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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> |
1da177e4 LT |
103 | |
104 | /* | |
105 | * Buffers for individual HDLC frames | |
106 | */ | |
43741e9b | 107 | #define MAX_HDLC_FRAME_SIZE 65535 |
1da177e4 LT |
108 | #define DEFAULT_RX_BUF_COUNT 10 |
109 | #define MAX_RX_BUF_COUNT 60 | |
be10eb75 | 110 | #define DEFAULT_TX_BUF_COUNT 3 |
1da177e4 LT |
111 | |
112 | struct n_hdlc_buf { | |
82f2341c | 113 | struct list_head list_item; |
1da177e4 | 114 | int count; |
85f4c951 | 115 | char buf[]; |
1da177e4 LT |
116 | }; |
117 | ||
1da177e4 | 118 | struct n_hdlc_buf_list { |
82f2341c | 119 | struct list_head list; |
1da177e4 LT |
120 | int count; |
121 | spinlock_t spinlock; | |
122 | }; | |
123 | ||
124 | /** | |
125 | * struct n_hdlc - per device instance data structure | |
126 | * @magic - magic value for structure | |
1da177e4 | 127 | * @tbusy - reentrancy flag for tx wakeup code |
0f238298 | 128 | * @woke_up - tx wakeup needs to be run again as it was called while @tbusy |
1da177e4 LT |
129 | * @tx_buf_list - list of pending transmit frame buffers |
130 | * @rx_buf_list - list of received frame buffers | |
131 | * @tx_free_buf_list - list unused transmit frame buffers | |
132 | * @rx_free_buf_list - list unused received frame buffers | |
133 | */ | |
134 | struct n_hdlc { | |
135 | int magic; | |
0f238298 JS |
136 | bool tbusy; |
137 | bool woke_up; | |
1da177e4 LT |
138 | struct n_hdlc_buf_list tx_buf_list; |
139 | struct n_hdlc_buf_list rx_buf_list; | |
140 | struct n_hdlc_buf_list tx_free_buf_list; | |
141 | struct n_hdlc_buf_list rx_free_buf_list; | |
142 | }; | |
143 | ||
144 | /* | |
145 | * HDLC buffer list manipulation functions | |
146 | */ | |
82f2341c AP |
147 | static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, |
148 | struct n_hdlc_buf *buf); | |
1da177e4 LT |
149 | static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, |
150 | struct n_hdlc_buf *buf); | |
151 | static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list); | |
152 | ||
153 | /* Local functions */ | |
154 | ||
2bfb2b75 | 155 | static struct n_hdlc *n_hdlc_alloc(void); |
1da177e4 | 156 | |
1da177e4 LT |
157 | /* max frame size for memory allocations */ |
158 | static int maxframe = 4096; | |
159 | ||
be10eb75 PF |
160 | static void flush_rx_queue(struct tty_struct *tty) |
161 | { | |
75011682 | 162 | struct n_hdlc *n_hdlc = tty->disc_data; |
be10eb75 PF |
163 | struct n_hdlc_buf *buf; |
164 | ||
165 | while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list))) | |
166 | n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf); | |
167 | } | |
168 | ||
169 | static void flush_tx_queue(struct tty_struct *tty) | |
170 | { | |
75011682 | 171 | struct n_hdlc *n_hdlc = tty->disc_data; |
be10eb75 | 172 | struct n_hdlc_buf *buf; |
be10eb75 PF |
173 | |
174 | while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list))) | |
175 | n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf); | |
be10eb75 PF |
176 | } |
177 | ||
30fafd92 JS |
178 | static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list) |
179 | { | |
180 | struct n_hdlc_buf *buf; | |
181 | ||
182 | do { | |
183 | buf = n_hdlc_buf_get(list); | |
184 | kfree(buf); | |
185 | } while (buf); | |
186 | } | |
187 | ||
1da177e4 LT |
188 | /** |
189 | * n_hdlc_tty_close - line discipline close | |
190 | * @tty - pointer to tty info structure | |
191 | * | |
192 | * Called when the line discipline is changed to something | |
193 | * else, the tty is closed, or the tty detects a hangup. | |
194 | */ | |
195 | static void n_hdlc_tty_close(struct tty_struct *tty) | |
196 | { | |
75011682 | 197 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 | 198 | |
5f289514 | 199 | if (n_hdlc->magic != HDLC_MAGIC) { |
d86b05cb | 200 | pr_warn("n_hdlc: trying to close unopened tty!\n"); |
5f289514 JS |
201 | return; |
202 | } | |
1da177e4 | 203 | #if defined(TTY_NO_WRITE_SPLIT) |
8d79bb5c | 204 | clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags); |
1da177e4 | 205 | #endif |
5f289514 | 206 | tty->disc_data = NULL; |
43e784ec JS |
207 | |
208 | /* Ensure that the n_hdlcd process is not hanging on select()/poll() */ | |
209 | wake_up_interruptible(&tty->read_wait); | |
210 | wake_up_interruptible(&tty->write_wait); | |
211 | ||
212 | n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list); | |
213 | n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list); | |
214 | n_hdlc_free_buf_list(&n_hdlc->rx_buf_list); | |
215 | n_hdlc_free_buf_list(&n_hdlc->tx_buf_list); | |
216 | kfree(n_hdlc); | |
1da177e4 LT |
217 | } /* end of n_hdlc_tty_close() */ |
218 | ||
219 | /** | |
220 | * n_hdlc_tty_open - called when line discipline changed to n_hdlc | |
221 | * @tty - pointer to tty info structure | |
222 | * | |
223 | * Returns 0 if success, otherwise error code | |
224 | */ | |
2bfb2b75 | 225 | static int n_hdlc_tty_open(struct tty_struct *tty) |
1da177e4 | 226 | { |
75011682 | 227 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 | 228 | |
b18d1c2e | 229 | pr_debug("%s() called (device=%s)\n", __func__, tty->name); |
f3c2e277 | 230 | |
1da177e4 LT |
231 | /* There should not be an existing table for this slot. */ |
232 | if (n_hdlc) { | |
d86b05cb | 233 | pr_err("%s: tty already associated!\n", __func__); |
1da177e4 LT |
234 | return -EEXIST; |
235 | } | |
43741e9b | 236 | |
1da177e4 LT |
237 | n_hdlc = n_hdlc_alloc(); |
238 | if (!n_hdlc) { | |
d86b05cb | 239 | pr_err("%s: n_hdlc_alloc failed\n", __func__); |
1da177e4 LT |
240 | return -ENFILE; |
241 | } | |
43741e9b | 242 | |
1da177e4 | 243 | tty->disc_data = n_hdlc; |
33f0f88f | 244 | tty->receive_room = 65536; |
43741e9b | 245 | |
1da177e4 | 246 | /* change tty_io write() to not split large writes into 8K chunks */ |
8d79bb5c | 247 | set_bit(TTY_NO_WRITE_SPLIT, &tty->flags); |
43741e9b | 248 | |
be10eb75 | 249 | /* flush receive data from driver */ |
f34d7a5b | 250 | tty_driver_flush_buffer(tty); |
66c3bdf1 | 251 | |
1da177e4 | 252 | return 0; |
43741e9b | 253 | |
1da177e4 LT |
254 | } /* end of n_tty_hdlc_open() */ |
255 | ||
256 | /** | |
257 | * n_hdlc_send_frames - send frames on pending send buffer list | |
258 | * @n_hdlc - pointer to ldisc instance data | |
259 | * @tty - pointer to tty instance data | |
260 | * | |
261 | * Send frames on pending send buffer list until the driver does not accept a | |
262 | * frame (busy) this function is called after adding a frame to the send buffer | |
263 | * list and by the tty wakeup callback. | |
264 | */ | |
265 | static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) | |
266 | { | |
267 | register int actual; | |
268 | unsigned long flags; | |
269 | struct n_hdlc_buf *tbuf; | |
270 | ||
43741e9b JS |
271 | check_again: |
272 | ||
273 | spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); | |
1da177e4 | 274 | if (n_hdlc->tbusy) { |
0f238298 JS |
275 | n_hdlc->woke_up = true; |
276 | spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); | |
1da177e4 LT |
277 | return; |
278 | } | |
0f238298 JS |
279 | n_hdlc->tbusy = true; |
280 | n_hdlc->woke_up = false; | |
1da177e4 LT |
281 | spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); |
282 | ||
82f2341c | 283 | tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); |
1da177e4 | 284 | while (tbuf) { |
b18d1c2e | 285 | pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count); |
f3c2e277 | 286 | |
1da177e4 | 287 | /* Send the next block of data to device */ |
7962fce9 | 288 | set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); |
f34d7a5b | 289 | actual = tty->ops->write(tty, tbuf->buf, tbuf->count); |
b0fed314 JS |
290 | |
291 | /* rollback was possible and has been done */ | |
292 | if (actual == -ERESTARTSYS) { | |
82f2341c | 293 | n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); |
b0fed314 JS |
294 | break; |
295 | } | |
1da177e4 LT |
296 | /* if transmit error, throw frame away by */ |
297 | /* pretending it was accepted by driver */ | |
298 | if (actual < 0) | |
299 | actual = tbuf->count; | |
43741e9b | 300 | |
1da177e4 | 301 | if (actual == tbuf->count) { |
b18d1c2e | 302 | pr_debug("frame %p completed\n", tbuf); |
f3c2e277 | 303 | |
1da177e4 LT |
304 | /* free current transmit buffer */ |
305 | n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf); | |
82f2341c | 306 | |
1da177e4 LT |
307 | /* wait up sleeping writers */ |
308 | wake_up_interruptible(&tty->write_wait); | |
43741e9b | 309 | |
1da177e4 LT |
310 | /* get next pending transmit buffer */ |
311 | tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); | |
312 | } else { | |
b18d1c2e | 313 | pr_debug("frame %p pending\n", tbuf); |
82f2341c AP |
314 | |
315 | /* | |
316 | * the buffer was not accepted by driver, | |
317 | * return it back into tx queue | |
318 | */ | |
319 | n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); | |
1da177e4 LT |
320 | break; |
321 | } | |
322 | } | |
43741e9b | 323 | |
1da177e4 | 324 | if (!tbuf) |
7962fce9 | 325 | clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); |
43741e9b | 326 | |
1da177e4 LT |
327 | /* Clear the re-entry flag */ |
328 | spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); | |
0f238298 | 329 | n_hdlc->tbusy = false; |
43741e9b JS |
330 | spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); |
331 | ||
332 | if (n_hdlc->woke_up) | |
333 | goto check_again; | |
1da177e4 LT |
334 | } /* end of n_hdlc_send_frames() */ |
335 | ||
336 | /** | |
337 | * n_hdlc_tty_wakeup - Callback for transmit wakeup | |
338 | * @tty - pointer to associated tty instance data | |
339 | * | |
340 | * Called when low level device driver can accept more send data. | |
341 | */ | |
342 | static void n_hdlc_tty_wakeup(struct tty_struct *tty) | |
343 | { | |
75011682 | 344 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 | 345 | |
2bfb2b75 | 346 | n_hdlc_send_frames(n_hdlc, tty); |
1da177e4 LT |
347 | } /* end of n_hdlc_tty_wakeup() */ |
348 | ||
1da177e4 LT |
349 | /** |
350 | * n_hdlc_tty_receive - Called by tty driver when receive data is available | |
351 | * @tty - pointer to tty instance data | |
352 | * @data - pointer to received data | |
353 | * @flags - pointer to flags for data | |
354 | * @count - count of received data in bytes | |
355 | * | |
356 | * Called by tty low level driver when receive data is available. Data is | |
357 | * interpreted as one HDLC frame. | |
358 | */ | |
55db4c64 LT |
359 | static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data, |
360 | char *flags, int count) | |
1da177e4 | 361 | { |
75011682 | 362 | register struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 LT |
363 | register struct n_hdlc_buf *buf; |
364 | ||
b18d1c2e | 365 | pr_debug("%s() called count=%d\n", __func__, count); |
f3c2e277 | 366 | |
1da177e4 LT |
367 | /* verify line is using HDLC discipline */ |
368 | if (n_hdlc->magic != HDLC_MAGIC) { | |
b18d1c2e | 369 | pr_err("line not using HDLC discipline\n"); |
55db4c64 | 370 | return; |
1da177e4 | 371 | } |
43741e9b | 372 | |
1283c721 | 373 | if (count > maxframe) { |
b18d1c2e | 374 | pr_debug("rx count>maxframesize, data discarded\n"); |
55db4c64 | 375 | return; |
1da177e4 LT |
376 | } |
377 | ||
43741e9b | 378 | /* get a free HDLC buffer */ |
1da177e4 LT |
379 | buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list); |
380 | if (!buf) { | |
80967ff2 JS |
381 | /* |
382 | * no buffers in free list, attempt to allocate another rx | |
383 | * buffer unless the maximum count has been reached | |
384 | */ | |
1da177e4 | 385 | if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT) |
85f4c951 GS |
386 | buf = kmalloc(struct_size(buf, buf, maxframe), |
387 | GFP_ATOMIC); | |
1da177e4 | 388 | } |
43741e9b | 389 | |
1da177e4 | 390 | if (!buf) { |
b18d1c2e | 391 | pr_debug("no more rx buffers, data discarded\n"); |
55db4c64 | 392 | return; |
1da177e4 | 393 | } |
43741e9b | 394 | |
1da177e4 | 395 | /* copy received data to HDLC buffer */ |
8d79bb5c | 396 | memcpy(buf->buf, data, count); |
1283c721 | 397 | buf->count = count; |
1da177e4 LT |
398 | |
399 | /* add HDLC buffer to list of received frames */ | |
400 | n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf); | |
43741e9b | 401 | |
1da177e4 | 402 | /* wake up any blocked reads and perform async signalling */ |
2bfb2b75 | 403 | wake_up_interruptible(&tty->read_wait); |
df6de639 JS |
404 | if (tty->fasync != NULL) |
405 | kill_fasync(&tty->fasync, SIGIO, POLL_IN); | |
1da177e4 LT |
406 | |
407 | } /* end of n_hdlc_tty_receive() */ | |
408 | ||
409 | /** | |
4a4efbde | 410 | * n_hdlc_tty_read - Called to retrieve one frame of data (if available) |
1da177e4 LT |
411 | * @tty - pointer to tty instance data |
412 | * @file - pointer to open file object | |
413 | * @buf - pointer to returned data buffer | |
414 | * @nr - size of returned data buffer | |
43741e9b | 415 | * |
1da177e4 LT |
416 | * Returns the number of bytes returned or error code. |
417 | */ | |
418 | static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, | |
419 | __u8 __user *buf, size_t nr) | |
420 | { | |
75011682 | 421 | struct n_hdlc *n_hdlc = tty->disc_data; |
1035b63d | 422 | int ret = 0; |
1da177e4 | 423 | struct n_hdlc_buf *rbuf; |
1035b63d | 424 | DECLARE_WAITQUEUE(wait, current); |
1da177e4 | 425 | |
1035b63d | 426 | add_wait_queue(&tty->read_wait, &wait); |
04f378b1 | 427 | |
1da177e4 | 428 | for (;;) { |
0f40fbbc | 429 | if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { |
1035b63d PF |
430 | ret = -EIO; |
431 | break; | |
04f378b1 | 432 | } |
1035b63d PF |
433 | if (tty_hung_up_p(file)) |
434 | break; | |
1da177e4 | 435 | |
1035b63d | 436 | set_current_state(TASK_INTERRUPTIBLE); |
1da177e4 LT |
437 | |
438 | rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list); | |
1035b63d PF |
439 | if (rbuf) { |
440 | if (rbuf->count > nr) { | |
441 | /* too large for caller's buffer */ | |
442 | ret = -EOVERFLOW; | |
443 | } else { | |
fc01d8c6 | 444 | __set_current_state(TASK_RUNNING); |
1035b63d PF |
445 | if (copy_to_user(buf, rbuf->buf, rbuf->count)) |
446 | ret = -EFAULT; | |
447 | else | |
448 | ret = rbuf->count; | |
449 | } | |
450 | ||
451 | if (n_hdlc->rx_free_buf_list.count > | |
452 | DEFAULT_RX_BUF_COUNT) | |
453 | kfree(rbuf); | |
454 | else | |
455 | n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf); | |
1da177e4 | 456 | break; |
1035b63d | 457 | } |
43741e9b | 458 | |
1da177e4 | 459 | /* no data */ |
c96cf923 | 460 | if (tty_io_nonblock(tty, file)) { |
1035b63d PF |
461 | ret = -EAGAIN; |
462 | break; | |
04f378b1 | 463 | } |
1035b63d PF |
464 | |
465 | schedule(); | |
466 | ||
04f378b1 | 467 | if (signal_pending(current)) { |
1035b63d PF |
468 | ret = -EINTR; |
469 | break; | |
04f378b1 | 470 | } |
1da177e4 | 471 | } |
1035b63d PF |
472 | |
473 | remove_wait_queue(&tty->read_wait, &wait); | |
474 | __set_current_state(TASK_RUNNING); | |
475 | ||
1da177e4 | 476 | return ret; |
43741e9b | 477 | |
1da177e4 LT |
478 | } /* end of n_hdlc_tty_read() */ |
479 | ||
480 | /** | |
481 | * n_hdlc_tty_write - write a single frame of data to device | |
482 | * @tty - pointer to associated tty device instance data | |
483 | * @file - pointer to file object data | |
484 | * @data - pointer to transmit data (one frame) | |
485 | * @count - size of transmit frame in bytes | |
43741e9b | 486 | * |
1da177e4 LT |
487 | * Returns the number of bytes written (or error code). |
488 | */ | |
489 | static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, | |
490 | const unsigned char *data, size_t count) | |
491 | { | |
75011682 | 492 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 LT |
493 | int error = 0; |
494 | DECLARE_WAITQUEUE(wait, current); | |
495 | struct n_hdlc_buf *tbuf; | |
496 | ||
b18d1c2e | 497 | pr_debug("%s() called count=%zd\n", __func__, count); |
f3c2e277 | 498 | |
1da177e4 LT |
499 | if (n_hdlc->magic != HDLC_MAGIC) |
500 | return -EIO; | |
501 | ||
502 | /* verify frame size */ | |
1283c721 | 503 | if (count > maxframe) { |
f3c2e277 JS |
504 | pr_debug("%s: truncating user packet from %zu to %d\n", |
505 | __func__, count, maxframe); | |
1da177e4 LT |
506 | count = maxframe; |
507 | } | |
43741e9b | 508 | |
1da177e4 | 509 | add_wait_queue(&tty->write_wait, &wait); |
1035b63d PF |
510 | |
511 | for (;;) { | |
512 | set_current_state(TASK_INTERRUPTIBLE); | |
43741e9b | 513 | |
1035b63d PF |
514 | tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list); |
515 | if (tbuf) | |
516 | break; | |
517 | ||
c96cf923 | 518 | if (tty_io_nonblock(tty, file)) { |
c72f527c PF |
519 | error = -EAGAIN; |
520 | break; | |
521 | } | |
1da177e4 | 522 | schedule(); |
844cc5f9 | 523 | |
1da177e4 LT |
524 | if (signal_pending(current)) { |
525 | error = -EINTR; | |
526 | break; | |
527 | } | |
528 | } | |
529 | ||
1035b63d | 530 | __set_current_state(TASK_RUNNING); |
1da177e4 LT |
531 | remove_wait_queue(&tty->write_wait, &wait); |
532 | ||
43741e9b | 533 | if (!error) { |
1da177e4 LT |
534 | /* Retrieve the user's buffer */ |
535 | memcpy(tbuf->buf, data, count); | |
536 | ||
537 | /* Send the data */ | |
538 | tbuf->count = error = count; | |
8d79bb5c JS |
539 | n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf); |
540 | n_hdlc_send_frames(n_hdlc, tty); | |
1da177e4 | 541 | } |
1035b63d | 542 | |
1da177e4 | 543 | return error; |
43741e9b | 544 | |
1da177e4 LT |
545 | } /* end of n_hdlc_tty_write() */ |
546 | ||
547 | /** | |
548 | * n_hdlc_tty_ioctl - process IOCTL system call for the tty device. | |
549 | * @tty - pointer to tty instance data | |
550 | * @file - pointer to open file object for device | |
551 | * @cmd - IOCTL command code | |
552 | * @arg - argument for IOCTL call (cmd dependent) | |
553 | * | |
554 | * Returns command dependent result. | |
555 | */ | |
556 | static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, | |
557 | unsigned int cmd, unsigned long arg) | |
558 | { | |
75011682 | 559 | struct n_hdlc *n_hdlc = tty->disc_data; |
1da177e4 LT |
560 | int error = 0; |
561 | int count; | |
562 | unsigned long flags; | |
82f2341c AP |
563 | struct n_hdlc_buf *buf = NULL; |
564 | ||
b18d1c2e | 565 | pr_debug("%s() called %d\n", __func__, cmd); |
f3c2e277 | 566 | |
1da177e4 | 567 | /* Verify the status of the device */ |
844cc5f9 | 568 | if (n_hdlc->magic != HDLC_MAGIC) |
1da177e4 LT |
569 | return -EBADF; |
570 | ||
571 | switch (cmd) { | |
572 | case FIONREAD: | |
573 | /* report count of read data available */ | |
574 | /* in next available frame (if any) */ | |
8d79bb5c | 575 | spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags); |
82f2341c AP |
576 | buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list, |
577 | struct n_hdlc_buf, list_item); | |
578 | if (buf) | |
579 | count = buf->count; | |
1da177e4 LT |
580 | else |
581 | count = 0; | |
8d79bb5c | 582 | spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags); |
1da177e4 LT |
583 | error = put_user(count, (int __user *)arg); |
584 | break; | |
585 | ||
586 | case TIOCOUTQ: | |
587 | /* get the pending tx byte count in the driver */ | |
f34d7a5b | 588 | count = tty_chars_in_buffer(tty); |
1da177e4 | 589 | /* add size of next output frame in queue */ |
8d79bb5c | 590 | spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); |
82f2341c AP |
591 | buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list, |
592 | struct n_hdlc_buf, list_item); | |
593 | if (buf) | |
594 | count += buf->count; | |
8d79bb5c | 595 | spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); |
1da177e4 LT |
596 | error = put_user(count, (int __user *)arg); |
597 | break; | |
598 | ||
be10eb75 PF |
599 | case TCFLSH: |
600 | switch (arg) { | |
601 | case TCIOFLUSH: | |
602 | case TCOFLUSH: | |
603 | flush_tx_queue(tty); | |
604 | } | |
361bf8a9 | 605 | /* fall through - to default */ |
be10eb75 | 606 | |
1da177e4 | 607 | default: |
47afa7a5 | 608 | error = n_tty_ioctl_helper(tty, file, cmd, arg); |
1da177e4 LT |
609 | break; |
610 | } | |
611 | return error; | |
43741e9b | 612 | |
1da177e4 LT |
613 | } /* end of n_hdlc_tty_ioctl() */ |
614 | ||
615 | /** | |
616 | * n_hdlc_tty_poll - TTY callback for poll system call | |
617 | * @tty - pointer to tty instance data | |
618 | * @filp - pointer to open file object for device | |
619 | * @poll_table - wait queue for operations | |
43741e9b | 620 | * |
1da177e4 LT |
621 | * Determine which operations (read/write) will not block and return info |
622 | * to caller. | |
623 | * Returns a bit mask containing info on which ops will not block. | |
624 | */ | |
afc9a42b | 625 | static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, |
1da177e4 LT |
626 | poll_table *wait) |
627 | { | |
75011682 | 628 | struct n_hdlc *n_hdlc = tty->disc_data; |
afc9a42b | 629 | __poll_t mask = 0; |
1da177e4 | 630 | |
844cc5f9 | 631 | if (n_hdlc->magic != HDLC_MAGIC) |
5f289514 JS |
632 | return 0; |
633 | ||
634 | /* | |
635 | * queue the current process into any wait queue that may awaken in the | |
636 | * future (read and write) | |
637 | */ | |
638 | poll_wait(filp, &tty->read_wait, wait); | |
639 | poll_wait(filp, &tty->write_wait, wait); | |
640 | ||
641 | /* set bits for operations that won't block */ | |
642 | if (!list_empty(&n_hdlc->rx_buf_list.list)) | |
643 | mask |= EPOLLIN | EPOLLRDNORM; /* readable */ | |
644 | if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) | |
645 | mask |= EPOLLHUP; | |
646 | if (tty_hung_up_p(filp)) | |
647 | mask |= EPOLLHUP; | |
648 | if (!tty_is_writelocked(tty) && | |
649 | !list_empty(&n_hdlc->tx_free_buf_list.list)) | |
650 | mask |= EPOLLOUT | EPOLLWRNORM; /* writable */ | |
651 | ||
1da177e4 LT |
652 | return mask; |
653 | } /* end of n_hdlc_tty_poll() */ | |
654 | ||
740708ab JS |
655 | static void n_hdlc_alloc_buf(struct n_hdlc_buf_list *list, unsigned int count, |
656 | const char *name) | |
657 | { | |
658 | struct n_hdlc_buf *buf; | |
659 | unsigned int i; | |
660 | ||
661 | for (i = 0; i < count; i++) { | |
662 | buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL); | |
663 | if (!buf) { | |
b18d1c2e JS |
664 | pr_debug("%s(), kmalloc() failed for %s buffer %u\n", |
665 | __func__, name, i); | |
740708ab JS |
666 | return; |
667 | } | |
668 | n_hdlc_buf_put(list, buf); | |
669 | } | |
670 | } | |
671 | ||
1da177e4 LT |
672 | /** |
673 | * n_hdlc_alloc - allocate an n_hdlc instance data structure | |
674 | * | |
675 | * Returns a pointer to newly created structure if success, otherwise %NULL | |
676 | */ | |
677 | static struct n_hdlc *n_hdlc_alloc(void) | |
678 | { | |
8e25f8ce | 679 | struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL); |
1da177e4 LT |
680 | |
681 | if (!n_hdlc) | |
682 | return NULL; | |
683 | ||
e9b736d8 JS |
684 | spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock); |
685 | spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock); | |
686 | spin_lock_init(&n_hdlc->rx_buf_list.spinlock); | |
687 | spin_lock_init(&n_hdlc->tx_buf_list.spinlock); | |
82f2341c AP |
688 | |
689 | INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list); | |
690 | INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list); | |
691 | INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list); | |
692 | INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list); | |
693 | ||
740708ab JS |
694 | n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx"); |
695 | n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx"); | |
696 | ||
1da177e4 LT |
697 | /* Initialize the control block */ |
698 | n_hdlc->magic = HDLC_MAGIC; | |
a1274b26 | 699 | |
1da177e4 | 700 | return n_hdlc; |
43741e9b | 701 | |
1da177e4 LT |
702 | } /* end of n_hdlc_alloc() */ |
703 | ||
82f2341c AP |
704 | /** |
705 | * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list | |
706 | * @buf_list - pointer to the buffer list | |
707 | * @buf - pointer to the buffer | |
708 | */ | |
709 | static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, | |
710 | struct n_hdlc_buf *buf) | |
711 | { | |
712 | unsigned long flags; | |
713 | ||
714 | spin_lock_irqsave(&buf_list->spinlock, flags); | |
715 | ||
716 | list_add(&buf->list_item, &buf_list->list); | |
717 | buf_list->count++; | |
718 | ||
719 | spin_unlock_irqrestore(&buf_list->spinlock, flags); | |
720 | } | |
721 | ||
1da177e4 LT |
722 | /** |
723 | * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list | |
82f2341c | 724 | * @buf_list - pointer to buffer list |
1da177e4 LT |
725 | * @buf - pointer to buffer |
726 | */ | |
82f2341c | 727 | static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list, |
1da177e4 LT |
728 | struct n_hdlc_buf *buf) |
729 | { | |
730 | unsigned long flags; | |
82f2341c AP |
731 | |
732 | spin_lock_irqsave(&buf_list->spinlock, flags); | |
733 | ||
734 | list_add_tail(&buf->list_item, &buf_list->list); | |
735 | buf_list->count++; | |
736 | ||
737 | spin_unlock_irqrestore(&buf_list->spinlock, flags); | |
1da177e4 LT |
738 | } /* end of n_hdlc_buf_put() */ |
739 | ||
740 | /** | |
741 | * n_hdlc_buf_get - remove and return an HDLC buffer from list | |
82f2341c | 742 | * @buf_list - pointer to HDLC buffer list |
43741e9b | 743 | * |
1da177e4 LT |
744 | * Remove and return an HDLC buffer from the head of the specified HDLC buffer |
745 | * list. | |
746 | * Returns a pointer to HDLC buffer if available, otherwise %NULL. | |
747 | */ | |
82f2341c | 748 | static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list) |
1da177e4 LT |
749 | { |
750 | unsigned long flags; | |
751 | struct n_hdlc_buf *buf; | |
82f2341c AP |
752 | |
753 | spin_lock_irqsave(&buf_list->spinlock, flags); | |
754 | ||
755 | buf = list_first_entry_or_null(&buf_list->list, | |
756 | struct n_hdlc_buf, list_item); | |
1da177e4 | 757 | if (buf) { |
82f2341c AP |
758 | list_del(&buf->list_item); |
759 | buf_list->count--; | |
1da177e4 | 760 | } |
82f2341c AP |
761 | |
762 | spin_unlock_irqrestore(&buf_list->spinlock, flags); | |
1da177e4 | 763 | return buf; |
1da177e4 LT |
764 | } /* end of n_hdlc_buf_get() */ |
765 | ||
edee649f JS |
766 | static struct tty_ldisc_ops n_hdlc_ldisc = { |
767 | .owner = THIS_MODULE, | |
768 | .magic = TTY_LDISC_MAGIC, | |
769 | .name = "hdlc", | |
770 | .open = n_hdlc_tty_open, | |
771 | .close = n_hdlc_tty_close, | |
772 | .read = n_hdlc_tty_read, | |
773 | .write = n_hdlc_tty_write, | |
774 | .ioctl = n_hdlc_tty_ioctl, | |
775 | .poll = n_hdlc_tty_poll, | |
776 | .receive_buf = n_hdlc_tty_receive, | |
777 | .write_wakeup = n_hdlc_tty_wakeup, | |
778 | .flush_buffer = flush_rx_queue, | |
779 | }; | |
780 | ||
1da177e4 LT |
781 | static int __init n_hdlc_init(void) |
782 | { | |
783 | int status; | |
784 | ||
785 | /* range check maxframe arg */ | |
c549725f | 786 | maxframe = clamp(maxframe, 4096, MAX_HDLC_FRAME_SIZE); |
1da177e4 | 787 | |
1da177e4 LT |
788 | status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc); |
789 | if (!status) | |
cda3756c JS |
790 | pr_info("N_HDLC line discipline registered with maxframe=%d\n", |
791 | maxframe); | |
1da177e4 | 792 | else |
cda3756c JS |
793 | pr_err("N_HDLC: error registering line discipline: %d\n", |
794 | status); | |
1da177e4 | 795 | |
1da177e4 | 796 | return status; |
43741e9b | 797 | |
1da177e4 LT |
798 | } /* end of init_module() */ |
799 | ||
1da177e4 LT |
800 | static void __exit n_hdlc_exit(void) |
801 | { | |
802 | /* Release tty registration of line discipline */ | |
64ccd715 | 803 | int status = tty_unregister_ldisc(N_HDLC); |
1da177e4 LT |
804 | |
805 | if (status) | |
aebe5fc3 JS |
806 | pr_err("N_HDLC: can't unregister line discipline (err = %d)\n", |
807 | status); | |
1da177e4 | 808 | else |
aebe5fc3 | 809 | pr_info("N_HDLC: line discipline unregistered\n"); |
1da177e4 LT |
810 | } |
811 | ||
812 | module_init(n_hdlc_init); | |
813 | module_exit(n_hdlc_exit); | |
814 | ||
815 | MODULE_LICENSE("GPL"); | |
816 | MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com"); | |
1da177e4 LT |
817 | module_param(maxframe, int, 0); |
818 | MODULE_ALIAS_LDISC(N_HDLC); |