first commit

1 files changed, 548 insertions, 0 deletions

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
new file mode 100644
index 000000000..a42a028a9
--- /dev/null
+++ b/drivers/tty/tty_buffer.c
@@ -0,0 +1,548 @@
+/*
+ * 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>
+#include <linux/ratelimit.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_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+	struct tty_buffer *thead;
+
+	while ((thead = buf->head) != NULL) {
+		buf->head = thead->next;
+		kfree(thead);
+	}
+	while ((thead = buf->free) != NULL) {
+		buf->free = thead->next;
+		kfree(thead);
+	}
+	buf->tail = NULL;
+	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_port *port, size_t size)
+{
+	struct tty_buffer *p;
+
+	if (port->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;
+	port->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_port *port, struct tty_buffer *b)
+{
+	struct tty_bufhead *buf = &port->buf;
+
+	/* Dumb strategy for now - should keep some stats */
+	buf->memory_used -= b->size;
+	WARN_ON(buf->memory_used < 0);
+
+	if (b->size >= 512)
+		kfree(b);
+	else {
+		b->next = buf->free;
+		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_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+	struct tty_buffer *thead;
+
+	if (unlikely(buf->head == NULL))
+		return;
+	while ((thead = buf->head->next) != NULL) {
+		tty_buffer_free(port, buf->head);
+		buf->head = thead;
+	}
+	WARN_ON(buf->head != buf->tail);
+	buf->head->read = buf->head->commit;
+}
+
+/**
+ *	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)
+{
+	struct tty_port *port = tty->port;
+	struct tty_bufhead *buf = &port->buf;
+	unsigned long flags;
+
+	spin_lock_irqsave(&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(TTYP_FLUSHING, &port->iflags)) {
+		set_bit(TTYP_FLUSHPENDING, &port->iflags);
+		spin_unlock_irqrestore(&buf->lock, flags);
+		wait_event(tty->read_wait,
+				test_bit(TTYP_FLUSHPENDING, &port->iflags) == 0);
+		return;
+	} else
+		__tty_buffer_flush(port);
+	spin_unlock_irqrestore(&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_port *port, size_t size)
+{
+	struct tty_buffer **tbh = &port->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;
+			port->buf.memory_used += t->size;
+			return t;
+		}
+		tbh = &((*tbh)->next);
+	}
+	/* Round the buffer size out */
+	size = (size + 0xFF) & ~0xFF;
+	return tty_buffer_alloc(port, 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 port->buf.lock
+ */
+int tty_buffer_request_room(struct tty_port *port, size_t size)
+{
+	struct tty_bufhead *buf = &port->buf;
+	struct tty_buffer *b, *n;
+	int left;
+	unsigned long flags;
+	spin_lock_irqsave(&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 */
+	b = buf->tail;
+	if (b != 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(port, size)) != NULL) {
+			if (b != NULL) {
+				b->next = n;
+				b->commit = b->used;
+			} else
+				buf->head = n;
+			buf->tail = n;
+		} else
+			size = left;
+	}
+	spin_unlock_irqrestore(&buf->lock, flags);
+	return size;
+}
+EXPORT_SYMBOL_GPL(tty_buffer_request_room);
+
+/**
+ *	tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
+ *	@port: tty port
+ *	@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 port->buf.lock
+ */
+
+int tty_insert_flip_string_fixed_flag(struct tty_port *port,
+		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 = tty_buffer_request_room(port, goal);
+		struct tty_buffer *tb = port->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, flag, 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_fixed_flag);
+
+/**
+ *	tty_insert_flip_string_flags	-	Add characters to the tty buffer
+ *	@port: tty port
+ *	@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 port->buf.lock
+ */
+
+int tty_insert_flip_string_flags(struct tty_port *port,
+		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 = tty_buffer_request_room(port, goal);
+		struct tty_buffer *tb = port->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
+ *	@port: tty port 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.
+ *	Note that this function can only be used when the low_latency flag
+ *	is unset. Otherwise the workqueue won't be flushed.
+ *
+ *	Locking: Takes port->buf.lock
+ */
+
+void tty_schedule_flip(struct tty_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+	unsigned long flags;
+	WARN_ON(port->low_latency);
+
+	spin_lock_irqsave(&buf->lock, flags);
+	if (buf->tail != NULL)
+		buf->tail->commit = buf->tail->used;
+	spin_unlock_irqrestore(&buf->lock, flags);
+	schedule_work(&buf->work);
+}
+EXPORT_SYMBOL(tty_schedule_flip);
+
+/**
+ *	tty_prepare_flip_string		-	make room for characters
+ *	@port: tty port
+ *	@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 port->buf.lock
+ */
+
+int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
+		size_t size)
+{
+	int space = tty_buffer_request_room(port, size);
+	if (likely(space)) {
+		struct tty_buffer *tb = port->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
+ *	@port: tty port
+ *	@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 port->buf.lock
+ */
+
+int tty_prepare_flip_string_flags(struct tty_port *port,
+			unsigned char **chars, char **flags, size_t size)
+{
+	int space = tty_buffer_request_room(port, size);
+	if (likely(space)) {
+		struct tty_buffer *tb = port->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_port *port = container_of(work, struct tty_port, buf.work);
+	struct tty_bufhead *buf = &port->buf;
+	struct tty_struct *tty;
+	unsigned long 	flags;
+	struct tty_ldisc *disc;
+
+	tty = port->itty;
+	if (tty == NULL)
+		return;
+
+	disc = tty_ldisc_ref(tty);
+	if (disc == NULL)
+		return;
+
+	spin_lock_irqsave(&buf->lock, flags);
+
+	if (!test_and_set_bit(TTYP_FLUSHING, &port->iflags)) {
+		struct tty_buffer *head;
+		while ((head = buf->head) != NULL) {
+			int count;
+			char *char_buf;
+			unsigned char *flag_buf;
+
+			count = head->commit - head->read;
+			if (!count) {
+				if (head->next == NULL)
+					break;
+				buf->head = head->next;
+				tty_buffer_free(port, head);
+				continue;
+			}
+			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(&buf->lock, flags);
+			disc->ops->receive_buf(tty, char_buf,
+							flag_buf, count);
+			spin_lock_irqsave(&buf->lock, flags);
+			/* Ldisc or user is trying to flush the buffers.
+			   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(TTYP_FLUSHPENDING, &port->iflags)) {
+				__tty_buffer_flush(port);
+				clear_bit(TTYP_FLUSHPENDING, &port->iflags);
+				wake_up(&tty->read_wait);
+				break;
+			}
+		}
+		clear_bit(TTYP_FLUSHING, &port->iflags);
+	}
+
+	spin_unlock_irqrestore(&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)
+{
+	if (!tty->port->low_latency)
+		flush_work(&tty->port->buf.work);
+}
+
+/**
+ *	tty_flip_buffer_push	-	terminal
+ *	@port: tty port to push
+ *
+ *	Queue a push of the terminal flip buffers to the line discipline. This
+ *	function must not be called from IRQ context if port->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_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+	unsigned long flags;
+
+	spin_lock_irqsave(&buf->lock, flags);
+	if (buf->tail != NULL)
+		buf->tail->commit = buf->tail->used;
+	spin_unlock_irqrestore(&buf->lock, flags);
+
+	if (port->low_latency)
+		flush_to_ldisc(&buf->work);
+	else
+		schedule_work(&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_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+
+	spin_lock_init(&buf->lock);
+	buf->head = NULL;
+	buf->tail = NULL;
+	buf->free = NULL;
+	buf->memory_used = 0;
+	INIT_WORK(&buf->work, flush_to_ldisc);
+}
+