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e3b3d0f5 | 1 | // SPDX-License-Identifier: GPL-1.0+ |
1da177e4 LT |
2 | /* generic HDLC line discipline for Linux |
3 | * | |
4 | * Written by Paul Fulghum paulkf@microgate.com | |
5 | * for Microgate Corporation | |
6 | * | |
7 | * Microgate and SyncLink are registered trademarks of Microgate Corporation | |
8 | * | |
9 | * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>, | |
10 | * Al Longyear <longyear@netcom.com>, | |
11 | * Paul Mackerras <Paul.Mackerras@cs.anu.edu.au> | |
12 | * | |
13 | * Original release 01/11/99 | |
1da177e4 | 14 | * |
1da177e4 LT |
15 | * This module implements the tty line discipline N_HDLC for use with |
16 | * tty device drivers that support bit-synchronous HDLC communications. | |
17 | * | |
18 | * All HDLC data is frame oriented which means: | |
19 | * | |
20 | * 1. tty write calls represent one complete transmit frame of data | |
43741e9b | 21 | * The device driver should accept the complete frame or none of |
1da177e4 LT |
22 | * the frame (busy) in the write method. Each write call should have |
23 | * a byte count in the range of 2-65535 bytes (2 is min HDLC frame | |
24 | * with 1 addr byte and 1 ctrl byte). The max byte count of 65535 | |
25 | * should include any crc bytes required. For example, when using | |
26 | * CCITT CRC32, 4 crc bytes are required, so the maximum size frame | |
27 | * the application may transmit is limited to 65531 bytes. For CCITT | |
28 | * CRC16, the maximum application frame size would be 65533. | |
29 | * | |
30 | * | |
31 | * 2. receive callbacks from the device driver represents | |
32 | * one received frame. The device driver should bypass | |
33 | * the tty flip buffer and call the line discipline receive | |
34 | * callback directly to avoid fragmenting or concatenating | |
35 | * multiple frames into a single receive callback. | |
36 | * | |
37 | * The HDLC line discipline queues the receive frames in separate | |
38 | * buffers so complete receive frames can be returned by the | |
39 | * tty read calls. | |
40 | * | |
41 | * 3. tty read calls returns an entire frame of data or nothing. | |
43741e9b | 42 | * |
1da177e4 LT |
43 | * 4. all send and receive data is considered raw. No processing |
44 | * or translation is performed by the line discipline, regardless | |
45 | * of the tty flags | |
46 | * | |
47 | * 5. When line discipline is queried for the amount of receive | |
48 | * data available (FIOC), 0 is returned if no data available, | |
49 | * otherwise the count of the next available frame is returned. | |
50 | * (instead of the sum of all received frame counts). | |
51 | * | |
52 | * These conventions allow the standard tty programming interface | |
53 | * to be used for synchronous HDLC applications when used with | |
54 | * this line discipline (or another line discipline that is frame | |
55 | * oriented such as N_PPP). | |
56 | * | |
57 | * The SyncLink driver (synclink.c) implements both asynchronous | |
58 | * (using standard line discipline N_TTY) and synchronous HDLC | |
59 | * (using N_HDLC) communications, with the latter using the above | |
60 | * conventions. | |
61 | * | |
62 | * This implementation is very basic and does not maintain | |
63 | * any statistics. The main point is to enforce the raw data | |
64 | * and frame orientation of HDLC communications. | |
65 | * | |
66 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED | |
67 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
68 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE | |
69 | * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, | |
70 | * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES | |
71 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR | |
72 | * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
73 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, | |
74 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
75 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED | |
76 | * OF THE POSSIBILITY OF SUCH DAMAGE. | |
77 | */ | |
78 | ||
79 | #define HDLC_MAGIC 0x239e | |
1da177e4 | 80 | |
1da177e4 LT |
81 | #include <linux/module.h> |
82 | #include <linux/init.h> | |
83 | #include <linux/kernel.h> | |
84 | #include <linux/sched.h> | |
85 | #include <linux/types.h> | |
86 | #include <linux/fcntl.h> | |
87 | #include <linux/interrupt.h> | |
88 | #include <linux/ptrace.h> | |
89 | ||
1da177e4 LT |
90 | #include <linux/poll.h> |
91 | #include <linux/in.h> | |
92 | #include <linux/ioctl.h> | |
93 | #include <linux/slab.h> | |
94 | #include <linux/tty.h> | |
95 | #include <linux/errno.h> | |
96 | #include <linux/string.h> /* used in new tty drivers */ | |
97 | #include <linux/signal.h> /* used in new tty drivers */ | |
98 | #include <linux/if.h> | |
99 | #include <linux/bitops.h> | |
100 | ||
1da177e4 | 101 | #include <asm/termios.h> |
7c0f6ba6 | 102 | #include <linux/uaccess.h> |
5ffa6e34 | 103 | #include "tty.h" |
1da177e4 LT |
104 | |
105 | /* | |
106 | * Buffers for individual HDLC frames | |
107 | */ | |
43741e9b | 108 | #define MAX_HDLC_FRAME_SIZE 65535 |
1da177e4 LT |
109 | #define DEFAULT_RX_BUF_COUNT 10 |
110 | #define MAX_RX_BUF_COUNT 60 | |
be10eb75 | 111 | #define DEFAULT_TX_BUF_COUNT 3 |
1da177e4 LT |
112 | |
113 | struct n_hdlc_buf { | |
82f2341c | 114 | struct list_head list_item; |
1da177e4 | 115 | int count; |
85f4c951 | 116 | char buf[]; |
1da177e4 LT |
117 | }; |
118 | ||
1da177e4 | 119 | struct n_hdlc_buf_list { |
82f2341c | 120 | struct list_head list; |
1da177e4 LT |
121 | int count; |
122 | spinlock_t spinlock; | |
123 | }; | |
124 | ||
125 | /** | |
126 | * struct n_hdlc - per device instance data structure | |
724ac070 JS |
127 | * @magic: magic value for structure |
128 | * @tbusy: reentrancy flag for tx wakeup code | |
129 | * @woke_up: tx wakeup needs to be run again as it was called while @tbusy | |
130 | * @tx_buf_list: list of pending transmit frame buffers | |
131 | * @rx_buf_list: list of received frame buffers | |
132 | * @tx_free_buf_list: list unused transmit frame buffers | |
133 | * @rx_free_buf_list: list unused received frame buffers | |
1da177e4 LT |
134 | */ |
135 | struct n_hdlc { | |
136 | int magic; | |
0f238298 JS |
137 | bool tbusy; |
138 | bool woke_up; | |
1da177e4 LT |
139 | struct n_hdlc_buf_list tx_buf_list; |
140 | struct n_hdlc_buf_list rx_buf_list; | |
141 | struct n_hdlc_buf_list tx_free_buf_list; | |
142 | struct n_hdlc_buf_list rx_free_buf_list; | |
1ee33b1c TH |
143 | struct work_struct write_work; |
144 | struct tty_struct *tty_for_write_work; | |
1da177e4 LT |
145 | }; |
146 | ||
147 | /* | |
148 | * HDLC buffer list manipulation functions | |
149 | */ | |
82f2341c AP |
150 | static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, |
151 | struct n_hdlc_buf *buf); | |
1da177e4 LT |
152 | static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, |
153 | struct n_hdlc_buf *buf); | |
154 | static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list); | |
155 | ||
156 | /* Local functions */ | |
157 | ||
2bfb2b75 | 158 | static struct n_hdlc *n_hdlc_alloc(void); |
1ee33b1c | 159 | static void n_hdlc_tty_write_work(struct work_struct *work); |
1da177e4 | 160 | |
1da177e4 LT |
161 | /* max frame size for memory allocations */ |
162 | static int maxframe = 4096; | |
163 | ||
be10eb75 PF |
164 | static void flush_rx_queue(struct tty_struct *tty) |
165 | { | |
75011682 | 166 | struct n_hdlc *n_hdlc = tty->disc_data; |
be10eb75 PF |
167 | struct n_hdlc_buf *buf; |
168 | ||
169 | while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list))) | |
170 | n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf); | |
171 | } | |
172 | ||
173 | static void flush_tx_queue(struct tty_struct *tty) | |
174 | { | |
75011682 | 175 | struct n_hdlc *n_hdlc = tty->disc_data; |
be10eb75 | 176 | struct n_hdlc_buf *buf; |
be10eb75 PF |
177 | |
178 | while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list))) | |
179 | n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf); | |
be10eb75 PF |
180 | } |
181 | ||
30fafd92 JS |
182 | static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list) |
183 | { | |
184 | struct n_hdlc_buf *buf; | |
185 | ||
186 | do { | |
187 | buf = n_hdlc_buf_get(list); | |
188 | kfree(buf); | |
189 | } while (buf); | |
190 | } | |
191 | ||
1da177e4 LT |
192 | /** |
193 | * n_hdlc_tty_close - line discipline close | |
724ac070 | 194 | * @tty: pointer to tty info structure |
1da177e4 LT |
195 | * |
196 | * Called when the line discipline is changed to something | |
197 | * else, the tty is closed, or the tty detects a hangup. | |
198 | */ | |
199 | static void n_hdlc_tty_close(struct tty_struct *tty) | |
200 | { | |
75011682 | 201 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 | 202 | |
5f289514 | 203 | if (n_hdlc->magic != HDLC_MAGIC) { |
d86b05cb | 204 | pr_warn("n_hdlc: trying to close unopened tty!\n"); |
5f289514 JS |
205 | return; |
206 | } | |
1da177e4 | 207 | #if defined(TTY_NO_WRITE_SPLIT) |
8d79bb5c | 208 | clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags); |
1da177e4 | 209 | #endif |
5f289514 | 210 | tty->disc_data = NULL; |
43e784ec JS |
211 | |
212 | /* Ensure that the n_hdlcd process is not hanging on select()/poll() */ | |
213 | wake_up_interruptible(&tty->read_wait); | |
214 | wake_up_interruptible(&tty->write_wait); | |
215 | ||
1ee33b1c TH |
216 | cancel_work_sync(&n_hdlc->write_work); |
217 | ||
43e784ec JS |
218 | n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list); |
219 | n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list); | |
220 | n_hdlc_free_buf_list(&n_hdlc->rx_buf_list); | |
221 | n_hdlc_free_buf_list(&n_hdlc->tx_buf_list); | |
222 | kfree(n_hdlc); | |
1da177e4 LT |
223 | } /* end of n_hdlc_tty_close() */ |
224 | ||
225 | /** | |
226 | * n_hdlc_tty_open - called when line discipline changed to n_hdlc | |
724ac070 | 227 | * @tty: pointer to tty info structure |
1da177e4 LT |
228 | * |
229 | * Returns 0 if success, otherwise error code | |
230 | */ | |
2bfb2b75 | 231 | static int n_hdlc_tty_open(struct tty_struct *tty) |
1da177e4 | 232 | { |
75011682 | 233 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 | 234 | |
b18d1c2e | 235 | pr_debug("%s() called (device=%s)\n", __func__, tty->name); |
f3c2e277 | 236 | |
1da177e4 LT |
237 | /* There should not be an existing table for this slot. */ |
238 | if (n_hdlc) { | |
d86b05cb | 239 | pr_err("%s: tty already associated!\n", __func__); |
1da177e4 LT |
240 | return -EEXIST; |
241 | } | |
43741e9b | 242 | |
1da177e4 LT |
243 | n_hdlc = n_hdlc_alloc(); |
244 | if (!n_hdlc) { | |
d86b05cb | 245 | pr_err("%s: n_hdlc_alloc failed\n", __func__); |
1da177e4 LT |
246 | return -ENFILE; |
247 | } | |
43741e9b | 248 | |
1ee33b1c TH |
249 | INIT_WORK(&n_hdlc->write_work, n_hdlc_tty_write_work); |
250 | n_hdlc->tty_for_write_work = tty; | |
1da177e4 | 251 | tty->disc_data = n_hdlc; |
33f0f88f | 252 | tty->receive_room = 65536; |
43741e9b | 253 | |
1da177e4 | 254 | /* change tty_io write() to not split large writes into 8K chunks */ |
8d79bb5c | 255 | set_bit(TTY_NO_WRITE_SPLIT, &tty->flags); |
43741e9b | 256 | |
be10eb75 | 257 | /* flush receive data from driver */ |
f34d7a5b | 258 | tty_driver_flush_buffer(tty); |
66c3bdf1 | 259 | |
1da177e4 | 260 | return 0; |
43741e9b | 261 | |
1da177e4 LT |
262 | } /* end of n_tty_hdlc_open() */ |
263 | ||
264 | /** | |
265 | * n_hdlc_send_frames - send frames on pending send buffer list | |
724ac070 JS |
266 | * @n_hdlc: pointer to ldisc instance data |
267 | * @tty: pointer to tty instance data | |
1da177e4 LT |
268 | * |
269 | * Send frames on pending send buffer list until the driver does not accept a | |
270 | * frame (busy) this function is called after adding a frame to the send buffer | |
271 | * list and by the tty wakeup callback. | |
272 | */ | |
273 | static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) | |
274 | { | |
275 | register int actual; | |
276 | unsigned long flags; | |
277 | struct n_hdlc_buf *tbuf; | |
278 | ||
43741e9b JS |
279 | check_again: |
280 | ||
281 | spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); | |
1da177e4 | 282 | if (n_hdlc->tbusy) { |
0f238298 JS |
283 | n_hdlc->woke_up = true; |
284 | spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); | |
1da177e4 LT |
285 | return; |
286 | } | |
0f238298 JS |
287 | n_hdlc->tbusy = true; |
288 | n_hdlc->woke_up = false; | |
1da177e4 LT |
289 | spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); |
290 | ||
82f2341c | 291 | tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); |
1da177e4 | 292 | while (tbuf) { |
b18d1c2e | 293 | pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count); |
f3c2e277 | 294 | |
1da177e4 | 295 | /* Send the next block of data to device */ |
7962fce9 | 296 | set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); |
f34d7a5b | 297 | actual = tty->ops->write(tty, tbuf->buf, tbuf->count); |
b0fed314 JS |
298 | |
299 | /* rollback was possible and has been done */ | |
300 | if (actual == -ERESTARTSYS) { | |
82f2341c | 301 | n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); |
b0fed314 JS |
302 | break; |
303 | } | |
1da177e4 LT |
304 | /* if transmit error, throw frame away by */ |
305 | /* pretending it was accepted by driver */ | |
306 | if (actual < 0) | |
307 | actual = tbuf->count; | |
43741e9b | 308 | |
1da177e4 | 309 | if (actual == tbuf->count) { |
b18d1c2e | 310 | pr_debug("frame %p completed\n", tbuf); |
f3c2e277 | 311 | |
1da177e4 LT |
312 | /* free current transmit buffer */ |
313 | n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf); | |
82f2341c | 314 | |
1da177e4 LT |
315 | /* wait up sleeping writers */ |
316 | wake_up_interruptible(&tty->write_wait); | |
43741e9b | 317 | |
1da177e4 LT |
318 | /* get next pending transmit buffer */ |
319 | tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); | |
320 | } else { | |
b18d1c2e | 321 | pr_debug("frame %p pending\n", tbuf); |
82f2341c AP |
322 | |
323 | /* | |
324 | * the buffer was not accepted by driver, | |
325 | * return it back into tx queue | |
326 | */ | |
327 | n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); | |
1da177e4 LT |
328 | break; |
329 | } | |
330 | } | |
43741e9b | 331 | |
1da177e4 | 332 | if (!tbuf) |
7962fce9 | 333 | clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); |
43741e9b | 334 | |
1da177e4 LT |
335 | /* Clear the re-entry flag */ |
336 | spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); | |
0f238298 | 337 | n_hdlc->tbusy = false; |
43741e9b JS |
338 | spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); |
339 | ||
340 | if (n_hdlc->woke_up) | |
341 | goto check_again; | |
1da177e4 LT |
342 | } /* end of n_hdlc_send_frames() */ |
343 | ||
1ee33b1c TH |
344 | /** |
345 | * n_hdlc_tty_write_work - Asynchronous callback for transmit wakeup | |
346 | * @work: pointer to work_struct | |
347 | * | |
348 | * Called when low level device driver can accept more send data. | |
349 | */ | |
350 | static void n_hdlc_tty_write_work(struct work_struct *work) | |
351 | { | |
352 | struct n_hdlc *n_hdlc = container_of(work, struct n_hdlc, write_work); | |
353 | struct tty_struct *tty = n_hdlc->tty_for_write_work; | |
354 | ||
355 | n_hdlc_send_frames(n_hdlc, tty); | |
356 | } /* end of n_hdlc_tty_write_work() */ | |
357 | ||
1da177e4 LT |
358 | /** |
359 | * n_hdlc_tty_wakeup - Callback for transmit wakeup | |
724ac070 | 360 | * @tty: pointer to associated tty instance data |
1da177e4 LT |
361 | * |
362 | * Called when low level device driver can accept more send data. | |
363 | */ | |
364 | static void n_hdlc_tty_wakeup(struct tty_struct *tty) | |
365 | { | |
75011682 | 366 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 | 367 | |
1ee33b1c | 368 | schedule_work(&n_hdlc->write_work); |
1da177e4 LT |
369 | } /* end of n_hdlc_tty_wakeup() */ |
370 | ||
1da177e4 LT |
371 | /** |
372 | * n_hdlc_tty_receive - Called by tty driver when receive data is available | |
724ac070 JS |
373 | * @tty: pointer to tty instance data |
374 | * @data: pointer to received data | |
375 | * @flags: pointer to flags for data | |
376 | * @count: count of received data in bytes | |
1da177e4 LT |
377 | * |
378 | * Called by tty low level driver when receive data is available. Data is | |
379 | * interpreted as one HDLC frame. | |
380 | */ | |
55db4c64 | 381 | static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data, |
0f3dcf3b | 382 | const char *flags, int count) |
1da177e4 | 383 | { |
75011682 | 384 | register struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 LT |
385 | register struct n_hdlc_buf *buf; |
386 | ||
b18d1c2e | 387 | pr_debug("%s() called count=%d\n", __func__, count); |
f3c2e277 | 388 | |
1da177e4 LT |
389 | /* verify line is using HDLC discipline */ |
390 | if (n_hdlc->magic != HDLC_MAGIC) { | |
b18d1c2e | 391 | pr_err("line not using HDLC discipline\n"); |
55db4c64 | 392 | return; |
1da177e4 | 393 | } |
43741e9b | 394 | |
1283c721 | 395 | if (count > maxframe) { |
b18d1c2e | 396 | pr_debug("rx count>maxframesize, data discarded\n"); |
55db4c64 | 397 | return; |
1da177e4 LT |
398 | } |
399 | ||
43741e9b | 400 | /* get a free HDLC buffer */ |
1da177e4 LT |
401 | buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list); |
402 | if (!buf) { | |
80967ff2 JS |
403 | /* |
404 | * no buffers in free list, attempt to allocate another rx | |
405 | * buffer unless the maximum count has been reached | |
406 | */ | |
1da177e4 | 407 | if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT) |
85f4c951 GS |
408 | buf = kmalloc(struct_size(buf, buf, maxframe), |
409 | GFP_ATOMIC); | |
1da177e4 | 410 | } |
43741e9b | 411 | |
1da177e4 | 412 | if (!buf) { |
b18d1c2e | 413 | pr_debug("no more rx buffers, data discarded\n"); |
55db4c64 | 414 | return; |
1da177e4 | 415 | } |
43741e9b | 416 | |
1da177e4 | 417 | /* copy received data to HDLC buffer */ |
8d79bb5c | 418 | memcpy(buf->buf, data, count); |
1283c721 | 419 | buf->count = count; |
1da177e4 LT |
420 | |
421 | /* add HDLC buffer to list of received frames */ | |
422 | n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf); | |
43741e9b | 423 | |
1da177e4 | 424 | /* wake up any blocked reads and perform async signalling */ |
2bfb2b75 | 425 | wake_up_interruptible(&tty->read_wait); |
df6de639 JS |
426 | if (tty->fasync != NULL) |
427 | kill_fasync(&tty->fasync, SIGIO, POLL_IN); | |
1da177e4 LT |
428 | |
429 | } /* end of n_hdlc_tty_receive() */ | |
430 | ||
431 | /** | |
4a4efbde | 432 | * n_hdlc_tty_read - Called to retrieve one frame of data (if available) |
724ac070 JS |
433 | * @tty: pointer to tty instance data |
434 | * @file: pointer to open file object | |
ef80f77b | 435 | * @kbuf: pointer to returned data buffer |
724ac070 | 436 | * @nr: size of returned data buffer |
ef80f77b LJ |
437 | * @cookie: stored rbuf from previous run |
438 | * @offset: offset into the data buffer | |
43741e9b | 439 | * |
1da177e4 LT |
440 | * Returns the number of bytes returned or error code. |
441 | */ | |
442 | static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, | |
3b830a9c LT |
443 | __u8 *kbuf, size_t nr, |
444 | void **cookie, unsigned long offset) | |
1da177e4 | 445 | { |
75011682 | 446 | struct n_hdlc *n_hdlc = tty->disc_data; |
1035b63d | 447 | int ret = 0; |
1da177e4 | 448 | struct n_hdlc_buf *rbuf; |
1035b63d | 449 | DECLARE_WAITQUEUE(wait, current); |
1da177e4 | 450 | |
3b830a9c LT |
451 | /* Is this a repeated call for an rbuf we already found earlier? */ |
452 | rbuf = *cookie; | |
453 | if (rbuf) | |
454 | goto have_rbuf; | |
455 | ||
1035b63d | 456 | add_wait_queue(&tty->read_wait, &wait); |
04f378b1 | 457 | |
1da177e4 | 458 | for (;;) { |
0f40fbbc | 459 | if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { |
1035b63d PF |
460 | ret = -EIO; |
461 | break; | |
04f378b1 | 462 | } |
1035b63d PF |
463 | if (tty_hung_up_p(file)) |
464 | break; | |
1da177e4 | 465 | |
1035b63d | 466 | set_current_state(TASK_INTERRUPTIBLE); |
1da177e4 LT |
467 | |
468 | rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list); | |
3b830a9c | 469 | if (rbuf) |
1da177e4 | 470 | break; |
43741e9b | 471 | |
1da177e4 | 472 | /* no data */ |
c96cf923 | 473 | if (tty_io_nonblock(tty, file)) { |
1035b63d PF |
474 | ret = -EAGAIN; |
475 | break; | |
04f378b1 | 476 | } |
1035b63d PF |
477 | |
478 | schedule(); | |
479 | ||
04f378b1 | 480 | if (signal_pending(current)) { |
1035b63d PF |
481 | ret = -EINTR; |
482 | break; | |
04f378b1 | 483 | } |
1da177e4 | 484 | } |
1035b63d PF |
485 | |
486 | remove_wait_queue(&tty->read_wait, &wait); | |
487 | __set_current_state(TASK_RUNNING); | |
488 | ||
3b830a9c LT |
489 | if (!rbuf) |
490 | return ret; | |
491 | *cookie = rbuf; | |
492 | ||
493 | have_rbuf: | |
494 | /* Have we used it up entirely? */ | |
495 | if (offset >= rbuf->count) | |
496 | goto done_with_rbuf; | |
497 | ||
498 | /* More data to go, but can't copy any more? EOVERFLOW */ | |
499 | ret = -EOVERFLOW; | |
500 | if (!nr) | |
501 | goto done_with_rbuf; | |
502 | ||
503 | /* Copy as much data as possible */ | |
504 | ret = rbuf->count - offset; | |
505 | if (ret > nr) | |
506 | ret = nr; | |
507 | memcpy(kbuf, rbuf->buf+offset, ret); | |
508 | offset += ret; | |
509 | ||
510 | /* If we still have data left, we leave the rbuf in the cookie */ | |
511 | if (offset < rbuf->count) | |
512 | return ret; | |
513 | ||
514 | done_with_rbuf: | |
515 | *cookie = NULL; | |
516 | ||
517 | if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT) | |
518 | kfree(rbuf); | |
519 | else | |
520 | n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf); | |
521 | ||
1da177e4 | 522 | return ret; |
43741e9b | 523 | |
1da177e4 LT |
524 | } /* end of n_hdlc_tty_read() */ |
525 | ||
526 | /** | |
527 | * n_hdlc_tty_write - write a single frame of data to device | |
724ac070 JS |
528 | * @tty: pointer to associated tty device instance data |
529 | * @file: pointer to file object data | |
530 | * @data: pointer to transmit data (one frame) | |
531 | * @count: size of transmit frame in bytes | |
43741e9b | 532 | * |
1da177e4 LT |
533 | * Returns the number of bytes written (or error code). |
534 | */ | |
535 | static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, | |
536 | const unsigned char *data, size_t count) | |
537 | { | |
75011682 | 538 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 LT |
539 | int error = 0; |
540 | DECLARE_WAITQUEUE(wait, current); | |
541 | struct n_hdlc_buf *tbuf; | |
542 | ||
b18d1c2e | 543 | pr_debug("%s() called count=%zd\n", __func__, count); |
f3c2e277 | 544 | |
1da177e4 LT |
545 | if (n_hdlc->magic != HDLC_MAGIC) |
546 | return -EIO; | |
547 | ||
548 | /* verify frame size */ | |
1283c721 | 549 | if (count > maxframe) { |
f3c2e277 JS |
550 | pr_debug("%s: truncating user packet from %zu to %d\n", |
551 | __func__, count, maxframe); | |
1da177e4 LT |
552 | count = maxframe; |
553 | } | |
43741e9b | 554 | |
1da177e4 | 555 | add_wait_queue(&tty->write_wait, &wait); |
1035b63d PF |
556 | |
557 | for (;;) { | |
558 | set_current_state(TASK_INTERRUPTIBLE); | |
43741e9b | 559 | |
1035b63d PF |
560 | tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list); |
561 | if (tbuf) | |
562 | break; | |
563 | ||
c96cf923 | 564 | if (tty_io_nonblock(tty, file)) { |
c72f527c PF |
565 | error = -EAGAIN; |
566 | break; | |
567 | } | |
1da177e4 | 568 | schedule(); |
844cc5f9 | 569 | |
1da177e4 LT |
570 | if (signal_pending(current)) { |
571 | error = -EINTR; | |
572 | break; | |
573 | } | |
574 | } | |
575 | ||
1035b63d | 576 | __set_current_state(TASK_RUNNING); |
1da177e4 LT |
577 | remove_wait_queue(&tty->write_wait, &wait); |
578 | ||
43741e9b | 579 | if (!error) { |
1da177e4 LT |
580 | /* Retrieve the user's buffer */ |
581 | memcpy(tbuf->buf, data, count); | |
582 | ||
583 | /* Send the data */ | |
584 | tbuf->count = error = count; | |
8d79bb5c JS |
585 | n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf); |
586 | n_hdlc_send_frames(n_hdlc, tty); | |
1da177e4 | 587 | } |
1035b63d | 588 | |
1da177e4 | 589 | return error; |
43741e9b | 590 | |
1da177e4 LT |
591 | } /* end of n_hdlc_tty_write() */ |
592 | ||
593 | /** | |
594 | * n_hdlc_tty_ioctl - process IOCTL system call for the tty device. | |
724ac070 | 595 | * @tty: pointer to tty instance data |
724ac070 JS |
596 | * @cmd: IOCTL command code |
597 | * @arg: argument for IOCTL call (cmd dependent) | |
1da177e4 LT |
598 | * |
599 | * Returns command dependent result. | |
600 | */ | |
d78328bc JS |
601 | static int n_hdlc_tty_ioctl(struct tty_struct *tty, unsigned int cmd, |
602 | unsigned long arg) | |
1da177e4 | 603 | { |
75011682 | 604 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 LT |
605 | int error = 0; |
606 | int count; | |
607 | unsigned long flags; | |
82f2341c AP |
608 | struct n_hdlc_buf *buf = NULL; |
609 | ||
b18d1c2e | 610 | pr_debug("%s() called %d\n", __func__, cmd); |
f3c2e277 | 611 | |
1da177e4 | 612 | /* Verify the status of the device */ |
844cc5f9 | 613 | if (n_hdlc->magic != HDLC_MAGIC) |
1da177e4 LT |
614 | return -EBADF; |
615 | ||
616 | switch (cmd) { | |
617 | case FIONREAD: | |
618 | /* report count of read data available */ | |
619 | /* in next available frame (if any) */ | |
8d79bb5c | 620 | spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags); |
82f2341c AP |
621 | buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list, |
622 | struct n_hdlc_buf, list_item); | |
623 | if (buf) | |
624 | count = buf->count; | |
1da177e4 LT |
625 | else |
626 | count = 0; | |
8d79bb5c | 627 | spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags); |
1da177e4 LT |
628 | error = put_user(count, (int __user *)arg); |
629 | break; | |
630 | ||
631 | case TIOCOUTQ: | |
632 | /* get the pending tx byte count in the driver */ | |
f34d7a5b | 633 | count = tty_chars_in_buffer(tty); |
1da177e4 | 634 | /* add size of next output frame in queue */ |
8d79bb5c | 635 | spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); |
82f2341c AP |
636 | buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list, |
637 | struct n_hdlc_buf, list_item); | |
638 | if (buf) | |
639 | count += buf->count; | |
8d79bb5c | 640 | spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); |
1da177e4 LT |
641 | error = put_user(count, (int __user *)arg); |
642 | break; | |
643 | ||
be10eb75 PF |
644 | case TCFLSH: |
645 | switch (arg) { | |
646 | case TCIOFLUSH: | |
647 | case TCOFLUSH: | |
648 | flush_tx_queue(tty); | |
649 | } | |
df561f66 | 650 | fallthrough; /* to default */ |
be10eb75 | 651 | |
1da177e4 | 652 | default: |
7c783601 | 653 | error = n_tty_ioctl_helper(tty, cmd, arg); |
1da177e4 LT |
654 | break; |
655 | } | |
656 | return error; | |
43741e9b | 657 | |
1da177e4 LT |
658 | } /* end of n_hdlc_tty_ioctl() */ |
659 | ||
660 | /** | |
661 | * n_hdlc_tty_poll - TTY callback for poll system call | |
724ac070 JS |
662 | * @tty: pointer to tty instance data |
663 | * @filp: pointer to open file object for device | |
664 | * @wait: wait queue for operations | |
43741e9b | 665 | * |
1da177e4 LT |
666 | * Determine which operations (read/write) will not block and return info |
667 | * to caller. | |
668 | * Returns a bit mask containing info on which ops will not block. | |
669 | */ | |
afc9a42b | 670 | static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, |
1da177e4 LT |
671 | poll_table *wait) |
672 | { | |
75011682 | 673 | struct n_hdlc *n_hdlc = tty->disc_data; |
afc9a42b | 674 | __poll_t mask = 0; |
1da177e4 | 675 | |
844cc5f9 | 676 | if (n_hdlc->magic != HDLC_MAGIC) |
5f289514 JS |
677 | return 0; |
678 | ||
679 | /* | |
680 | * queue the current process into any wait queue that may awaken in the | |
681 | * future (read and write) | |
682 | */ | |
683 | poll_wait(filp, &tty->read_wait, wait); | |
684 | poll_wait(filp, &tty->write_wait, wait); | |
685 | ||
686 | /* set bits for operations that won't block */ | |
687 | if (!list_empty(&n_hdlc->rx_buf_list.list)) | |
688 | mask |= EPOLLIN | EPOLLRDNORM; /* readable */ | |
689 | if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) | |
690 | mask |= EPOLLHUP; | |
691 | if (tty_hung_up_p(filp)) | |
692 | mask |= EPOLLHUP; | |
693 | if (!tty_is_writelocked(tty) && | |
694 | !list_empty(&n_hdlc->tx_free_buf_list.list)) | |
695 | mask |= EPOLLOUT | EPOLLWRNORM; /* writable */ | |
696 | ||
1da177e4 LT |
697 | return mask; |
698 | } /* end of n_hdlc_tty_poll() */ | |
699 | ||
740708ab JS |
700 | static void n_hdlc_alloc_buf(struct n_hdlc_buf_list *list, unsigned int count, |
701 | const char *name) | |
702 | { | |
703 | struct n_hdlc_buf *buf; | |
704 | unsigned int i; | |
705 | ||
706 | for (i = 0; i < count; i++) { | |
707 | buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL); | |
708 | if (!buf) { | |
b18d1c2e JS |
709 | pr_debug("%s(), kmalloc() failed for %s buffer %u\n", |
710 | __func__, name, i); | |
740708ab JS |
711 | return; |
712 | } | |
713 | n_hdlc_buf_put(list, buf); | |
714 | } | |
715 | } | |
716 | ||
1da177e4 LT |
717 | /** |
718 | * n_hdlc_alloc - allocate an n_hdlc instance data structure | |
719 | * | |
720 | * Returns a pointer to newly created structure if success, otherwise %NULL | |
721 | */ | |
722 | static struct n_hdlc *n_hdlc_alloc(void) | |
723 | { | |
8e25f8ce | 724 | struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL); |
1da177e4 LT |
725 | |
726 | if (!n_hdlc) | |
727 | return NULL; | |
728 | ||
e9b736d8 JS |
729 | spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock); |
730 | spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock); | |
731 | spin_lock_init(&n_hdlc->rx_buf_list.spinlock); | |
732 | spin_lock_init(&n_hdlc->tx_buf_list.spinlock); | |
82f2341c AP |
733 | |
734 | INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list); | |
735 | INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list); | |
736 | INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list); | |
737 | INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list); | |
738 | ||
740708ab JS |
739 | n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx"); |
740 | n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx"); | |
741 | ||
1da177e4 LT |
742 | /* Initialize the control block */ |
743 | n_hdlc->magic = HDLC_MAGIC; | |
a1274b26 | 744 | |
1da177e4 | 745 | return n_hdlc; |
43741e9b | 746 | |
1da177e4 LT |
747 | } /* end of n_hdlc_alloc() */ |
748 | ||
82f2341c AP |
749 | /** |
750 | * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list | |
724ac070 JS |
751 | * @buf_list: pointer to the buffer list |
752 | * @buf: pointer to the buffer | |
82f2341c AP |
753 | */ |
754 | static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, | |
755 | struct n_hdlc_buf *buf) | |
756 | { | |
757 | unsigned long flags; | |
758 | ||
759 | spin_lock_irqsave(&buf_list->spinlock, flags); | |
760 | ||
761 | list_add(&buf->list_item, &buf_list->list); | |
762 | buf_list->count++; | |
763 | ||
764 | spin_unlock_irqrestore(&buf_list->spinlock, flags); | |
765 | } | |
766 | ||
1da177e4 LT |
767 | /** |
768 | * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list | |
724ac070 JS |
769 | * @buf_list: pointer to buffer list |
770 | * @buf: pointer to buffer | |
1da177e4 | 771 | */ |
82f2341c | 772 | static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list, |
1da177e4 LT |
773 | struct n_hdlc_buf *buf) |
774 | { | |
775 | unsigned long flags; | |
82f2341c AP |
776 | |
777 | spin_lock_irqsave(&buf_list->spinlock, flags); | |
778 | ||
779 | list_add_tail(&buf->list_item, &buf_list->list); | |
780 | buf_list->count++; | |
781 | ||
782 | spin_unlock_irqrestore(&buf_list->spinlock, flags); | |
1da177e4 LT |
783 | } /* end of n_hdlc_buf_put() */ |
784 | ||
785 | /** | |
786 | * n_hdlc_buf_get - remove and return an HDLC buffer from list | |
724ac070 | 787 | * @buf_list: pointer to HDLC buffer list |
43741e9b | 788 | * |
1da177e4 LT |
789 | * Remove and return an HDLC buffer from the head of the specified HDLC buffer |
790 | * list. | |
791 | * Returns a pointer to HDLC buffer if available, otherwise %NULL. | |
792 | */ | |
82f2341c | 793 | static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list) |
1da177e4 LT |
794 | { |
795 | unsigned long flags; | |
796 | struct n_hdlc_buf *buf; | |
82f2341c AP |
797 | |
798 | spin_lock_irqsave(&buf_list->spinlock, flags); | |
799 | ||
800 | buf = list_first_entry_or_null(&buf_list->list, | |
801 | struct n_hdlc_buf, list_item); | |
1da177e4 | 802 | if (buf) { |
82f2341c AP |
803 | list_del(&buf->list_item); |
804 | buf_list->count--; | |
1da177e4 | 805 | } |
82f2341c AP |
806 | |
807 | spin_unlock_irqrestore(&buf_list->spinlock, flags); | |
1da177e4 | 808 | return buf; |
1da177e4 LT |
809 | } /* end of n_hdlc_buf_get() */ |
810 | ||
edee649f JS |
811 | static struct tty_ldisc_ops n_hdlc_ldisc = { |
812 | .owner = THIS_MODULE, | |
fbadf70a | 813 | .num = N_HDLC, |
edee649f JS |
814 | .name = "hdlc", |
815 | .open = n_hdlc_tty_open, | |
816 | .close = n_hdlc_tty_close, | |
817 | .read = n_hdlc_tty_read, | |
818 | .write = n_hdlc_tty_write, | |
819 | .ioctl = n_hdlc_tty_ioctl, | |
820 | .poll = n_hdlc_tty_poll, | |
821 | .receive_buf = n_hdlc_tty_receive, | |
822 | .write_wakeup = n_hdlc_tty_wakeup, | |
823 | .flush_buffer = flush_rx_queue, | |
824 | }; | |
825 | ||
1da177e4 LT |
826 | static int __init n_hdlc_init(void) |
827 | { | |
828 | int status; | |
829 | ||
830 | /* range check maxframe arg */ | |
c549725f | 831 | maxframe = clamp(maxframe, 4096, MAX_HDLC_FRAME_SIZE); |
1da177e4 | 832 | |
fbadf70a | 833 | status = tty_register_ldisc(&n_hdlc_ldisc); |
1da177e4 | 834 | if (!status) |
cda3756c JS |
835 | pr_info("N_HDLC line discipline registered with maxframe=%d\n", |
836 | maxframe); | |
1da177e4 | 837 | else |
cda3756c JS |
838 | pr_err("N_HDLC: error registering line discipline: %d\n", |
839 | status); | |
1da177e4 | 840 | |
1da177e4 | 841 | return status; |
43741e9b | 842 | |
1da177e4 LT |
843 | } /* end of init_module() */ |
844 | ||
1da177e4 LT |
845 | static void __exit n_hdlc_exit(void) |
846 | { | |
357a6a87 | 847 | tty_unregister_ldisc(&n_hdlc_ldisc); |
1da177e4 LT |
848 | } |
849 | ||
850 | module_init(n_hdlc_init); | |
851 | module_exit(n_hdlc_exit); | |
852 | ||
853 | MODULE_LICENSE("GPL"); | |
854 | MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com"); | |
1da177e4 LT |
855 | module_param(maxframe, int, 0); |
856 | MODULE_ALIAS_LDISC(N_HDLC); |