[PATCH] devfs: Remove devfs_mk_dir() function from the kernel tree
[linux-2.6.git] / drivers / char / pty.c
1 /*
2  *  linux/drivers/char/pty.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  *
6  *  Added support for a Unix98-style ptmx device.
7  *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
8  *  Added TTY_DO_WRITE_WAKEUP to enable n_tty to send POLL_OUT to
9  *      waiting writers -- Sapan Bhatia <sapan@corewars.org>
10  *
11  *
12  */
13
14 #include <linux/config.h>
15 #include <linux/module.h>       /* For EXPORT_SYMBOL */
16
17 #include <linux/errno.h>
18 #include <linux/sched.h>
19 #include <linux/interrupt.h>
20 #include <linux/tty.h>
21 #include <linux/tty_flip.h>
22 #include <linux/fcntl.h>
23 #include <linux/string.h>
24 #include <linux/major.h>
25 #include <linux/mm.h>
26 #include <linux/init.h>
27 #include <linux/devfs_fs_kernel.h>
28 #include <linux/sysctl.h>
29
30 #include <asm/uaccess.h>
31 #include <asm/system.h>
32 #include <linux/bitops.h>
33 #include <linux/devpts_fs.h>
34
35 /* These are global because they are accessed in tty_io.c */
36 #ifdef CONFIG_UNIX98_PTYS
37 struct tty_driver *ptm_driver;
38 static struct tty_driver *pts_driver;
39 #endif
40
41 static void pty_close(struct tty_struct * tty, struct file * filp)
42 {
43         if (!tty)
44                 return;
45         if (tty->driver->subtype == PTY_TYPE_MASTER) {
46                 if (tty->count > 1)
47                         printk("master pty_close: count = %d!!\n", tty->count);
48         } else {
49                 if (tty->count > 2)
50                         return;
51         }
52         wake_up_interruptible(&tty->read_wait);
53         wake_up_interruptible(&tty->write_wait);
54         tty->packet = 0;
55         if (!tty->link)
56                 return;
57         tty->link->packet = 0;
58         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
59         wake_up_interruptible(&tty->link->read_wait);
60         wake_up_interruptible(&tty->link->write_wait);
61         if (tty->driver->subtype == PTY_TYPE_MASTER) {
62                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
63 #ifdef CONFIG_UNIX98_PTYS
64                 if (tty->driver == ptm_driver)
65                         devpts_pty_kill(tty->index);
66 #endif
67                 tty_vhangup(tty->link);
68         }
69 }
70
71 /*
72  * The unthrottle routine is called by the line discipline to signal
73  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
74  * flag is always set, to force the line discipline to always call the
75  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE 
76  * characters in the queue.  This is necessary since each time this
77  * happens, we need to wake up any sleeping processes that could be
78  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
79  * for the pty buffer to be drained.
80  */
81 static void pty_unthrottle(struct tty_struct * tty)
82 {
83         struct tty_struct *o_tty = tty->link;
84
85         if (!o_tty)
86                 return;
87
88         tty_wakeup(o_tty);
89         set_bit(TTY_THROTTLED, &tty->flags);
90 }
91
92 /*
93  * WSH 05/24/97: modified to 
94  *   (1) use space in tty->flip instead of a shared temp buffer
95  *       The flip buffers aren't being used for a pty, so there's lots
96  *       of space available.  The buffer is protected by a per-pty
97  *       semaphore that should almost never come under contention.
98  *   (2) avoid redundant copying for cases where count >> receive_room
99  * N.B. Calls from user space may now return an error code instead of
100  * a count.
101  *
102  * FIXME: Our pty_write method is called with our ldisc lock held but
103  * not our partners. We can't just take the other one blindly without
104  * risking deadlocks.  There is also the small matter of TTY_DONT_FLIP
105  */
106 static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count)
107 {
108         struct tty_struct *to = tty->link;
109         int     c;
110
111         if (!to || tty->stopped)
112                 return 0;
113
114         c = to->receive_room;
115         if (c > count)
116                 c = count;
117         to->ldisc.receive_buf(to, buf, NULL, c);
118         
119         return c;
120 }
121
122 static int pty_write_room(struct tty_struct *tty)
123 {
124         struct tty_struct *to = tty->link;
125
126         if (!to || tty->stopped)
127                 return 0;
128
129         return to->receive_room;
130 }
131
132 /*
133  *      WSH 05/24/97:  Modified for asymmetric MASTER/SLAVE behavior
134  *      The chars_in_buffer() value is used by the ldisc select() function 
135  *      to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
136  *      The pty driver chars_in_buffer() Master/Slave must behave differently:
137  *
138  *      The Master side needs to allow typed-ahead commands to accumulate
139  *      while being canonicalized, so we report "our buffer" as empty until
140  *      some threshold is reached, and then report the count. (Any count >
141  *      WAKEUP_CHARS is regarded by select() as "full".)  To avoid deadlock 
142  *      the count returned must be 0 if no canonical data is available to be 
143  *      read. (The N_TTY ldisc.chars_in_buffer now knows this.)
144  *  
145  *      The Slave side passes all characters in raw mode to the Master side's
146  *      buffer where they can be read immediately, so in this case we can
147  *      return the true count in the buffer.
148  */
149 static int pty_chars_in_buffer(struct tty_struct *tty)
150 {
151         struct tty_struct *to = tty->link;
152         int count;
153
154         /* We should get the line discipline lock for "tty->link" */
155         if (!to || !to->ldisc.chars_in_buffer)
156                 return 0;
157
158         /* The ldisc must report 0 if no characters available to be read */
159         count = to->ldisc.chars_in_buffer(to);
160
161         if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
162
163         /* Master side driver ... if the other side's read buffer is less than 
164          * half full, return 0 to allow writers to proceed; otherwise return
165          * the count.  This leaves a comfortable margin to avoid overflow, 
166          * and still allows half a buffer's worth of typed-ahead commands.
167          */
168         return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);
169 }
170
171 /* Set the lock flag on a pty */
172 static int pty_set_lock(struct tty_struct *tty, int __user * arg)
173 {
174         int val;
175         if (get_user(val,arg))
176                 return -EFAULT;
177         if (val)
178                 set_bit(TTY_PTY_LOCK, &tty->flags);
179         else
180                 clear_bit(TTY_PTY_LOCK, &tty->flags);
181         return 0;
182 }
183
184 static void pty_flush_buffer(struct tty_struct *tty)
185 {
186         struct tty_struct *to = tty->link;
187         
188         if (!to)
189                 return;
190         
191         if (to->ldisc.flush_buffer)
192                 to->ldisc.flush_buffer(to);
193         
194         if (to->packet) {
195                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
196                 wake_up_interruptible(&to->read_wait);
197         }
198 }
199
200 static int pty_open(struct tty_struct *tty, struct file * filp)
201 {
202         int     retval = -ENODEV;
203
204         if (!tty || !tty->link)
205                 goto out;
206
207         retval = -EIO;
208         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
209                 goto out;
210         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
211                 goto out;
212         if (tty->link->count != 1)
213                 goto out;
214
215         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
216         set_bit(TTY_THROTTLED, &tty->flags);
217         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
218         retval = 0;
219 out:
220         return retval;
221 }
222
223 static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios)
224 {
225         tty->termios->c_cflag &= ~(CSIZE | PARENB);
226         tty->termios->c_cflag |= (CS8 | CREAD);
227 }
228
229 static struct tty_operations pty_ops = {
230         .open = pty_open,
231         .close = pty_close,
232         .write = pty_write,
233         .write_room = pty_write_room,
234         .flush_buffer = pty_flush_buffer,
235         .chars_in_buffer = pty_chars_in_buffer,
236         .unthrottle = pty_unthrottle,
237         .set_termios = pty_set_termios,
238 };
239
240 /* Traditional BSD devices */
241 #ifdef CONFIG_LEGACY_PTYS
242 static struct tty_driver *pty_driver, *pty_slave_driver;
243
244 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
245                          unsigned int cmd, unsigned long arg)
246 {
247         switch (cmd) {
248         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
249                 return pty_set_lock(tty, (int __user *) arg);
250         }
251         return -ENOIOCTLCMD;
252 }
253
254 static void __init legacy_pty_init(void)
255 {
256
257         pty_driver = alloc_tty_driver(NR_PTYS);
258         if (!pty_driver)
259                 panic("Couldn't allocate pty driver");
260
261         pty_slave_driver = alloc_tty_driver(NR_PTYS);
262         if (!pty_slave_driver)
263                 panic("Couldn't allocate pty slave driver");
264
265         pty_driver->owner = THIS_MODULE;
266         pty_driver->driver_name = "pty_master";
267         pty_driver->name = "pty";
268         pty_driver->devfs_name = "pty/m";
269         pty_driver->major = PTY_MASTER_MAJOR;
270         pty_driver->minor_start = 0;
271         pty_driver->type = TTY_DRIVER_TYPE_PTY;
272         pty_driver->subtype = PTY_TYPE_MASTER;
273         pty_driver->init_termios = tty_std_termios;
274         pty_driver->init_termios.c_iflag = 0;
275         pty_driver->init_termios.c_oflag = 0;
276         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
277         pty_driver->init_termios.c_lflag = 0;
278         pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
279         pty_driver->other = pty_slave_driver;
280         tty_set_operations(pty_driver, &pty_ops);
281         pty_driver->ioctl = pty_bsd_ioctl;
282
283         pty_slave_driver->owner = THIS_MODULE;
284         pty_slave_driver->driver_name = "pty_slave";
285         pty_slave_driver->name = "ttyp";
286         pty_slave_driver->devfs_name = "pty/s";
287         pty_slave_driver->major = PTY_SLAVE_MAJOR;
288         pty_slave_driver->minor_start = 0;
289         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
290         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
291         pty_slave_driver->init_termios = tty_std_termios;
292         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
293         pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
294                                         TTY_DRIVER_REAL_RAW;
295         pty_slave_driver->other = pty_driver;
296         tty_set_operations(pty_slave_driver, &pty_ops);
297
298         if (tty_register_driver(pty_driver))
299                 panic("Couldn't register pty driver");
300         if (tty_register_driver(pty_slave_driver))
301                 panic("Couldn't register pty slave driver");
302 }
303 #else
304 static inline void legacy_pty_init(void) { }
305 #endif
306
307 /* Unix98 devices */
308 #ifdef CONFIG_UNIX98_PTYS
309 /*
310  * sysctl support for setting limits on the number of Unix98 ptys allocated.
311  * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
312  */
313 int pty_limit = NR_UNIX98_PTY_DEFAULT;
314 static int pty_limit_min = 0;
315 static int pty_limit_max = NR_UNIX98_PTY_MAX;
316
317 ctl_table pty_table[] = {
318         {
319                 .ctl_name       = PTY_MAX,
320                 .procname       = "max",
321                 .maxlen         = sizeof(int),
322                 .mode           = 0644,
323                 .data           = &pty_limit,
324                 .proc_handler   = &proc_dointvec_minmax,
325                 .strategy       = &sysctl_intvec,
326                 .extra1         = &pty_limit_min,
327                 .extra2         = &pty_limit_max,
328         }, {
329                 .ctl_name       = PTY_NR,
330                 .procname       = "nr",
331                 .maxlen         = sizeof(int),
332                 .mode           = 0444,
333                 .proc_handler   = &proc_dointvec,
334         }, {
335                 .ctl_name       = 0
336         }
337 };
338
339 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
340                             unsigned int cmd, unsigned long arg)
341 {
342         switch (cmd) {
343         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
344                 return pty_set_lock(tty, (int __user *)arg);
345         case TIOCGPTN: /* Get PT Number */
346                 return put_user(tty->index, (unsigned int __user *)arg);
347         }
348
349         return -ENOIOCTLCMD;
350 }
351
352 static void __init unix98_pty_init(void)
353 {
354         ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
355         if (!ptm_driver)
356                 panic("Couldn't allocate Unix98 ptm driver");
357         pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
358         if (!pts_driver)
359                 panic("Couldn't allocate Unix98 pts driver");
360
361         ptm_driver->owner = THIS_MODULE;
362         ptm_driver->driver_name = "pty_master";
363         ptm_driver->name = "ptm";
364         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
365         ptm_driver->minor_start = 0;
366         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
367         ptm_driver->subtype = PTY_TYPE_MASTER;
368         ptm_driver->init_termios = tty_std_termios;
369         ptm_driver->init_termios.c_iflag = 0;
370         ptm_driver->init_termios.c_oflag = 0;
371         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
372         ptm_driver->init_termios.c_lflag = 0;
373         ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
374                 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
375         ptm_driver->other = pts_driver;
376         tty_set_operations(ptm_driver, &pty_ops);
377         ptm_driver->ioctl = pty_unix98_ioctl;
378
379         pts_driver->owner = THIS_MODULE;
380         pts_driver->driver_name = "pty_slave";
381         pts_driver->name = "pts";
382         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
383         pts_driver->minor_start = 0;
384         pts_driver->type = TTY_DRIVER_TYPE_PTY;
385         pts_driver->subtype = PTY_TYPE_SLAVE;
386         pts_driver->init_termios = tty_std_termios;
387         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
388         pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
389                 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
390         pts_driver->other = ptm_driver;
391         tty_set_operations(pts_driver, &pty_ops);
392         
393         if (tty_register_driver(ptm_driver))
394                 panic("Couldn't register Unix98 ptm driver");
395         if (tty_register_driver(pts_driver))
396                 panic("Couldn't register Unix98 pts driver");
397
398         pty_table[1].data = &ptm_driver->refcount;
399 }
400 #else
401 static inline void unix98_pty_init(void) { }
402 #endif
403
404 static int __init pty_init(void)
405 {
406         legacy_pty_init();
407         unix98_pty_init();
408         return 0;
409 }
410 module_init(pty_init);