hvc_console.c

来自「linux 内核源代码」· C语言 代码 · 共 908 行 · 第 1/2 页

	spin_unlock_irqrestore(&hp->lock, flags);
	if (irq)
		free_irq(irq, hp);
	while(temp_open_count) {
		--temp_open_count;
		kobject_put(kobjp);
	}
}

/*
 * Push buffered characters whether they were just recently buffered or waiting
 * on a blocked hypervisor.  Call this function with hp->lock held.
 */
static void hvc_push(struct hvc_struct *hp)
{
	int n;

	n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
	if (n <= 0) {
		if (n == 0) {
			hp->do_wakeup = 1;
			return;
		}
		/* throw away output on error; this happens when
		   there is no session connected to the vterm. */
		hp->n_outbuf = 0;
	} else
		hp->n_outbuf -= n;
	if (hp->n_outbuf > 0)
		memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
	else
		hp->do_wakeup = 1;
}

static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
{
	struct hvc_struct *hp = tty->driver_data;
	unsigned long flags;
	int rsize, written = 0;

	/* This write was probably executed during a tty close. */
	if (!hp)
		return -EPIPE;

	if (hp->count <= 0)
		return -EIO;

	spin_lock_irqsave(&hp->lock, flags);

	/* Push pending writes */
	if (hp->n_outbuf > 0)
		hvc_push(hp);

	while (count > 0 && (rsize = hp->outbuf_size - hp->n_outbuf) > 0) {
		if (rsize > count)
			rsize = count;
		memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
		count -= rsize;
		buf += rsize;
		hp->n_outbuf += rsize;
		written += rsize;
		hvc_push(hp);
	}
	spin_unlock_irqrestore(&hp->lock, flags);

	/*
	 * Racy, but harmless, kick thread if there is still pending data.
	 */
	if (hp->n_outbuf)
		hvc_kick();

	return written;
}

/*
 * This is actually a contract between the driver and the tty layer outlining
 * how much write room the driver can guarantee will be sent OR BUFFERED.  This
 * driver MUST honor the return value.
 */
static int hvc_write_room(struct tty_struct *tty)
{
	struct hvc_struct *hp = tty->driver_data;

	if (!hp)
		return -1;

	return hp->outbuf_size - hp->n_outbuf;
}

static int hvc_chars_in_buffer(struct tty_struct *tty)
{
	struct hvc_struct *hp = tty->driver_data;

	if (!hp)
		return -1;
	return hp->n_outbuf;
}

/*
 * timeout will vary between the MIN and MAX values defined here.  By default
 * and during console activity we will use a default MIN_TIMEOUT of 10.  When
 * the console is idle, we increase the timeout value on each pass through
 * msleep until we reach the max.  This may be noticeable as a brief (average
 * one second) delay on the console before the console responds to input when
 * there has been no input for some time.
 */
#define MIN_TIMEOUT		(10)
#define MAX_TIMEOUT		(2000)
static u32 timeout = MIN_TIMEOUT;

#define HVC_POLL_READ	0x00000001
#define HVC_POLL_WRITE	0x00000002

static int hvc_poll(struct hvc_struct *hp)
{
	struct tty_struct *tty;
	int i, n, poll_mask = 0;
	char buf[N_INBUF] __ALIGNED__;
	unsigned long flags;
	int read_total = 0;

	spin_lock_irqsave(&hp->lock, flags);

	/* Push pending writes */
	if (hp->n_outbuf > 0)
		hvc_push(hp);

	/* Reschedule us if still some write pending */
	if (hp->n_outbuf > 0)
		poll_mask |= HVC_POLL_WRITE;

	/* No tty attached, just skip */
	tty = hp->tty;
	if (tty == NULL)
		goto bail;

	/* Now check if we can get data (are we throttled ?) */
	if (test_bit(TTY_THROTTLED, &tty->flags))
		goto throttled;

	/* If we aren't interrupt driven and aren't throttled, we always
	 * request a reschedule
	 */
	if (hp->irq == 0)
		poll_mask |= HVC_POLL_READ;

	/* Read data if any */
	for (;;) {
		int count = tty_buffer_request_room(tty, N_INBUF);

		/* If flip is full, just reschedule a later read */
		if (count == 0) {
			poll_mask |= HVC_POLL_READ;
			break;
		}

		n = hp->ops->get_chars(hp->vtermno, buf, count);
		if (n <= 0) {
			/* Hangup the tty when disconnected from host */
			if (n == -EPIPE) {
				spin_unlock_irqrestore(&hp->lock, flags);
				tty_hangup(tty);
				spin_lock_irqsave(&hp->lock, flags);
			} else if ( n == -EAGAIN ) {
				/*
				 * Some back-ends can only ensure a certain min
				 * num of bytes read, which may be > 'count'.
				 * Let the tty clear the flip buff to make room.
				 */
				poll_mask |= HVC_POLL_READ;
			}
			break;
		}
		for (i = 0; i < n; ++i) {
#ifdef CONFIG_MAGIC_SYSRQ
			if (hp->index == hvc_con_driver.index) {
				/* Handle the SysRq Hack */
				/* XXX should support a sequence */
				if (buf[i] == '\x0f') {	/* ^O */
					sysrq_pressed = 1;
					continue;
				} else if (sysrq_pressed) {
					handle_sysrq(buf[i], tty);
					sysrq_pressed = 0;
					continue;
				}
			}
#endif /* CONFIG_MAGIC_SYSRQ */
			tty_insert_flip_char(tty, buf[i], 0);
		}

		read_total += n;
	}
 throttled:
	/* Wakeup write queue if necessary */
	if (hp->do_wakeup) {
		hp->do_wakeup = 0;
		tty_wakeup(tty);
	}
 bail:
	spin_unlock_irqrestore(&hp->lock, flags);

	if (read_total) {
		/* Activity is occurring, so reset the polling backoff value to
		   a minimum for performance. */
		timeout = MIN_TIMEOUT;

		tty_flip_buffer_push(tty);
	}

	return poll_mask;
}

#if defined(CONFIG_XMON) && defined(CONFIG_SMP)
extern cpumask_t cpus_in_xmon;
#else
static const cpumask_t cpus_in_xmon = CPU_MASK_NONE;
#endif

/*
 * This kthread is either polling or interrupt driven.  This is determined by
 * calling hvc_poll() who determines whether a console adapter support
 * interrupts.
 */
static int khvcd(void *unused)
{
	int poll_mask;
	struct hvc_struct *hp;

	set_freezable();
	__set_current_state(TASK_RUNNING);
	do {
		poll_mask = 0;
		hvc_kicked = 0;
		try_to_freeze();
		wmb();
		if (cpus_empty(cpus_in_xmon)) {
			spin_lock(&hvc_structs_lock);
			list_for_each_entry(hp, &hvc_structs, next) {
				poll_mask |= hvc_poll(hp);
			}
			spin_unlock(&hvc_structs_lock);
		} else
			poll_mask |= HVC_POLL_READ;
		if (hvc_kicked)
			continue;
		if (poll_mask & HVC_POLL_WRITE) {
			yield();
			continue;
		}
		set_current_state(TASK_INTERRUPTIBLE);
		if (!hvc_kicked) {
			if (poll_mask == 0)
				schedule();
			else {
				if (timeout < MAX_TIMEOUT)
					timeout += (timeout >> 6) + 1;

				msleep_interruptible(timeout);
			}
		}
		__set_current_state(TASK_RUNNING);
	} while (!kthread_should_stop());

	return 0;
}

static const struct tty_operations hvc_ops = {
	.open = hvc_open,
	.close = hvc_close,
	.write = hvc_write,
	.hangup = hvc_hangup,
	.unthrottle = hvc_unthrottle,
	.write_room = hvc_write_room,
	.chars_in_buffer = hvc_chars_in_buffer,
};

/* callback when the kboject ref count reaches zero. */
static void destroy_hvc_struct(struct kobject *kobj)
{
	struct hvc_struct *hp = container_of(kobj, struct hvc_struct, kobj);
	unsigned long flags;

	spin_lock(&hvc_structs_lock);

	spin_lock_irqsave(&hp->lock, flags);
	list_del(&(hp->next));
	spin_unlock_irqrestore(&hp->lock, flags);

	spin_unlock(&hvc_structs_lock);

	kfree(hp);
}

static struct kobj_type hvc_kobj_type = {
	.release = destroy_hvc_struct,
};

struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
					struct hv_ops *ops, int outbuf_size)
{
	struct hvc_struct *hp;
	int i;

	/* We wait until a driver actually comes along */
	if (!hvc_driver) {
		int err = hvc_init();
		if (err)
			return ERR_PTR(err);
	}

	hp = kmalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
			GFP_KERNEL);
	if (!hp)
		return ERR_PTR(-ENOMEM);

	memset(hp, 0x00, sizeof(*hp));

	hp->vtermno = vtermno;
	hp->irq = irq;
	hp->ops = ops;
	hp->outbuf_size = outbuf_size;
	hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];

	kobject_init(&hp->kobj);
	hp->kobj.ktype = &hvc_kobj_type;

	spin_lock_init(&hp->lock);
	spin_lock(&hvc_structs_lock);

	/*
	 * find index to use:
	 * see if this vterm id matches one registered for console.
	 */
	for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
		if (vtermnos[i] == hp->vtermno &&
		    cons_ops[i] == hp->ops)
			break;

	/* no matching slot, just use a counter */
	if (i >= MAX_NR_HVC_CONSOLES)
		i = ++last_hvc;

	hp->index = i;

	list_add_tail(&(hp->next), &hvc_structs);
	spin_unlock(&hvc_structs_lock);

	return hp;
}

int __devexit hvc_remove(struct hvc_struct *hp)
{
	unsigned long flags;
	struct kobject *kobjp;
	struct tty_struct *tty;

	spin_lock_irqsave(&hp->lock, flags);
	tty = hp->tty;
	kobjp = &hp->kobj;

	if (hp->index < MAX_NR_HVC_CONSOLES)
		vtermnos[hp->index] = -1;

	/* Don't whack hp->irq because tty_hangup() will need to free the irq. */

	spin_unlock_irqrestore(&hp->lock, flags);

	/*
	 * We 'put' the instance that was grabbed when the kobject instance
	 * was initialized using kobject_init().  Let the last holder of this
	 * kobject cause it to be removed, which will probably be the tty_hangup
	 * below.
	 */
	kobject_put(kobjp);

	/*
	 * This function call will auto chain call hvc_hangup.  The tty should
	 * always be valid at this time unless a simultaneous tty close already
	 * cleaned up the hvc_struct.
	 */
	if (tty)
		tty_hangup(tty);
	return 0;
}

/* Driver initialization: called as soon as someone uses hvc_alloc(). */
static int hvc_init(void)
{
	struct tty_driver *drv;
	int err;

	/* We need more than hvc_count adapters due to hotplug additions. */
	drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
	if (!drv) {
		err = -ENOMEM;
		goto out;
	}

	drv->owner = THIS_MODULE;
	drv->driver_name = "hvc";
	drv->name = "hvc";
	drv->major = HVC_MAJOR;
	drv->minor_start = HVC_MINOR;
	drv->type = TTY_DRIVER_TYPE_SYSTEM;
	drv->init_termios = tty_std_termios;
	drv->flags = TTY_DRIVER_REAL_RAW;
	tty_set_operations(drv, &hvc_ops);

	/* Always start the kthread because there can be hotplug vty adapters
	 * added later. */
	hvc_task = kthread_run(khvcd, NULL, "khvcd");
	if (IS_ERR(hvc_task)) {
		printk(KERN_ERR "Couldn't create kthread for console.\n");
		err = PTR_ERR(hvc_task);
		goto put_tty;
	}

	err = tty_register_driver(drv);
	if (err) {
		printk(KERN_ERR "Couldn't register hvc console driver\n");
		goto stop_thread;
	}

	/* FIXME: This mb() seems completely random.  Remove it. */
	mb();
	hvc_driver = drv;
	return 0;

put_tty:
	put_tty_driver(hvc_driver);
stop_thread:
	kthread_stop(hvc_task);
	hvc_task = NULL;
out:
	return err;
}

/* This isn't particularly necessary due to this being a console driver
 * but it is nice to be thorough.
 */
static void __exit hvc_exit(void)
{
	if (hvc_driver) {
		kthread_stop(hvc_task);

		tty_unregister_driver(hvc_driver);
		/* return tty_struct instances allocated in hvc_init(). */
		put_tty_driver(hvc_driver);
		unregister_console(&hvc_con_driver);
	}
}
module_exit(hvc_exit);