tty_io.c

来自「linux 内核源代码」· C语言 代码 · 共 2,498 行 · 第 1/5 页

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 space = tty_buffer_request_room(tty, size - copied);
		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 space = tty_buffer_request_room(tty, size - copied);
		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);



/**
 *	tty_set_termios_ldisc		-	set ldisc field
 *	@tty: tty structure
 *	@num: line discipline number
 *
 *	This is probably overkill for real world processors but
 *	they are not on hot paths so a little discipline won't do 
 *	any harm.
 *
 *	Locking: takes termios_mutex
 */
 
static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
{
	mutex_lock(&tty->termios_mutex);
	tty->termios->c_line = num;
	mutex_unlock(&tty->termios_mutex);
}

/*
 *	This guards the refcounted line discipline lists. The lock
 *	must be taken with irqs off because there are hangup path
 *	callers who will do ldisc lookups and cannot sleep.
 */
 
static DEFINE_SPINLOCK(tty_ldisc_lock);
static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
static struct tty_ldisc tty_ldiscs[NR_LDISCS];	/* line disc dispatch table */

/**
 *	tty_register_ldisc	-	install a line discipline
 *	@disc: ldisc number
 *	@new_ldisc: pointer to the ldisc object
 *
 *	Installs a new line discipline into the kernel. The discipline
 *	is set up as unreferenced and then made available to the kernel
 *	from this point onwards.
 *
 *	Locking:
 *		takes tty_ldisc_lock to guard against ldisc races
 */

int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
{
	unsigned long flags;
	int ret = 0;
	
	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;
	
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	tty_ldiscs[disc] = *new_ldisc;
	tty_ldiscs[disc].num = disc;
	tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
	tty_ldiscs[disc].refcount = 0;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	
	return ret;
}
EXPORT_SYMBOL(tty_register_ldisc);

/**
 *	tty_unregister_ldisc	-	unload a line discipline
 *	@disc: ldisc number
 *	@new_ldisc: pointer to the ldisc object
 *
 *	Remove a line discipline from the kernel providing it is not
 *	currently in use.
 *
 *	Locking:
 *		takes tty_ldisc_lock to guard against ldisc races
 */

int tty_unregister_ldisc(int disc)
{
	unsigned long flags;
	int ret = 0;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if (tty_ldiscs[disc].refcount)
		ret = -EBUSY;
	else
		tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	return ret;
}
EXPORT_SYMBOL(tty_unregister_ldisc);

/**
 *	tty_ldisc_get		-	take a reference to an ldisc
 *	@disc: ldisc number
 *
 *	Takes a reference to a line discipline. Deals with refcounts and
 *	module locking counts. Returns NULL if the discipline is not available.
 *	Returns a pointer to the discipline and bumps the ref count if it is
 *	available
 *
 *	Locking:
 *		takes tty_ldisc_lock to guard against ldisc races
 */

struct tty_ldisc *tty_ldisc_get(int disc)
{
	unsigned long flags;
	struct tty_ldisc *ld;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return NULL;
	
	spin_lock_irqsave(&tty_ldisc_lock, flags);

	ld = &tty_ldiscs[disc];
	/* Check the entry is defined */
	if(ld->flags & LDISC_FLAG_DEFINED)
	{
		/* If the module is being unloaded we can't use it */
		if (!try_module_get(ld->owner))
		       	ld = NULL;
		else /* lock it */
			ld->refcount++;
	}
	else
		ld = NULL;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	return ld;
}

EXPORT_SYMBOL_GPL(tty_ldisc_get);

/**
 *	tty_ldisc_put		-	drop ldisc reference
 *	@disc: ldisc number
 *
 *	Drop a reference to a line discipline. Manage refcounts and
 *	module usage counts
 *
 *	Locking:
 *		takes tty_ldisc_lock to guard against ldisc races
 */

void tty_ldisc_put(int disc)
{
	struct tty_ldisc *ld;
	unsigned long flags;
	
	BUG_ON(disc < N_TTY || disc >= NR_LDISCS);
		
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	ld = &tty_ldiscs[disc];
	BUG_ON(ld->refcount == 0);
	ld->refcount--;
	module_put(ld->owner);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
}
	
EXPORT_SYMBOL_GPL(tty_ldisc_put);

/**
 *	tty_ldisc_assign	-	set ldisc on a tty
 *	@tty: tty to assign
 *	@ld: line discipline
 *
 *	Install an instance of a line discipline into a tty structure. The
 *	ldisc must have a reference count above zero to ensure it remains/
 *	The tty instance refcount starts at zero.
 *
 *	Locking:
 *		Caller must hold references
 */

static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
{
	tty->ldisc = *ld;
	tty->ldisc.refcount = 0;
}

/**
 *	tty_ldisc_try		-	internal helper
 *	@tty: the tty
 *
 *	Make a single attempt to grab and bump the refcount on
 *	the tty ldisc. Return 0 on failure or 1 on success. This is
 *	used to implement both the waiting and non waiting versions
 *	of tty_ldisc_ref
 *
 *	Locking: takes tty_ldisc_lock
 */

static int tty_ldisc_try(struct tty_struct *tty)
{
	unsigned long flags;
	struct tty_ldisc *ld;
	int ret = 0;
	
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	ld = &tty->ldisc;
	if(test_bit(TTY_LDISC, &tty->flags))
	{
		ld->refcount++;
		ret = 1;
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	return ret;
}

/**
 *	tty_ldisc_ref_wait	-	wait for the tty ldisc
 *	@tty: tty device
 *
 *	Dereference the line discipline for the terminal and take a 
 *	reference to it. If the line discipline is in flux then 
 *	wait patiently until it changes.
 *
 *	Note: Must not be called from an IRQ/timer context. The caller
 *	must also be careful not to hold other locks that will deadlock
 *	against a discipline change, such as an existing ldisc reference
 *	(which we check for)
 *
 *	Locking: call functions take tty_ldisc_lock
 */
 
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
{
	/* wait_event is a macro */
	wait_event(tty_ldisc_wait, tty_ldisc_try(tty));
	if(tty->ldisc.refcount == 0)
		printk(KERN_ERR "tty_ldisc_ref_wait\n");
	return &tty->ldisc;
}

EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);

/**
 *	tty_ldisc_ref		-	get the tty ldisc
 *	@tty: tty device
 *
 *	Dereference the line discipline for the terminal and take a 
 *	reference to it. If the line discipline is in flux then 
 *	return NULL. Can be called from IRQ and timer functions.
 *
 *	Locking: called functions take tty_ldisc_lock
 */
 
struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
{
	if(tty_ldisc_try(tty))
		return &tty->ldisc;
	return NULL;
}

EXPORT_SYMBOL_GPL(tty_ldisc_ref);

/**
 *	tty_ldisc_deref		-	free a tty ldisc reference
 *	@ld: reference to free up
 *
 *	Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
 *	be called in IRQ context.
 *
 *	Locking: takes tty_ldisc_lock
 */
 
void tty_ldisc_deref(struct tty_ldisc *ld)
{
	unsigned long flags;

	BUG_ON(ld == NULL);
		
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if(ld->refcount == 0)
		printk(KERN_ERR "tty_ldisc_deref: no references.\n");
	else
		ld->refcount--;
	if(ld->refcount == 0)
		wake_up(&tty_ldisc_wait);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
}

EXPORT_SYMBOL_GPL(tty_ldisc_deref);

/**
 *	tty_ldisc_enable	-	allow ldisc use
 *	@tty: terminal to activate ldisc on
 *
 *	Set the TTY_LDISC flag when the line discipline can be called
 *	again. Do necessary wakeups for existing sleepers.
 *
 *	Note: nobody should set this bit except via this function. Clearing
 *	directly is allowed.
 */

static void tty_ldisc_enable(struct tty_struct *tty)
{
	set_bit(TTY_LDISC, &tty->flags);
	wake_up(&tty_ldisc_wait);
}
	
/**
 *	tty_set_ldisc		-	set line discipline
 *	@tty: the terminal to set
 *	@ldisc: the line discipline
 *
 *	Set the discipline of a tty line. Must be called from a process
 *	context.
 *
 *	Locking: takes tty_ldisc_lock.
 *		 called functions take termios_mutex
 */
 
static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
	int retval = 0;
	struct tty_ldisc o_ldisc;
	char buf[64];
	int work;
	unsigned long flags;
	struct tty_ldisc *ld;
	struct tty_struct *o_tty;

	if ((ldisc < N_TTY) || (ldisc >= NR_LDISCS))
		return -EINVAL;

restart:

	ld = tty_ldisc_get(ldisc);
	/* Eduardo Blanco <[e-mail]> */
	/* Cyrus Durgin <[e-mail]> */
	if (ld == NULL) {
		request_module("tty-ldisc-%d", ldisc);
		ld = tty_ldisc_get(ldisc);
	}
	if (ld == NULL)
		return -EINVAL;

	/*
	 *	Problem: What do we do if this blocks ?
	 */

	tty_wait_until_sent(tty, 0);