[deliverable/linux.git] / drivers / tty / 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: Caller must hold tty->buf.lock
 */
static int __tty_buffer_request_room(struct tty_struct *tty, size_t size)
{
	struct tty_buffer *b, *n;
	int left;
	/* 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;
	}

	return size;
}


/**
 *	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)
{
	unsigned long flags;
	int length;

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

/**
 *	tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
 *	@tty: tty structure
 *	@chars: characters
 *	@flag: flag value for each character
 *	@size: size
 *
 *	Queue a series of bytes to the tty buffering. All the characters
 *	passed are marked with the supplied flag. Returns the number added.
 *
 *	Locking: Called functions may take tty->buf.lock
 */

int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
		const unsigned char *chars, char flag, size_t size)
{
	int copied = 0;
	do {
		int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
		int space;
		unsigned long flags;
		struct tty_buffer *tb;

		spin_lock_irqsave(&tty->buf.lock, flags);
		space = __tty_buffer_request_room(tty, goal);
		tb = tty->buf.tail;
		/* If there is no space then tb may be NULL */
		if (unlikely(space == 0)) {
			spin_unlock_irqrestore(&tty->buf.lock, flags);
			break;
		}
		memcpy(tb->char_buf_ptr + tb->used, chars, space);
		memset(tb->flag_buf_ptr + tb->used, flag, space);
		tb->used += space;
		spin_unlock_irqrestore(&tty->buf.lock, flags);
		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_fixed_flag);

/**
 *	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_t(size_t, size - copied, TTY_BUFFER_PAGE);
		int space;
		unsigned long __flags;
		struct tty_buffer *tb;

		spin_lock_irqsave(&tty->buf.lock, __flags);
		space = __tty_buffer_request_room(tty, goal);
		tb = tty->buf.tail;
		/* If there is no space then tb may be NULL */
		if (unlikely(space == 0)) {
			spin_unlock_irqrestore(&tty->buf.lock, __flags);
			break;
		}
		memcpy(tb->char_buf_ptr + tb->used, chars, space);
		memcpy(tb->flag_buf_ptr + tb->used, flags, space);
		tb->used += space;
		spin_unlock_irqrestore(&tty->buf.lock, __flags);
		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_work(&tty->buf.work);
}
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;
	unsigned long flags;
	struct tty_buffer *tb;

	spin_lock_irqsave(&tty->buf.lock, flags);
	space = __tty_buffer_request_room(tty, size);

	tb = tty->buf.tail;
	if (likely(space)) {
		*chars = tb->char_buf_ptr + tb->used;
		memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
		tb->used += space;
	}
	spin_unlock_irqrestore(&tty->buf.lock, flags);
	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;
	unsigned long __flags;
	struct tty_buffer *tb;

	spin_lock_irqsave(&tty->buf.lock, __flags);
	space = __tty_buffer_request_room(tty, size);

	tb = tty->buf.tail;
	if (likely(space)) {
		*chars = tb->char_buf_ptr + tb->used;
		*flags = tb->flag_buf_ptr + tb->used;
		tb->used += space;
	}
	spin_unlock_irqrestore(&tty->buf.lock, __flags);
	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);
	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)
				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_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);
	else
		schedule_work(&tty->buf.work);
}
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_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	}
e0495736	188	/**
c56a00a1	189	* __tty_buffer_request_room - grow tty buffer if needed
e0495736 AC	190	* @tty: tty structure
	191	* @size: size desired
	192	*
	193	* Make at least size bytes of linear space available for the tty
	194	* buffer. If we fail return the size we managed to find.
c56a00a1	195	* Locking: Caller must hold tty->buf.lock
e0495736	196	*/
c56a00a1	197	static int __tty_buffer_request_room(struct tty_struct *tty, size_t size)
e0495736 AC	198	{
	199	struct tty_buffer b, n;
	200	int left;
e0495736 AC	201	/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
	202	remove this conditional if its worth it. This would be invisible
	203	to the callers */
	204	if ((b = tty->buf.tail) != NULL)
	205	left = b->size - b->used;
	206	else
	207	left = 0;
	208
	209	if (left < size) {
	210	/* This is the slow path - looking for new buffers to use */
	211	if ((n = tty_buffer_find(tty, size)) != NULL) {
	212	if (b != NULL) {
	213	b->next = n;
	214	b->commit = b->used;
	215	} else
	216	tty->buf.head = n;
	217	tty->buf.tail = n;
	218	} else
	219	size = left;
	220	}
	221
e0495736 AC	222	return size;
e0495736 AC	223	}
c56a00a1 XT	224
	225
	226	/**
	227	* tty_buffer_request_room - grow tty buffer if needed
	228	* @tty: tty structure
	229	* @size: size desired
	230	*
	231	* Make at least size bytes of linear space available for the tty
	232	* buffer. If we fail return the size we managed to find.
	233	*
	234	* Locking: Takes tty->buf.lock
	235	*/
	236	int tty_buffer_request_room(struct tty_struct *tty, size_t size)
	237	{
	238	unsigned long flags;
	239	int length;
	240
	241	spin_lock_irqsave(&tty->buf.lock, flags);
	242	length = __tty_buffer_request_room(tty, size);
	243	spin_unlock_irqrestore(&tty->buf.lock, flags);
	244	return length;
	245	}
e0495736 AC	246	EXPORT_SYMBOL_GPL(tty_buffer_request_room);
	247
	248	/**
2832fc11	249	* tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
e0495736 AC	250	* @tty: tty structure
e0495736 AC	251	* @chars: characters
2832fc11	252	* @flag: flag value for each character
e0495736 AC	253	* @size: size
	254	*
	255	* Queue a series of bytes to the tty buffering. All the characters
ccc5ca8d	256	* passed are marked with the supplied flag. Returns the number added.
e0495736 AC	257	*
	258	* Locking: Called functions may take tty->buf.lock
	259	*/
	260
2832fc11 AC	261	int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
2832fc11 AC	262	const unsigned char *chars, char flag, size_t size)
e0495736 AC	263	{
	264	int copied = 0;
	265	do {
d4bee0a6	266	int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
c56a00a1 XT	267	int space;
	268	unsigned long flags;
	269	struct tty_buffer *tb;
	270
	271	spin_lock_irqsave(&tty->buf.lock, flags);
	272	space = __tty_buffer_request_room(tty, goal);
	273	tb = tty->buf.tail;
e0495736	274	/* If there is no space then tb may be NULL */
c56a00a1 XT	275	if (unlikely(space == 0)) {
c56a00a1 XT	276	spin_unlock_irqrestore(&tty->buf.lock, flags);
e0495736	277	break;
c56a00a1	278	}
e0495736	279	memcpy(tb->char_buf_ptr + tb->used, chars, space);
2832fc11	280	memset(tb->flag_buf_ptr + tb->used, flag, space);
e0495736	281	tb->used += space;
c56a00a1	282	spin_unlock_irqrestore(&tty->buf.lock, flags);
e0495736 AC	283	copied += space;
	284	chars += space;
	285	/* There is a small chance that we need to split the data over
	286	several buffers. If this is the case we must loop */
	287	} while (unlikely(size > copied));
	288	return copied;
	289	}
2832fc11	290	EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
e0495736 AC	291
	292	/**
	293	* tty_insert_flip_string_flags - Add characters to the tty buffer
	294	* @tty: tty structure
	295	* @chars: characters
	296	* @flags: flag bytes
	297	* @size: size
	298	*
	299	* Queue a series of bytes to the tty buffering. For each character
	300	* the flags array indicates the status of the character. Returns the
	301	* number added.
	302	*
	303	* Locking: Called functions may take tty->buf.lock
	304	*/
	305
	306	int tty_insert_flip_string_flags(struct tty_struct *tty,
	307	const unsigned char chars, const char flags, size_t size)
	308	{
	309	int copied = 0;
	310	do {
d4bee0a6	311	int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
c56a00a1 XT	312	int space;
	313	unsigned long __flags;
	314	struct tty_buffer *tb;
	315
	316	spin_lock_irqsave(&tty->buf.lock, __flags);
	317	space = __tty_buffer_request_room(tty, goal);
	318	tb = tty->buf.tail;
e0495736	319	/* If there is no space then tb may be NULL */
c56a00a1 XT	320	if (unlikely(space == 0)) {
c56a00a1 XT	321	spin_unlock_irqrestore(&tty->buf.lock, __flags);
e0495736	322	break;
c56a00a1	323	}
e0495736 AC	324	memcpy(tb->char_buf_ptr + tb->used, chars, space);
	325	memcpy(tb->flag_buf_ptr + tb->used, flags, space);
	326	tb->used += space;
c56a00a1	327	spin_unlock_irqrestore(&tty->buf.lock, __flags);
e0495736 AC	328	copied += space;
	329	chars += space;
	330	flags += space;
	331	/* There is a small chance that we need to split the data over
	332	several buffers. If this is the case we must loop */
	333	} while (unlikely(size > copied));
	334	return copied;
	335	}
	336	EXPORT_SYMBOL(tty_insert_flip_string_flags);
	337
	338	/**
	339	* tty_schedule_flip - push characters to ldisc
	340	* @tty: tty to push from
	341	*
	342	* Takes any pending buffers and transfers their ownership to the
	343	* ldisc side of the queue. It then schedules those characters for
	344	* processing by the line discipline.
	345	*
	346	* Locking: Takes tty->buf.lock
	347	*/
	348
	349	void tty_schedule_flip(struct tty_struct *tty)
	350	{
	351	unsigned long flags;
	352	spin_lock_irqsave(&tty->buf.lock, flags);
	353	if (tty->buf.tail != NULL)
	354	tty->buf.tail->commit = tty->buf.tail->used;
	355	spin_unlock_irqrestore(&tty->buf.lock, flags);
f23eb2b2	356	schedule_work(&tty->buf.work);
e0495736 AC	357	}
	358	EXPORT_SYMBOL(tty_schedule_flip);
	359
	360	/**
	361	* tty_prepare_flip_string - make room for characters
	362	* @tty: tty
	363	* @chars: return pointer for character write area
	364	* @size: desired size
	365	*
	366	* Prepare a block of space in the buffer for data. Returns the length
	367	* available and buffer pointer to the space which is now allocated and
	368	* accounted for as ready for normal characters. This is used for drivers
	369	* that need their own block copy routines into the buffer. There is no
	370	* guarantee the buffer is a DMA target!
	371	*
	372	* Locking: May call functions taking tty->buf.lock
	373	*/
	374
	375	int tty_prepare_flip_string(struct tty_struct tty, unsigned char *chars,
	376	size_t size)
	377	{
c56a00a1 XT	378	int space;
	379	unsigned long flags;
	380	struct tty_buffer *tb;
	381
	382	spin_lock_irqsave(&tty->buf.lock, flags);
	383	space = __tty_buffer_request_room(tty, size);
	384
	385	tb = tty->buf.tail;
e0495736	386	if (likely(space)) {
e0495736 AC	387	*chars = tb->char_buf_ptr + tb->used;
	388	memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
	389	tb->used += space;
	390	}
c56a00a1	391	spin_unlock_irqrestore(&tty->buf.lock, flags);
e0495736 AC	392	return space;
	393	}
	394	EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
	395
	396	/**
	397	* tty_prepare_flip_string_flags - make room for characters
	398	* @tty: tty
	399	* @chars: return pointer for character write area
	400	* @flags: return pointer for status flag write area
	401	* @size: desired size
	402	*
	403	* Prepare a block of space in the buffer for data. Returns the length
	404	* available and buffer pointer to the space which is now allocated and
	405	* accounted for as ready for characters. This is used for drivers
	406	* that need their own block copy routines into the buffer. There is no
	407	* guarantee the buffer is a DMA target!
	408	*
	409	* Locking: May call functions taking tty->buf.lock
	410	*/
	411
	412	int tty_prepare_flip_string_flags(struct tty_struct *tty,
	413	unsigned char chars, char flags, size_t size)
	414	{
c56a00a1 XT	415	int space;
	416	unsigned long __flags;
	417	struct tty_buffer *tb;
	418
	419	spin_lock_irqsave(&tty->buf.lock, __flags);
	420	space = __tty_buffer_request_room(tty, size);
	421
	422	tb = tty->buf.tail;
e0495736	423	if (likely(space)) {
e0495736 AC	424	*chars = tb->char_buf_ptr + tb->used;
	425	*flags = tb->flag_buf_ptr + tb->used;
	426	tb->used += space;
	427	}
c56a00a1	428	spin_unlock_irqrestore(&tty->buf.lock, __flags);
e0495736 AC	429	return space;
	430	}
	431	EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
	432
	433
	434
	435	/**
	436	* flush_to_ldisc
	437	* @work: tty structure passed from work queue.
	438	*
	439	* This routine is called out of the software interrupt to flush data
	440	* from the buffer chain to the line discipline.
	441	*
	442	* Locking: holds tty->buf.lock to guard buffer list. Drops the lock
	443	* while invoking the line discipline receive_buf method. The
	444	* receive_buf method is single threaded for each tty instance.
	445	*/
	446
	447	static void flush_to_ldisc(struct work_struct *work)
	448	{
	449	struct tty_struct *tty =
f23eb2b2	450	container_of(work, struct tty_struct, buf.work);
e0495736 AC	451	unsigned long flags;
e0495736 AC	452	struct tty_ldisc *disc;
e0495736 AC	453
	454	disc = tty_ldisc_ref(tty);
	455	if (disc == NULL) /* !TTY_LDISC */
	456	return;
	457
	458	spin_lock_irqsave(&tty->buf.lock, flags);
45242006 LT	459
45242006 LT	460	if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {
81de916f	461	struct tty_buffer *head;
45242006 LT	462	while ((head = tty->buf.head) != NULL) {
	463	int count;
	464	char *char_buf;
	465	unsigned char *flag_buf;
	466
	467	count = head->commit - head->read;
e0495736 AC	468	if (!count) {
	469	if (head->next == NULL)
	470	break;
45242006 LT	471	tty->buf.head = head->next;
45242006 LT	472	tty_buffer_free(tty, head);
e0495736 AC	473	continue;
	474	}
	475	/* Ldisc or user is trying to flush the buffers
	476	we are feeding to the ldisc, stop feeding the
	477	line discipline as we want to empty the queue */
	478	if (test_bit(TTY_FLUSHPENDING, &tty->flags))
	479	break;
81de916f	480	if (!tty->receive_room)
55db4c64 LT	481	break;
	482	if (count > tty->receive_room)
	483	count = tty->receive_room;
e0495736 AC	484	char_buf = head->char_buf_ptr + head->read;
e0495736 AC	485	flag_buf = head->flag_buf_ptr + head->read;
55db4c64	486	head->read += count;
e0495736	487	spin_unlock_irqrestore(&tty->buf.lock, flags);
55db4c64	488	disc->ops->receive_buf(tty, char_buf,
e0495736 AC	489	flag_buf, count);
	490	spin_lock_irqsave(&tty->buf.lock, flags);
	491	}
45242006	492	clear_bit(TTY_FLUSHING, &tty->flags);
e0495736	493	}
45242006	494
e0495736 AC	495	/* We may have a deferred request to flush the input buffer,
	496	if so pull the chain under the lock and empty the queue */
	497	if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
	498	__tty_buffer_flush(tty);
	499	clear_bit(TTY_FLUSHPENDING, &tty->flags);
	500	wake_up(&tty->read_wait);
	501	}
e0495736 AC	502	spin_unlock_irqrestore(&tty->buf.lock, flags);
	503
	504	tty_ldisc_deref(disc);
	505	}
	506
e043e42b OH	507	/**
	508	* tty_flush_to_ldisc
	509	* @tty: tty to push
	510	*
	511	* Push the terminal flip buffers to the line discipline.
	512	*
	513	* Must not be called from IRQ context.
	514	*/
	515	void tty_flush_to_ldisc(struct tty_struct *tty)
	516	{
f23eb2b2	517	flush_work(&tty->buf.work);
e043e42b OH	518	}
e043e42b OH	519
e0495736 AC	520	/**
	521	* tty_flip_buffer_push - terminal
	522	* @tty: tty to push
	523	*
	524	* Queue a push of the terminal flip buffers to the line discipline. This
	525	* function must not be called from IRQ context if tty->low_latency is set.
	526	*
	527	* In the event of the queue being busy for flipping the work will be
	528	* held off and retried later.
	529	*
	530	* Locking: tty buffer lock. Driver locks in low latency mode.
	531	*/
	532
	533	void tty_flip_buffer_push(struct tty_struct *tty)
	534	{
	535	unsigned long flags;
	536	spin_lock_irqsave(&tty->buf.lock, flags);
	537	if (tty->buf.tail != NULL)
	538	tty->buf.tail->commit = tty->buf.tail->used;
	539	spin_unlock_irqrestore(&tty->buf.lock, flags);
	540
	541	if (tty->low_latency)
f23eb2b2	542	flush_to_ldisc(&tty->buf.work);
e0495736	543	else
f23eb2b2	544	schedule_work(&tty->buf.work);
e0495736 AC	545	}
	546	EXPORT_SYMBOL(tty_flip_buffer_push);
	547
	548	/**
	549	* tty_buffer_init - prepare a tty buffer structure
	550	* @tty: tty to initialise
	551	*
	552	* Set up the initial state of the buffer management for a tty device.
	553	* Must be called before the other tty buffer functions are used.
	554	*
	555	* Locking: none
	556	*/
	557
	558	void tty_buffer_init(struct tty_struct *tty)
	559	{
	560	spin_lock_init(&tty->buf.lock);
	561	tty->buf.head = NULL;
	562	tty->buf.tail = NULL;
	563	tty->buf.free = NULL;
	564	tty->buf.memory_used = 0;
f23eb2b2	565	INIT_WORK(&tty->buf.work, flush_to_ldisc);
e0495736 AC	566	}
e0495736 AC	567