver does not accept a * frame (busy) this function is called after adding a frame to the send buffer * list and by the tty wakeup callback. */ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) { register int actual; unsigned long flags; struct n_hdlc_buf *tbuf; check_again: spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); if (n_hdlc->tbusy) { n_hdlc->woke_up = true; spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); return; } n_hdlc->tbusy = true; n_hdlc->woke_up = false; spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); while (tbuf) { pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count); /* Send the next block of data to device */ set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); actual = tty->ops->write(tty, tbuf->buf, tbuf->count); /* rollback was possible and has been done */ if (actual == -ERESTARTSYS) { n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); break; } /* if transmit error, throw frame away by */ /* pretending it was accepted by driver */ if (actual < 0) actual = tbuf->count; if (actual == tbuf->count) { pr_debug("frame %p completed\n", tbuf); /* free current transmit buffer */ n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf); /* wait up sleeping writers */ wake_up_interruptible(&tty->write_wait); /* get next pending transmit buffer */ tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); } else { pr_debug("frame %p pending\n", tbuf); /* * the buffer was not accepted by driver, * return it back into tx queue */ n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); break; } } if (!tbuf) clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); /* Clear the re-entry flag */ spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); n_hdlc->tbusy = false; spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); if (n_hdlc->woke_up) goto check_again; } /* end of n_hdlc_send_frames() */ /** * n_hdlc_tty_wakeup - Callback for transmit wakeup * @tty - pointer to associated tty instance data * * Called when low level device driver can accept more send data. */ static void n_hdlc_tty_wakeup(struct tty_struct *tty) { struct n_hdlc *n_hdlc = tty->disc_data; n_hdlc_send_frames(n_hdlc, tty); } /* end of n_hdlc_tty_wakeup() */ /** * n_hdlc_tty_receive - Called by tty driver when receive data is available * @tty - pointer to tty instance data * @data - pointer to received data * @flags - pointer to flags for data * @count - count of received data in bytes * * Called by tty low level driver when receive data is available. Data is * interpreted as one HDLC frame. */ static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data, char *flags, int count) { register struct n_hdlc *n_hdlc = tty->disc_data; register struct n_hdlc_buf *buf; pr_debug("%s() called count=%d\n", __func__, count); /* verify line is using HDLC discipline */ if (n_hdlc->magic != HDLC_MAGIC) { pr_err("line not using HDLC discipline\n"); return; } if (count > maxframe) { pr_debug("rx count>maxframesize, data discarded\n"); return; } /* get a free HDLC buffer */ buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list); if (!buf) { /* * no buffers in free list, attempt to allocate another rx * buffer unless the maximum count has been reached */ if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT) buf = kmalloc(struct_size(buf, buf, maxframe), GFP_ATOMIC); } if (!buf) { pr_debug("no more rx buffers, data discarded\n"); return; } /* copy received data to HDLC buffer */ memcpy(buf->buf, data, count); buf->count = count; /* add HDLC buffer to list of received frames */ n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf); /* wake up any blocked reads and perform async signalling */ wake_up_interruptible(&tty->read_wait); if (tty->fasync != NULL) kill_fasync(&tty->fasync, SIGIO, POLL_IN); } /* end of n_hdlc_tty_receive() */ /** * n_hdlc_tty_read - Called to retrieve one frame of data (if available) * @tty - pointer to tty instance data * @file - pointer to open file object * @buf - pointer to returned data buffer * @nr - size of returned data buffer * * Returns the number of bytes returned or error code. */ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, __u8 __user *buf, size_t nr) { struct n_hdlc *n_hdlc = tty->disc_data; int ret = 0; struct n_hdlc_buf *rbuf; DECLARE_WAITQUEUE(wait, current); /* verify user access to buffer */ if (!access_ok(buf, nr)) { pr_warn("%s(%d) %s() can't verify user buffer\n", __FILE__, __LINE__, __func__); return -EFAULT; } add_wait_queue(&tty->read_wait, &wait); for (;;) { if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { ret = -EIO; break; } if (tty_hung_up_p(file)) break; set_current_state(TASK_INTERRUPTIBLE); rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list); if (rbuf) { if (rbuf->count > nr) { /* too large for caller's buffer */ ret = -EOVERFLOW; } else { __set_current_state(TASK_RUNNING); if (copy_to_user(buf, rbuf->buf, rbuf->count)) ret = -EFAULT; else ret = rbuf->count; } if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT) kfree(rbuf); else n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf); break; } /* no data */ if (tty_io_nonblock(tty, file)) { ret = -EAGAIN; break; } schedule(); if (signal_pending(current)) { ret = -EINTR; break; } } remove_wait_queue(&tty->read_wait, &wait); __set_current_state(TASK_RUNNING); return ret; } /* end of n_hdlc_tty_read() */ /** * n_hdlc_tty_write - write a single frame of data to device * @tty - pointer to associated tty device instance data * @file - pointer to file object data * @data - pointer to transmit data (one frame) * @count - size of transmit frame in bytes * * Returns the number of bytes written (or error code). */ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, const unsigned char *data, size_t count) { struct n_hdlc *n_hdlc = tty->disc_data; int error = 0; DECLARE_WAITQUEUE(wait, current); struct n_hdlc_buf *tbuf; pr_debug("%s() called count=%zd\n", __func__, count); if (n_hdlc->magic != HDLC_MAGIC) return -EIO; /* verify frame size */ if (count > maxframe) { pr_debug("%s: truncating user packet from %zu to %d\n", __func__, count, maxframe); count = maxframe; } add_wait_queue(&tty->write_wait, &wait); for (;;) { set_current_state(TASK_INTERRUPTIBLE); tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list); if (tbuf) break; if (tty_io_nonblock(tty, file)) { error = -EAGAIN; break; } schedule(); if (signal_pending(current)) { error = -EINTR; break; } } __set_current_state(TASK_RUNNING); remove_wait_queue(&tty->write_wait, &wait); if (!error) { /* Retrieve the user's buffer */ memcpy(tbuf->buf, data, count); /* Send the data */ tbuf->count = error = count; n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf); n_hdlc_send_frames(n_hdlc, tty); } return error; } /* end of n_hdlc_tty_write() */ /** * n_hdlc_tty_ioctl - process IOCTL system call for the tty device. * @tty - pointer to tty instance data * @file - pointer to open file object for device * @cmd - IOCTL command code * @arg - argument for IOCTL call (cmd dependent) * * Returns command dependent result. */ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg) { struct n_hdlc *n_hdlc = tty->disc_data; int error = 0; int count; unsigned long flags; struct n_hdlc_buf *buf = NULL; pr_debug("%s() called %d\n", __func__, cmd); /* Verify the status of the device */ if (n_hdlc->magic != HDLC_MAGIC) return -EBADF; switch (cmd) { case FIONREAD: /* report count of read data available */ /* in next available frame (if any) */ spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags); buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list, struct n_hdlc_buf, list_item); if (buf) count = buf->count; else count = 0; spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags); error = put_user(count, (int __user *)arg); break; case TIOCOUTQ: /* get the pending tx byte count in the driver */ count = tty_chars_in_buffer(tty); /* add size of next output frame in queue */ spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list, struct n_hdlc_buf, list_item); if (buf) count += buf->count; spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); error = put_user(count, (int __user *)arg); break; case TCFLSH: switch (arg) { case TCIOFLUSH: case TCOFLUSH: flush_tx_queue(tty); } /* fall through - to default */ default: error = n_tty_ioctl_helper(tty, file, cmd, arg); break; } return error; } /* end of n_hdlc_tty_ioctl() */ /** * n_hdlc_tty_poll - TTY callback for poll system call * @tty - pointer to tty instance data * @filp - pointer to open file object for device * @poll_table - wait queue for operations * * Determine which operations (read/write) will not block and return info * to caller. * Returns a bit mask containing info on which ops will not block. */ static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, poll_table *wait) { struct n_hdlc *n_hdlc = tty->disc_data; __poll_t mask = 0; if (n_hdlc->magic != HDLC_MAGIC) return 0; /* * queue the current process into any wait queue that may awaken in the * future (read and write) */ poll_wait(filp, &tty->read_wait, wait); poll_wait(filp, &tty->write_wait, wait); /* set bits for operations that won't block */ if (!list_empty(&n_hdlc->rx_buf_list.list)) mask |= EPOLLIN | EPOLLRDNORM; /* readable */ if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) mask |= EPOLLHUP; if (tty_hung_up_p(filp)) mask |= EPOLLHUP; if (!tty_is_writelocked(tty) && !list_empty(&n_hdlc->tx_free_buf_list.list)) mask |= EPOLLOUT | EPOLLWRNORM; /* writable */ return mask; } /* end of n_hdlc_tty_poll() */ static void n_hdlc_alloc_buf(struct n_hdlc_buf_list *list, unsigned int count, const char *name) { struct n_hdlc_buf *buf; unsigned int i; for (i = 0; i < count; i++) { buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL); if (!buf) { pr_debug("%s(), kmalloc() failed for %s buffer %u\n", __func__, name, i); return; } n_hdlc_buf_put(list, buf); } } /** * n_hdlc_alloc - allocate an n_hdlc instance data structure * * Returns a pointer to newly created structure if success, otherwise %NULL */ static struct n_hdlc *n_hdlc_alloc(void) { struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL); if (!n_hdlc) return NULL; spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock); spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock); spin_lock_init(&n_hdlc->rx_buf_list.spinlock); spin_lock_init(&n_hdlc->tx_buf_list.spinlock); INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list); INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list); INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list); INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list); n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx"); n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx"); /* Initialize the control block */ n_hdlc->magic = HDLC_MAGIC; return n_hdlc; } /* end of n_hdlc_alloc() */ /** * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list * @buf_list - pointer to the buffer list * @buf - pointer to the buffer */ static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, struct n_hdlc_buf *buf) { unsigned long flags; spin_lock_irqsave(&buf_list->spinlock, flags); list_add(&buf->list_item, &buf_list->list); buf_list->count++; spin_unlock_irqrestore(&buf_list->spinlock, flags); } /** * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list * @buf_list - pointer to buffer list * @buf - pointer to buffer */ static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list, struct n_hdlc_buf *buf) { unsigned long flags; spin_lock_irqsave(&buf_list->spinlock, flags); list_add_tail(&buf->list_item, &buf_list->list); buf_list->count++; spin_unlock_irqrestore(&buf_list->spinlock, flags); } /* end of n_hdlc_buf_put() */ /** * n_hdlc_buf_get - remove and return an HDLC buffer from list * @buf_list - pointer to HDLC buffer list * * Remove and return an HDLC buffer from the head of the specified HDLC buffer * list. * Returns a pointer to HDLC buffer if available, otherwise %NULL. */ static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list) { unsigned long flags; struct n_hdlc_buf *buf; spin_lock_irqsave(&buf_list->spinlock, flags); buf = list_first_entry_or_null(&buf_list->list, struct n_hdlc_buf, list_item); if (buf) { list_del(&buf->list_item); buf_list->count--; } spin_unlock_irqrestore(&buf_list->spinlock, flags); return buf; } /* end of n_hdlc_buf_get() */ static struct tty_ldisc_ops n_hdlc_ldisc = { .owner = THIS_MODULE, .magic = TTY_LDISC_MAGIC, .name = "hdlc", .open = n_hdlc_tty_open, .close = n_hdlc_tty_close, .read = n_hdlc_tty_read, .write = n_hdlc_tty_write, .ioctl = n_hdlc_tty_ioctl, .poll = n_hdlc_tty_poll, .receive_buf = n_hdlc_tty_receive, .write_wakeup = n_hdlc_tty_wakeup, .flush_buffer = flush_rx_queue, }; static int __init n_hdlc_init(void) { int status; /* range check maxframe arg */ maxframe = clamp(maxframe, 4096, MAX_HDLC_FRAME_SIZE); status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc); if (!status) pr_info("N_HDLC line discipline registered with maxframe=%d\n", maxframe); else pr_err("N_HDLC: error registering line discipline: %d\n", status); return status; } /* end of init_module() */ static void __exit n_hdlc_exit(void) { /* Release tty registration of line discipline */ int status = tty_unregister_ldisc(N_HDLC); if (status) pr_err("N_HDLC: can't unregister line discipline (err = %d)\n", status); else pr_info("N_HDLC: line discipline unregistered\n"); } module_init(n_hdlc_init); module_exit(n_hdlc_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com"); module_param(maxframe, int, 0); MODULE_ALIAS_LDISC(N_HDLC);
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