2 * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
5 * Portions of this software were developed under sponsorship from Snow
6 * B.V., the Netherlands.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD$");
33 #include <sys/param.h>
34 #include <sys/kernel.h>
36 #include <sys/queue.h>
37 #include <sys/systm.h>
44 * TTY output queue buffering.
46 * The previous design of the TTY layer offered the so-called clists.
47 * These clists were used for both the input queues and the output
48 * queue. We don't use certain features on the output side, like quoting
49 * bits for parity marking and such. This mechanism is similar to the
50 * old clists, but only contains the features we need to buffer the
54 struct ttyoutq_block
{
55 struct ttyoutq_block
*tob_next
;
56 char tob_data
[TTYOUTQ_DATASIZE
];
59 static uma_zone_t ttyoutq_zone
;
61 #define TTYOUTQ_INSERT_TAIL(to, tob) do { \
62 if (to->to_end == 0) { \
63 tob->tob_next = to->to_firstblock; \
64 to->to_firstblock = tob; \
66 tob->tob_next = to->to_lastblock->tob_next; \
67 to->to_lastblock->tob_next = tob; \
72 #define TTYOUTQ_REMOVE_HEAD(to) do { \
73 to->to_firstblock = to->to_firstblock->tob_next; \
77 #define TTYOUTQ_RECYCLE(to, tob) do { \
78 if (to->to_quota <= to->to_nblocks) \
79 uma_zfree(ttyoutq_zone, tob); \
81 TTYOUTQ_INSERT_TAIL(to, tob); \
85 ttyoutq_flush(struct ttyoutq
*to
)
93 ttyoutq_setsize(struct ttyoutq
*to
, struct tty
*tp
, size_t size
)
95 struct ttyoutq_block
*tob
;
97 to
->to_quota
= howmany(size
, TTYOUTQ_DATASIZE
);
99 while (to
->to_quota
> to
->to_nblocks
) {
101 * List is getting bigger.
102 * Add new blocks to the tail of the list.
104 * We must unlock the TTY temporarily, because we need
105 * to allocate memory. This won't be a problem, because
106 * in the worst case, another thread ends up here, which
107 * may cause us to allocate too many blocks, but this
108 * will be caught by the loop below.
111 tob
= uma_zalloc(ttyoutq_zone
, M_WAITOK
);
114 TTYOUTQ_INSERT_TAIL(to
, tob
);
119 ttyoutq_free(struct ttyoutq
*to
)
121 struct ttyoutq_block
*tob
;
126 while ((tob
= to
->to_firstblock
) != NULL
) {
127 TTYOUTQ_REMOVE_HEAD(to
);
128 uma_zfree(ttyoutq_zone
, tob
);
131 MPASS(to
->to_nblocks
== 0);
135 ttyoutq_read(struct ttyoutq
*to
, void *buf
, size_t len
)
140 struct ttyoutq_block
*tob
;
141 size_t cbegin
, cend
, clen
;
143 /* See if there still is data. */
144 if (to
->to_begin
== to
->to_end
)
146 tob
= to
->to_firstblock
;
151 * The end address should be the lowest of these three:
152 * - The write pointer
153 * - The blocksize - we can't read beyond the block
154 * - The end address if we could perform the full read
156 cbegin
= to
->to_begin
;
157 cend
= MIN(MIN(to
->to_end
, to
->to_begin
+ len
),
159 clen
= cend
- cbegin
;
161 /* Copy the data out of the buffers. */
162 memcpy(cbuf
, tob
->tob_data
+ cbegin
, clen
);
166 if (cend
== to
->to_end
) {
167 /* Read the complete queue. */
170 } else if (cend
== TTYOUTQ_DATASIZE
) {
171 /* Read the block until the end. */
172 TTYOUTQ_REMOVE_HEAD(to
);
174 to
->to_end
-= TTYOUTQ_DATASIZE
;
175 TTYOUTQ_RECYCLE(to
, tob
);
177 /* Read the block partially. */
178 to
->to_begin
+= clen
;
182 return (cbuf
- (char *)buf
);
186 * An optimized version of ttyoutq_read() which can be used in pseudo
187 * TTY drivers to directly copy data from the outq to userspace, instead
190 * We can only copy data directly if we need to read the entire block
191 * back to the user, because we temporarily remove the block from the
192 * queue. Otherwise we need to copy it to a temporary buffer first, to
193 * make sure data remains in the correct order.
196 ttyoutq_read_uio(struct ttyoutq
*to
, struct tty
*tp
, struct uio
*uio
)
199 while (uio
->uio_resid
> 0) {
201 struct ttyoutq_block
*tob
;
202 size_t cbegin
, cend
, clen
;
204 /* See if there still is data. */
205 if (to
->to_begin
== to
->to_end
)
207 tob
= to
->to_firstblock
;
212 * The end address should be the lowest of these three:
213 * - The write pointer
214 * - The blocksize - we can't read beyond the block
215 * - The end address if we could perform the full read
217 cbegin
= to
->to_begin
;
218 cend
= MIN(MIN(to
->to_end
, to
->to_begin
+ uio
->uio_resid
),
220 clen
= cend
- cbegin
;
223 * We can prevent buffering in some cases:
224 * - We need to read the block until the end.
225 * - We don't need to read the block until the end, but
226 * there is no data beyond it, which allows us to move
227 * the write pointer to a new block.
229 if (cend
== TTYOUTQ_DATASIZE
|| cend
== to
->to_end
) {
231 * Fast path: zero copy. Remove the first block,
232 * so we can unlock the TTY temporarily.
234 TTYOUTQ_REMOVE_HEAD(to
);
236 if (to
->to_end
<= TTYOUTQ_DATASIZE
)
239 to
->to_end
-= TTYOUTQ_DATASIZE
;
241 /* Temporary unlock and copy the data to userspace. */
243 error
= uiomove(tob
->tob_data
+ cbegin
, clen
, uio
);
246 /* Block can now be readded to the list. */
247 TTYOUTQ_RECYCLE(to
, tob
);
249 char ob
[TTYOUTQ_DATASIZE
- 1];
252 * Slow path: store data in a temporary buffer.
254 memcpy(ob
, tob
->tob_data
+ cbegin
, clen
);
255 to
->to_begin
+= clen
;
256 MPASS(to
->to_begin
< TTYOUTQ_DATASIZE
);
258 /* Temporary unlock and copy the data to userspace. */
260 error
= uiomove(ob
, clen
, uio
);
272 ttyoutq_write(struct ttyoutq
*to
, const void *buf
, size_t nbytes
)
274 const char *cbuf
= buf
;
275 struct ttyoutq_block
*tob
;
280 boff
= to
->to_end
% TTYOUTQ_DATASIZE
;
282 if (to
->to_end
== 0) {
283 /* First time we're being used or drained. */
284 MPASS(to
->to_begin
== 0);
285 tob
= to
->to_firstblock
;
287 /* Queue has no blocks. */
290 to
->to_lastblock
= tob
;
291 } else if (boff
== 0) {
292 /* We reached the end of this block on last write. */
293 tob
= to
->to_lastblock
->tob_next
;
295 /* We've reached the watermark. */
298 to
->to_lastblock
= tob
;
300 tob
= to
->to_lastblock
;
303 /* Don't copy more than was requested. */
304 l
= MIN(nbytes
, TTYOUTQ_DATASIZE
- boff
);
306 memcpy(tob
->tob_data
+ boff
, cbuf
, l
);
313 return (cbuf
- (const char *)buf
);
317 ttyoutq_write_nofrag(struct ttyoutq
*to
, const void *buf
, size_t nbytes
)
321 if (ttyoutq_bytesleft(to
) < nbytes
)
324 /* We should always be able to write it back. */
325 ret
= ttyoutq_write(to
, buf
, nbytes
);
326 MPASS(ret
== nbytes
);
332 ttyoutq_startup(void *dummy
)
335 ttyoutq_zone
= uma_zcreate("ttyoutq", sizeof(struct ttyoutq_block
),
336 NULL
, NULL
, NULL
, NULL
, UMA_ALIGN_PTR
, 0);
339 SYSINIT(ttyoutq
, SI_SUB_DRIVERS
, SI_ORDER_FIRST
, ttyoutq_startup
, NULL
);