[net-next-2.6.git] / drivers / char / tty_buffer.c

/*
 * Tty buffer allocation management
 */

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/module.h>

/**
 *	tty_buffer_free_all		-	free buffers used by a tty
 *	@tty: tty to free from
 *
 *	Remove all the buffers pending on a tty whether queued with data
 *	or in the free ring. Must be called when the tty is no longer in use
 *
 *	Locking: none
 */

void tty_buffer_free_all(struct tty_struct *tty)
{
	struct tty_buffer *thead;
	while ((thead = tty->buf.head) != NULL) {
		tty->buf.head = thead->next;
		kfree(thead);
	}
	while ((thead = tty->buf.free) != NULL) {
		tty->buf.free = thead->next;
		kfree(thead);
	}
	tty->buf.tail = NULL;
	tty->buf.memory_used = 0;
}

/**
 *	tty_buffer_alloc	-	allocate a tty buffer
 *	@tty: tty device
 *	@size: desired size (characters)
 *
 *	Allocate a new tty buffer to hold the desired number of characters.
 *	Return NULL if out of memory or the allocation would exceed the
 *	per device queue
 *
 *	Locking: Caller must hold tty->buf.lock
 */

static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
{
	struct tty_buffer *p;

	if (tty->buf.memory_used + size > 65536)
		return NULL;
	p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
	if (p == NULL)
		return NULL;
	p->used = 0;
	p->size = size;
	p->next = NULL;
	p->commit = 0;
	p->read = 0;
	p->char_buf_ptr = (char *)(p->data);
	p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
	tty->buf.memory_used += size;
	return p;
}

/**
 *	tty_buffer_free		-	free a tty buffer
 *	@tty: tty owning the buffer
 *	@b: the buffer to free
 *
 *	Free a tty buffer, or add it to the free list according to our
 *	internal strategy
 *
 *	Locking: Caller must hold tty->buf.lock
 */

static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
{
	/* Dumb strategy for now - should keep some stats */
	tty->buf.memory_used -= b->size;
	WARN_ON(tty->buf.memory_used < 0);

	if (b->size >= 512)
		kfree(b);
	else {
		b->next = tty->buf.free;
		tty->buf.free = b;
	}
}

/**
 *	__tty_buffer_flush		-	flush full tty buffers
 *	@tty: tty to flush
 *
 *	flush all the buffers containing receive data. Caller must
 *	hold the buffer lock and must have ensured no parallel flush to
 *	ldisc is running.
 *
 *	Locking: Caller must hold tty->buf.lock
 */

static void __tty_buffer_flush(struct tty_struct *tty)
{
	struct tty_buffer *thead;

	while ((thead = tty->buf.head) != NULL) {
		tty->buf.head = thead->next;
		tty_buffer_free(tty, thead);
	}
	tty->buf.tail = NULL;
}

/**
 *	tty_buffer_flush		-	flush full tty buffers
 *	@tty: tty to flush
 *
 *	flush all the buffers containing receive data. If the buffer is
 *	being processed by flush_to_ldisc then we defer the processing
 *	to that function
 *
 *	Locking: none
 */

void tty_buffer_flush(struct tty_struct *tty)
{
	unsigned long flags;
	spin_lock_irqsave(&tty->buf.lock, flags);

	/* If the data is being pushed to the tty layer then we can't
	   process it here. Instead set a flag and the flush_to_ldisc
	   path will process the flush request before it exits */
	if (test_bit(TTY_FLUSHING, &tty->flags)) {
		set_bit(TTY_FLUSHPENDING, &tty->flags);
		spin_unlock_irqrestore(&tty->buf.lock, flags);
		wait_event(tty->read_wait,
				test_bit(TTY_FLUSHPENDING, &tty->flags) == 0);
		return;
	} else
		__tty_buffer_flush(tty);
	spin_unlock_irqrestore(&tty->buf.lock, flags);
}

/**
 *	tty_buffer_find		-	find a free tty buffer
 *	@tty: tty owning the buffer
 *	@size: characters wanted
 *
 *	Locate an existing suitable tty buffer or if we are lacking one then
 *	allocate a new one. We round our buffers off in 256 character chunks
 *	to get better allocation behaviour.
 *
 *	Locking: Caller must hold tty->buf.lock
 */

static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
{
	struct tty_buffer **tbh = &tty->buf.free;
	while ((*tbh) != NULL) {
		struct tty_buffer *t = *tbh;
		if (t->size >= size) {
			*tbh = t->next;
			t->next = NULL;
			t->used = 0;
			t->commit = 0;
			t->read = 0;
			tty->buf.memory_used += t->size;
			return t;
		}
		tbh = &((*tbh)->next);
	}
	/* Round the buffer size out */
	size = (size + 0xFF) & ~0xFF;
	return tty_buffer_alloc(tty, size);
	/* Should possibly check if this fails for the largest buffer we
	   have queued and recycle that ? */
}

/**
 *	tty_buffer_request_room		-	grow tty buffer if needed
 *	@tty: tty structure
 *	@size: size desired
 *
 *	Make at least size bytes of linear space available for the tty
 *	buffer. If we fail return the size we managed to find.
 *
 *	Locking: Takes tty->buf.lock
 */
int tty_buffer_request_room(struct tty_struct *tty, size_t size)
{
	struct tty_buffer *b, *n;
	int left;
	unsigned long flags;

	spin_lock_irqsave(&tty->buf.lock, flags);

	/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
	   remove this conditional if its worth it. This would be invisible
	   to the callers */
	if ((b = tty->buf.tail) != NULL)
		left = b->size - b->used;
	else
		left = 0;

	if (left < size) {
		/* This is the slow path - looking for new buffers to use */
		if ((n = tty_buffer_find(tty, size)) != NULL) {
			if (b != NULL) {
				b->next = n;
				b->commit = b->used;
			} else
				tty->buf.head = n;
			tty->buf.tail = n;
		} else
			size = left;
	}

	spin_unlock_irqrestore(&tty->buf.lock, flags);
	return size;
}
EXPORT_SYMBOL_GPL(tty_buffer_request_room);

/**
 *	tty_insert_flip_string	-	Add characters to the tty buffer
 *	@tty: tty structure
 *	@chars: characters
 *	@size: size
 *
 *	Queue a series of bytes to the tty buffering. All the characters
 *	passed are marked as without error. Returns the number added.
 *
 *	Locking: Called functions may take tty->buf.lock
 */

int tty_insert_flip_string(struct tty_struct *tty, const unsigned char *chars,
				size_t size)
{
	int copied = 0;
	do {
		int goal = min(size - copied, TTY_BUFFER_PAGE);
		int space = tty_buffer_request_room(tty, goal);
		struct tty_buffer *tb = tty->buf.tail;
		/* If there is no space then tb may be NULL */
		if (unlikely(space == 0))
			break;
		memcpy(tb->char_buf_ptr + tb->used, chars, space);
		memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
		tb->used += space;
		copied += space;
		chars += space;
		/* There is a small chance that we need to split the data over
		   several buffers. If this is the case we must loop */
	} while (unlikely(size > copied));
	return copied;
}
EXPORT_SYMBOL(tty_insert_flip_string);

/**
 *	tty_insert_flip_string_flags	-	Add characters to the tty buffer
 *	@tty: tty structure
 *	@chars: characters
 *	@flags: flag bytes
 *	@size: size
 *
 *	Queue a series of bytes to the tty buffering. For each character
 *	the flags array indicates the status of the character. Returns the
 *	number added.
 *
 *	Locking: Called functions may take tty->buf.lock
 */

int tty_insert_flip_string_flags(struct tty_struct *tty,
		const unsigned char *chars, const char *flags, size_t size)
{
	int copied = 0;
	do {
		int goal = min(size - copied, TTY_BUFFER_PAGE);
		int space = tty_buffer_request_room(tty, goal);
		struct tty_buffer *tb = tty->buf.tail;
		/* If there is no space then tb may be NULL */
		if (unlikely(space == 0))
			break;
		memcpy(tb->char_buf_ptr + tb->used, chars, space);
		memcpy(tb->flag_buf_ptr + tb->used, flags, space);
		tb->used += space;
		copied += space;
		chars += space;
		flags += space;
		/* There is a small chance that we need to split the data over
		   several buffers. If this is the case we must loop */
	} while (unlikely(size > copied));
	return copied;
}
EXPORT_SYMBOL(tty_insert_flip_string_flags);

/**
 *	tty_schedule_flip	-	push characters to ldisc
 *	@tty: tty to push from
 *
 *	Takes any pending buffers and transfers their ownership to the
 *	ldisc side of the queue. It then schedules those characters for
 *	processing by the line discipline.
 *
 *	Locking: Takes tty->buf.lock
 */

void tty_schedule_flip(struct tty_struct *tty)
{
	unsigned long flags;
	spin_lock_irqsave(&tty->buf.lock, flags);
	if (tty->buf.tail != NULL)
		tty->buf.tail->commit = tty->buf.tail->used;
	spin_unlock_irqrestore(&tty->buf.lock, flags);
	schedule_delayed_work(&tty->buf.work, 1);
}
EXPORT_SYMBOL(tty_schedule_flip);

/**
 *	tty_prepare_flip_string		-	make room for characters
 *	@tty: tty
 *	@chars: return pointer for character write area
 *	@size: desired size
 *
 *	Prepare a block of space in the buffer for data. Returns the length
 *	available and buffer pointer to the space which is now allocated and
 *	accounted for as ready for normal characters. This is used for drivers
 *	that need their own block copy routines into the buffer. There is no
 *	guarantee the buffer is a DMA target!
 *
 *	Locking: May call functions taking tty->buf.lock
 */

int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
								size_t size)
{
	int space = tty_buffer_request_room(tty, size);
	if (likely(space)) {
		struct tty_buffer *tb = tty->buf.tail;
		*chars = tb->char_buf_ptr + tb->used;
		memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
		tb->used += space;
	}
	return space;
}
EXPORT_SYMBOL_GPL(tty_prepare_flip_string);

/**
 *	tty_prepare_flip_string_flags	-	make room for characters
 *	@tty: tty
 *	@chars: return pointer for character write area
 *	@flags: return pointer for status flag write area
 *	@size: desired size
 *
 *	Prepare a block of space in the buffer for data. Returns the length
 *	available and buffer pointer to the space which is now allocated and
 *	accounted for as ready for characters. This is used for drivers
 *	that need their own block copy routines into the buffer. There is no
 *	guarantee the buffer is a DMA target!
 *
 *	Locking: May call functions taking tty->buf.lock
 */

int tty_prepare_flip_string_flags(struct tty_struct *tty,
			unsigned char **chars, char **flags, size_t size)
{
	int space = tty_buffer_request_room(tty, size);
	if (likely(space)) {
		struct tty_buffer *tb = tty->buf.tail;
		*chars = tb->char_buf_ptr + tb->used;
		*flags = tb->flag_buf_ptr + tb->used;
		tb->used += space;
	}
	return space;
}
EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);


/**
 *	flush_to_ldisc
 *	@work: tty structure passed from work queue.
 *
 *	This routine is called out of the software interrupt to flush data
 *	from the buffer chain to the line discipline.
 *
 *	Locking: holds tty->buf.lock to guard buffer list. Drops the lock
 *	while invoking the line discipline receive_buf method. The
 *	receive_buf method is single threaded for each tty instance.
 */

static void flush_to_ldisc(struct work_struct *work)
{
	struct tty_struct *tty =
		container_of(work, struct tty_struct, buf.work.work);
	unsigned long 	flags;
	struct tty_ldisc *disc;

	disc = tty_ldisc_ref(tty);
	if (disc == NULL)	/*  !TTY_LDISC */
		return;

	spin_lock_irqsave(&tty->buf.lock, flags);

	if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {
		struct tty_buffer *head;
		while ((head = tty->buf.head) != NULL) {
			int count;
			char *char_buf;
			unsigned char *flag_buf;

			count = head->commit - head->read;
			if (!count) {
				if (head->next == NULL)
					break;
				tty->buf.head = head->next;
				tty_buffer_free(tty, head);
				continue;
			}
			/* Ldisc or user is trying to flush the buffers
			   we are feeding to the ldisc, stop feeding the
			   line discipline as we want to empty the queue */
			if (test_bit(TTY_FLUSHPENDING, &tty->flags))
				break;
			if (!tty->receive_room) {
				schedule_delayed_work(&tty->buf.work, 1);
				break;
			}
			if (count > tty->receive_room)
				count = tty->receive_room;
			char_buf = head->char_buf_ptr + head->read;
			flag_buf = head->flag_buf_ptr + head->read;
			head->read += count;
			spin_unlock_irqrestore(&tty->buf.lock, flags);
			disc->ops->receive_buf(tty, char_buf,
							flag_buf, count);
			spin_lock_irqsave(&tty->buf.lock, flags);
		}
		clear_bit(TTY_FLUSHING, &tty->flags);
	}

	/* We may have a deferred request to flush the input buffer,
	   if so pull the chain under the lock and empty the queue */
	if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
		__tty_buffer_flush(tty);
		clear_bit(TTY_FLUSHPENDING, &tty->flags);
		wake_up(&tty->read_wait);
	}
	spin_unlock_irqrestore(&tty->buf.lock, flags);

	tty_ldisc_deref(disc);
}

/**
 *	tty_flush_to_ldisc
 *	@tty: tty to push
 *
 *	Push the terminal flip buffers to the line discipline.
 *
 *	Must not be called from IRQ context.
 */
void tty_flush_to_ldisc(struct tty_struct *tty)
{
	flush_delayed_work(&tty->buf.work);
}

/**
 *	tty_flip_buffer_push	-	terminal
 *	@tty: tty to push
 *
 *	Queue a push of the terminal flip buffers to the line discipline. This
 *	function must not be called from IRQ context if tty->low_latency is set.
 *
 *	In the event of the queue being busy for flipping the work will be
 *	held off and retried later.
 *
 *	Locking: tty buffer lock. Driver locks in low latency mode.
 */

void tty_flip_buffer_push(struct tty_struct *tty)
{
	unsigned long flags;
	spin_lock_irqsave(&tty->buf.lock, flags);
	if (tty->buf.tail != NULL)
		tty->buf.tail->commit = tty->buf.tail->used;
	spin_unlock_irqrestore(&tty->buf.lock, flags);

	if (tty->low_latency)
		flush_to_ldisc(&tty->buf.work.work);
	else
		schedule_delayed_work(&tty->buf.work, 1);
}
EXPORT_SYMBOL(tty_flip_buffer_push);

/**
 *	tty_buffer_init		-	prepare a tty buffer structure
 *	@tty: tty to initialise
 *
 *	Set up the initial state of the buffer management for a tty device.
 *	Must be called before the other tty buffer functions are used.
 *
 *	Locking: none
 */

void tty_buffer_init(struct tty_struct *tty)
{
	spin_lock_init(&tty->buf.lock);
	tty->buf.head = NULL;
	tty->buf.tail = NULL;
	tty->buf.free = NULL;
	tty->buf.memory_used = 0;
	INIT_DELAYED_WORK(&tty->buf.work, flush_to_ldisc);
}
Commit	Line	Data
e0495736 AC	1	/*
	2	* Tty buffer allocation management
	3	*/
	4
	5	#include <linux/types.h>
	6	#include <linux/errno.h>
	7	#include <linux/tty.h>
	8	#include <linux/tty_driver.h>
	9	#include <linux/tty_flip.h>
	10	#include <linux/timer.h>
	11	#include <linux/string.h>
	12	#include <linux/slab.h>
	13	#include <linux/sched.h>
	14	#include <linux/init.h>
	15	#include <linux/wait.h>
	16	#include <linux/bitops.h>
	17	#include <linux/delay.h>
	18	#include <linux/module.h>
	19
	20	/**
	21	* tty_buffer_free_all - free buffers used by a tty
	22	* @tty: tty to free from
	23	*
	24	* Remove all the buffers pending on a tty whether queued with data
	25	* or in the free ring. Must be called when the tty is no longer in use
	26	*
	27	* Locking: none
	28	*/
	29
	30	void tty_buffer_free_all(struct tty_struct *tty)
	31	{
	32	struct tty_buffer *thead;
	33	while ((thead = tty->buf.head) != NULL) {
	34	tty->buf.head = thead->next;
	35	kfree(thead);
	36	}
	37	while ((thead = tty->buf.free) != NULL) {
	38	tty->buf.free = thead->next;
	39	kfree(thead);
	40	}
	41	tty->buf.tail = NULL;
	42	tty->buf.memory_used = 0;
	43	}
	44
	45	/**
	46	* tty_buffer_alloc - allocate a tty buffer
	47	* @tty: tty device
	48	* @size: desired size (characters)
	49	*
	50	* Allocate a new tty buffer to hold the desired number of characters.
	51	* Return NULL if out of memory or the allocation would exceed the
	52	* per device queue
	53	*
	54	* Locking: Caller must hold tty->buf.lock
	55	*/
	56
	57	static struct tty_buffer tty_buffer_alloc(struct tty_struct tty, size_t size)
	58	{
	59	struct tty_buffer *p;
	60
	61	if (tty->buf.memory_used + size > 65536)
	62	return NULL;
	63	p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
	64	if (p == NULL)
65	return NULL;
66	p->used = 0;
67	p->size = size;
68	p->next = NULL;
69	p->commit = 0;
70	p->read = 0;
71	p->char_buf_ptr = (char *)(p->data);
72	p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
73	tty->buf.memory_used += size;
74	return p;
75	}
76
77	/**
78	* tty_buffer_free - free a tty buffer
79	* @tty: tty owning the buffer
80	* @b: the buffer to free
81	*
82	* Free a tty buffer, or add it to the free list according to our
83	* internal strategy
84	*
85	* Locking: Caller must hold tty->buf.lock
86	*/
87
88	static void tty_buffer_free(struct tty_struct tty, struct tty_buffer b)
89	{
90	/* Dumb strategy for now - should keep some stats */
91	tty->buf.memory_used -= b->size;
92	WARN_ON(tty->buf.memory_used < 0);
93
94	if (b->size >= 512)
95	kfree(b);
96	else {
97	b->next = tty->buf.free;
98	tty->buf.free = b;
99	}
100	}
101
102	/**
103	* __tty_buffer_flush - flush full tty buffers
104	* @tty: tty to flush
105	*
106	* flush all the buffers containing receive data. Caller must
107	* hold the buffer lock and must have ensured no parallel flush to
108	* ldisc is running.
109	*
110	* Locking: Caller must hold tty->buf.lock
111	*/
112
113	static void __tty_buffer_flush(struct tty_struct *tty)
114	{
115	struct tty_buffer *thead;
116
117	while ((thead = tty->buf.head) != NULL) {
118	tty->buf.head = thead->next;
119	tty_buffer_free(tty, thead);
120	}
121	tty->buf.tail = NULL;
122	}
123
124	/**
125	* tty_buffer_flush - flush full tty buffers
126	* @tty: tty to flush
127	*
128	* flush all the buffers containing receive data. If the buffer is
129	* being processed by flush_to_ldisc then we defer the processing
130	* to that function
131	*
132	* Locking: none
133	*/
134
135	void tty_buffer_flush(struct tty_struct *tty)
136	{
137	unsigned long flags;
138	spin_lock_irqsave(&tty->buf.lock, flags);
139
140	/* If the data is being pushed to the tty layer then we can't
141	process it here. Instead set a flag and the flush_to_ldisc
142	path will process the flush request before it exits */
143	if (test_bit(TTY_FLUSHING, &tty->flags)) {
144	set_bit(TTY_FLUSHPENDING, &tty->flags);
145	spin_unlock_irqrestore(&tty->buf.lock, flags);
146	wait_event(tty->read_wait,
147	test_bit(TTY_FLUSHPENDING, &tty->flags) == 0);
148	return;
149	} else
150	__tty_buffer_flush(tty);
151	spin_unlock_irqrestore(&tty->buf.lock, flags);
152	}
153
154	/**
155	* tty_buffer_find - find a free tty buffer
156	* @tty: tty owning the buffer
157	* @size: characters wanted
158	*
159	* Locate an existing suitable tty buffer or if we are lacking one then
160	* allocate a new one. We round our buffers off in 256 character chunks
161	* to get better allocation behaviour.
162	*
163	* Locking: Caller must hold tty->buf.lock
164	*/
165
166	static struct tty_buffer tty_buffer_find(struct tty_struct tty, size_t size)
167	{
168	struct tty_buffer **tbh = &tty->buf.free;
169	while ((*tbh) != NULL) {
170	struct tty_buffer t = tbh;
171	if (t->size >= size) {
172	*tbh = t->next;
173	t->next = NULL;
174	t->used = 0;
175	t->commit = 0;
176	t->read = 0;
177	tty->buf.memory_used += t->size;
178	return t;
179	}
180	tbh = &((*tbh)->next);
181	}
182	/* Round the buffer size out */
183	size = (size + 0xFF) & ~0xFF;
184	return tty_buffer_alloc(tty, size);
185	/* Should possibly check if this fails for the largest buffer we
186	have queued and recycle that ? */
187	}
188
189	/**
190	* tty_buffer_request_room - grow tty buffer if needed
191	* @tty: tty structure
192	* @size: size desired
193	*
194	* Make at least size bytes of linear space available for the tty
195	* buffer. If we fail return the size we managed to find.
196	*
197	* Locking: Takes tty->buf.lock
198	*/
199	int tty_buffer_request_room(struct tty_struct *tty, size_t size)
200	{
201	struct tty_buffer b, n;
202	int left;
203	unsigned long flags;
204
205	spin_lock_irqsave(&tty->buf.lock, flags);
206
207	/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
208	remove this conditional if its worth it. This would be invisible
209	to the callers */
210	if ((b = tty->buf.tail) != NULL)
211	left = b->size - b->used;
212	else
213	left = 0;
214
215	if (left < size) {
216	/* This is the slow path - looking for new buffers to use */
217	if ((n = tty_buffer_find(tty, size)) != NULL) {
218	if (b != NULL) {
219	b->next = n;
220	b->commit = b->used;
221	} else
222	tty->buf.head = n;
223	tty->buf.tail = n;
224	} else
225	size = left;
226	}
227
228	spin_unlock_irqrestore(&tty->buf.lock, flags);
229	return size;
230	}
231	EXPORT_SYMBOL_GPL(tty_buffer_request_room);
232
233	/**
234	* tty_insert_flip_string - Add characters to the tty buffer
235	* @tty: tty structure
236	* @chars: characters
237	* @size: size
238	*
239	* Queue a series of bytes to the tty buffering. All the characters
240	* passed are marked as without error. Returns the number added.
241	*
242	* Locking: Called functions may take tty->buf.lock
243	*/
244
245	int tty_insert_flip_string(struct tty_struct tty, const unsigned char chars,
246	size_t size)
247	{
248	int copied = 0;
249	do {
d9661adf AC	250	int goal = min(size - copied, TTY_BUFFER_PAGE);
d9661adf AC	251	int space = tty_buffer_request_room(tty, goal);
e0495736 AC	252	struct tty_buffer *tb = tty->buf.tail;
	253	/* If there is no space then tb may be NULL */
	254	if (unlikely(space == 0))
	255	break;
	256	memcpy(tb->char_buf_ptr + tb->used, chars, space);
	257	memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
	258	tb->used += space;
	259	copied += space;
	260	chars += space;
	261	/* There is a small chance that we need to split the data over
	262	several buffers. If this is the case we must loop */
	263	} while (unlikely(size > copied));
	264	return copied;
	265	}
	266	EXPORT_SYMBOL(tty_insert_flip_string);
	267
	268	/**
	269	* tty_insert_flip_string_flags - Add characters to the tty buffer
	270	* @tty: tty structure
	271	* @chars: characters
	272	* @flags: flag bytes
	273	* @size: size
	274	*
	275	* Queue a series of bytes to the tty buffering. For each character
	276	* the flags array indicates the status of the character. Returns the
	277	* number added.
	278	*
	279	* Locking: Called functions may take tty->buf.lock
	280	*/
	281
	282	int tty_insert_flip_string_flags(struct tty_struct *tty,
	283	const unsigned char chars, const char flags, size_t size)
	284	{
	285	int copied = 0;
	286	do {
d9661adf AC	287	int goal = min(size - copied, TTY_BUFFER_PAGE);
d9661adf AC	288	int space = tty_buffer_request_room(tty, goal);
e0495736 AC	289	struct tty_buffer *tb = tty->buf.tail;
	290	/* If there is no space then tb may be NULL */
	291	if (unlikely(space == 0))
	292	break;
	293	memcpy(tb->char_buf_ptr + tb->used, chars, space);
	294	memcpy(tb->flag_buf_ptr + tb->used, flags, space);
	295	tb->used += space;
	296	copied += space;
	297	chars += space;
	298	flags += space;
	299	/* There is a small chance that we need to split the data over
	300	several buffers. If this is the case we must loop */
	301	} while (unlikely(size > copied));
	302	return copied;
	303	}
	304	EXPORT_SYMBOL(tty_insert_flip_string_flags);
	305
	306	/**
	307	* tty_schedule_flip - push characters to ldisc
	308	* @tty: tty to push from
	309	*
	310	* Takes any pending buffers and transfers their ownership to the
	311	* ldisc side of the queue. It then schedules those characters for
	312	* processing by the line discipline.
	313	*
	314	* Locking: Takes tty->buf.lock
	315	*/
	316
	317	void tty_schedule_flip(struct tty_struct *tty)
	318	{
	319	unsigned long flags;
	320	spin_lock_irqsave(&tty->buf.lock, flags);
	321	if (tty->buf.tail != NULL)
	322	tty->buf.tail->commit = tty->buf.tail->used;
	323	spin_unlock_irqrestore(&tty->buf.lock, flags);
	324	schedule_delayed_work(&tty->buf.work, 1);
	325	}
	326	EXPORT_SYMBOL(tty_schedule_flip);
	327
	328	/**
	329	* tty_prepare_flip_string - make room for characters
	330	* @tty: tty
	331	* @chars: return pointer for character write area
	332	* @size: desired size
	333	*
	334	* Prepare a block of space in the buffer for data. Returns the length
	335	* available and buffer pointer to the space which is now allocated and
	336	* accounted for as ready for normal characters. This is used for drivers
	337	* that need their own block copy routines into the buffer. There is no
	338	* guarantee the buffer is a DMA target!
	339	*
	340	* Locking: May call functions taking tty->buf.lock
	341	*/
	342
	343	int tty_prepare_flip_string(struct tty_struct tty, unsigned char *chars,
	344	size_t size)
	345	{
	346	int space = tty_buffer_request_room(tty, size);
	347	if (likely(space)) {
	348	struct tty_buffer *tb = tty->buf.tail;
	349	*chars = tb->char_buf_ptr + tb->used;
	350	memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
	351	tb->used += space;
	352	}
353	return space;
354	}
355	EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
356
357	/**
358	* tty_prepare_flip_string_flags - make room for characters
359	* @tty: tty
360	* @chars: return pointer for character write area
361	* @flags: return pointer for status flag write area
362	* @size: desired size
363	*
364	* Prepare a block of space in the buffer for data. Returns the length
365	* available and buffer pointer to the space which is now allocated and
366	* accounted for as ready for characters. This is used for drivers
367	* that need their own block copy routines into the buffer. There is no
368	* guarantee the buffer is a DMA target!
369	*
370	* Locking: May call functions taking tty->buf.lock
371	*/
372
373	int tty_prepare_flip_string_flags(struct tty_struct *tty,
374	unsigned char chars, char flags, size_t size)
375	{
376	int space = tty_buffer_request_room(tty, size);
377	if (likely(space)) {
378	struct tty_buffer *tb = tty->buf.tail;
379	*chars = tb->char_buf_ptr + tb->used;
380	*flags = tb->flag_buf_ptr + tb->used;
381	tb->used += space;
382	}
383	return space;
384	}
385	EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
386
387
388
389	/**
390	* flush_to_ldisc
391	* @work: tty structure passed from work queue.
392	*
393	* This routine is called out of the software interrupt to flush data
394	* from the buffer chain to the line discipline.
395	*
396	* Locking: holds tty->buf.lock to guard buffer list. Drops the lock
397	* while invoking the line discipline receive_buf method. The
398	* receive_buf method is single threaded for each tty instance.
399	*/
400
401	static void flush_to_ldisc(struct work_struct *work)
402	{
403	struct tty_struct *tty =
404	container_of(work, struct tty_struct, buf.work.work);
405	unsigned long flags;
406	struct tty_ldisc *disc;
e0495736 AC	407
	408	disc = tty_ldisc_ref(tty);
	409	if (disc == NULL) /* !TTY_LDISC */
	410	return;
	411
	412	spin_lock_irqsave(&tty->buf.lock, flags);
45242006 LT	413
	414	if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {
	415	struct tty_buffer *head;
	416	while ((head = tty->buf.head) != NULL) {
	417	int count;
	418	char *char_buf;
	419	unsigned char *flag_buf;
	420
	421	count = head->commit - head->read;
e0495736 AC	422	if (!count) {
	423	if (head->next == NULL)
	424	break;
45242006 LT	425	tty->buf.head = head->next;
45242006 LT	426	tty_buffer_free(tty, head);
e0495736 AC	427	continue;
	428	}
	429	/* Ldisc or user is trying to flush the buffers
	430	we are feeding to the ldisc, stop feeding the
	431	line discipline as we want to empty the queue */
	432	if (test_bit(TTY_FLUSHPENDING, &tty->flags))
	433	break;
	434	if (!tty->receive_room) {
	435	schedule_delayed_work(&tty->buf.work, 1);
	436	break;
	437	}
	438	if (count > tty->receive_room)
	439	count = tty->receive_room;
	440	char_buf = head->char_buf_ptr + head->read;
	441	flag_buf = head->flag_buf_ptr + head->read;
	442	head->read += count;
	443	spin_unlock_irqrestore(&tty->buf.lock, flags);
	444	disc->ops->receive_buf(tty, char_buf,
	445	flag_buf, count);
	446	spin_lock_irqsave(&tty->buf.lock, flags);
	447	}
45242006	448	clear_bit(TTY_FLUSHING, &tty->flags);
e0495736	449	}
45242006	450
e0495736 AC	451	/* We may have a deferred request to flush the input buffer,
	452	if so pull the chain under the lock and empty the queue */
	453	if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
	454	__tty_buffer_flush(tty);
	455	clear_bit(TTY_FLUSHPENDING, &tty->flags);
	456	wake_up(&tty->read_wait);
	457	}
e0495736 AC	458	spin_unlock_irqrestore(&tty->buf.lock, flags);
	459
	460	tty_ldisc_deref(disc);
	461	}
	462
e043e42b OH	463	/**
	464	* tty_flush_to_ldisc
	465	* @tty: tty to push
	466	*
	467	* Push the terminal flip buffers to the line discipline.
	468	*
	469	* Must not be called from IRQ context.
	470	*/
	471	void tty_flush_to_ldisc(struct tty_struct *tty)
	472	{
514fc01d	473	flush_delayed_work(&tty->buf.work);
e043e42b OH	474	}
e043e42b OH	475
e0495736 AC	476	/**
	477	* tty_flip_buffer_push - terminal
	478	* @tty: tty to push
	479	*
	480	* Queue a push of the terminal flip buffers to the line discipline. This
	481	* function must not be called from IRQ context if tty->low_latency is set.
	482	*
	483	* In the event of the queue being busy for flipping the work will be
	484	* held off and retried later.
	485	*
	486	* Locking: tty buffer lock. Driver locks in low latency mode.
	487	*/
	488
	489	void tty_flip_buffer_push(struct tty_struct *tty)
	490	{
	491	unsigned long flags;
	492	spin_lock_irqsave(&tty->buf.lock, flags);
	493	if (tty->buf.tail != NULL)
	494	tty->buf.tail->commit = tty->buf.tail->used;
	495	spin_unlock_irqrestore(&tty->buf.lock, flags);
	496
	497	if (tty->low_latency)
	498	flush_to_ldisc(&tty->buf.work.work);
	499	else
	500	schedule_delayed_work(&tty->buf.work, 1);
	501	}
	502	EXPORT_SYMBOL(tty_flip_buffer_push);
	503
	504	/**
	505	* tty_buffer_init - prepare a tty buffer structure
	506	* @tty: tty to initialise
	507	*
	508	* Set up the initial state of the buffer management for a tty device.
	509	* Must be called before the other tty buffer functions are used.
	510	*
	511	* Locking: none
	512	*/
	513
	514	void tty_buffer_init(struct tty_struct *tty)
	515	{
	516	spin_lock_init(&tty->buf.lock);
	517	tty->buf.head = NULL;
	518	tty->buf.tail = NULL;
	519	tty->buf.free = NULL;
	520	tty->buf.memory_used = 0;
	521	INIT_DELAYED_WORK(&tty->buf.work, flush_to_ldisc);
	522	}
	523