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Diffstat (limited to 'drivers/tty/n_hdlc.c')
| -rw-r--r-- | drivers/tty/n_hdlc.c | 828 |
1 files changed, 828 insertions, 0 deletions
diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c new file mode 100644 index 000000000..46b09bfb6 --- /dev/null +++ b/drivers/tty/n_hdlc.c @@ -0,0 +1,828 @@ +// 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. + */ + +#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 <linux/uaccess.h> +#include "tty.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 + * @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 { + 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; + struct work_struct write_work; + struct tty_struct *tty_for_write_work; +}; + +/* + * 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); +static void n_hdlc_tty_write_work(struct work_struct *work); + +/* 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 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); + + cancel_work_sync(&n_hdlc->write_work); + + 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; + } + + INIT_WORK(&n_hdlc->write_work, n_hdlc_tty_write_work); + n_hdlc->tty_for_write_work = tty; + 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_write_work - Asynchronous callback for transmit wakeup + * @work: pointer to work_struct + * + * Called when low level device driver can accept more send data. + */ +static void n_hdlc_tty_write_work(struct work_struct *work) +{ + struct n_hdlc *n_hdlc = container_of(work, struct n_hdlc, write_work); + struct tty_struct *tty = n_hdlc->tty_for_write_work; + + n_hdlc_send_frames(n_hdlc, tty); +} /* end of n_hdlc_tty_write_work() */ + +/** + * 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; + + schedule_work(&n_hdlc->write_work); +} /* 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, + const 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); + + 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 + * @kbuf: pointer to returned data buffer + * @nr: size of returned data buffer + * @cookie: stored rbuf from previous run + * @offset: offset into the 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 *kbuf, size_t nr, + void **cookie, unsigned long offset) +{ + struct n_hdlc *n_hdlc = tty->disc_data; + int ret = 0; + struct n_hdlc_buf *rbuf; + DECLARE_WAITQUEUE(wait, current); + + /* Is this a repeated call for an rbuf we already found earlier? */ + rbuf = *cookie; + if (rbuf) + goto have_rbuf; + + 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) + 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); + + if (!rbuf) + return ret; + *cookie = rbuf; + +have_rbuf: + /* Have we used it up entirely? */ + if (offset >= rbuf->count) + goto done_with_rbuf; + + /* More data to go, but can't copy any more? EOVERFLOW */ + ret = -EOVERFLOW; + if (!nr) + goto done_with_rbuf; + + /* Copy as much data as possible */ + ret = rbuf->count - offset; + if (ret > nr) + ret = nr; + memcpy(kbuf, rbuf->buf+offset, ret); + offset += ret; + + /* If we still have data left, we leave the rbuf in the cookie */ + if (offset < rbuf->count) + return ret; + +done_with_rbuf: + *cookie = NULL; + + 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); + + 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); + + /* 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 + * @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, 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); + + 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); + } + fallthrough; /* to default */ + + default: + error = n_tty_ioctl_helper(tty, 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 + * @wait: 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; + + /* + * 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"); + + 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, + .num = N_HDLC, + .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_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) +{ + tty_unregister_ldisc(&n_hdlc_ldisc); +} + +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); |