sys/kern/tty_outq.c

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
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;			\
69 	to->to_nblocks++;						\
72 #define	TTYOUTQ_REMOVE_HEAD(to) do {					\
73 	to->to_firstblock = to->to_firstblock->tob_next;		\
74 	to->to_nblocks--;						\
77 #define	TTYOUTQ_RECYCLE(to, tob) do {					\
78 	if (to->to_quota <= to->to_nblocks)				\
81 		TTYOUTQ_INSERT_TAIL(to, tob);				\
85 ttyoutq_flush(struct ttyoutq *to)
88 	to->to_begin = 0;
89 	to->to_end = 0;
93 ttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t size)
97 	to->to_quota = howmany(size, TTYOUTQ_DATASIZE);
99 	while (to->to_quota > to->to_nblocks) {
102 		 * Add new blocks to the tail of the list.
105 		 * to allocate memory. This won't be a problem, because
107 		 * may cause us to allocate too many blocks, but this
114 		TTYOUTQ_INSERT_TAIL(to, tob);
119 ttyoutq_free(struct ttyoutq *to)
123 	ttyoutq_flush(to);
124 	to->to_quota = 0;
126 	while ((tob = to->to_firstblock) != NULL) {
127 		TTYOUTQ_REMOVE_HEAD(to);
131 	MPASS(to->to_nblocks == 0);
135 ttyoutq_read(struct ttyoutq *to, void *buf, size_t len)
144 		if (to->to_begin == to->to_end)
146 		tob = to->to_firstblock;
156 		cbegin = to->to_begin;
157 		cend = MIN(MIN(to->to_end, to->to_begin + len),
166 		if (cend == to->to_end) {
168 			to->to_begin = 0;
169 			to->to_end = 0;
172 			TTYOUTQ_REMOVE_HEAD(to);
173 			to->to_begin = 0;
174 			to->to_end -= TTYOUTQ_DATASIZE;
175 			TTYOUTQ_RECYCLE(to, tob);
178 			to->to_begin += clen;
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
196 ttyoutq_read_uio(struct ttyoutq *to, struct tty *tp, struct uio *uio)
205 		if (to->to_begin == to->to_end)
207 		tob = to->to_firstblock;
217 		cbegin = to->to_begin;
218 		cend = MIN(MIN(to->to_end, to->to_begin + uio->uio_resid),
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) {
234 			TTYOUTQ_REMOVE_HEAD(to);
235 			to->to_begin = 0;
236 			if (to->to_end <= TTYOUTQ_DATASIZE)
237 				to->to_end = 0;
239 				to->to_end -= TTYOUTQ_DATASIZE;
241 			/* Temporary unlock and copy the data to userspace. */
246 			/* Block can now be readded to the list. */
247 			TTYOUTQ_RECYCLE(to, tob);
255 			to->to_begin += clen;
256 			MPASS(to->to_begin < TTYOUTQ_DATASIZE);
258 			/* Temporary unlock and copy the data to userspace. */
272 ttyoutq_write(struct ttyoutq *to, const void *buf, size_t nbytes)
280 		boff = to->to_end % TTYOUTQ_DATASIZE;
282 		if (to->to_end == 0) {
284 			MPASS(to->to_begin == 0);
285 			tob = to->to_firstblock;
290 			to->to_lastblock = tob;
293 			tob = to->to_lastblock->tob_next;
298 			to->to_lastblock = tob;
300 			tob = to->to_lastblock;
310 		to->to_end += l;
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);