hvcs.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 1,667 行 · 第 1/4 页

	 * If there wasn't any pi when the device was added it doesn't meant
	 * there isn't any now.  This driver isn't notified when a new partner
	 * vty is added to a vty-server so we discover changes on our own.
	 * Please see comments in hvcs_register_connection() for justification
	 * of this bizarre code.
	 */
	retval = hvcs_register_connection(unit_address,
			hvcsd->p_partition_ID,
			hvcsd->p_unit_address);
	if (!retval) {
		hvcsd->connected = 1;
		return 0;
	} else if (retval != -EINVAL)
		return retval;

	/*
	 * As per the spec re-get the pi and try again if -EINVAL after the
	 * first connection attempt.
	 */
	if (hvcs_get_pi(hvcsd))
		return -ENOMEM;

	if (!hvcs_has_pi(hvcsd))
		return -ENODEV;

	retval = hvcs_register_connection(unit_address,
			hvcsd->p_partition_ID,
			hvcsd->p_unit_address);
	if (retval != -EINVAL) {
		hvcsd->connected = 1;
		return retval;
	}

	/*
	 * EBUSY is the most likely scenario though the vty could have been
	 * removed or there really could be an hcall error due to the parameter
	 * data but thanks to ambiguous firmware return codes we can't really
	 * tell.
	 */
	printk(KERN_INFO "HVCS: vty-server or partner"
			" vty is busy.  Try again later.\n");
	return -EBUSY;
}

/* This function must be called with the hvcsd->lock held */
static void hvcs_partner_free(struct hvcs_struct *hvcsd)
{
	int retval;
	do {
		retval = hvcs_free_connection(hvcsd->vdev->unit_address);
	} while (retval == -EBUSY);
	hvcsd->connected = 0;
}

/* This helper function must be called WITHOUT the hvcsd->lock held */
static int hvcs_enable_device(struct hvcs_struct *hvcsd, uint32_t unit_address,
		unsigned int irq, struct vio_dev *vdev)
{
	unsigned long flags;
	int rc;

	/*
	 * It is possible that the vty-server was removed between the time that
	 * the conn was registered and now.
	 */
	if (!(rc = request_irq(irq, &hvcs_handle_interrupt,
				SA_INTERRUPT, "ibmhvcs", hvcsd))) {
		/*
		 * It is possible the vty-server was removed after the irq was
		 * requested but before we have time to enable interrupts.
		 */
		if (vio_enable_interrupts(vdev) == H_Success)
			return 0;
		else {
			printk(KERN_ERR "HVCS: int enable failed for"
					" vty-server@%X.\n", unit_address);
			free_irq(irq, hvcsd);
		}
	} else
		printk(KERN_ERR "HVCS: irq req failed for"
				" vty-server@%X.\n", unit_address);

	spin_lock_irqsave(&hvcsd->lock, flags);
	hvcs_partner_free(hvcsd);
	spin_unlock_irqrestore(&hvcsd->lock, flags);

	return rc;

}

/*
 * This always increments the kobject ref count if the call is successful.
 * Please remember to dec when you are done with the instance.
 *
 * NOTICE: Do NOT hold either the hvcs_struct.lock or hvcs_structs_lock when
 * calling this function or you will get deadlock.
 */
struct hvcs_struct *hvcs_get_by_index(int index)
{
	struct hvcs_struct *hvcsd = NULL;
	unsigned long flags;

	spin_lock(&hvcs_structs_lock);
	/* We can immediately discard OOB requests */
	if (index >= 0 && index < HVCS_MAX_SERVER_ADAPTERS) {
		list_for_each_entry(hvcsd, &hvcs_structs, next) {
			spin_lock_irqsave(&hvcsd->lock, flags);
			if (hvcsd->index == index) {
				kobject_get(&hvcsd->kobj);
				spin_unlock_irqrestore(&hvcsd->lock, flags);
				spin_unlock(&hvcs_structs_lock);
				return hvcsd;
			}
			spin_unlock_irqrestore(&hvcsd->lock, flags);
		}
		hvcsd = NULL;
	}

	spin_unlock(&hvcs_structs_lock);
	return hvcsd;
}

/*
 * This is invoked via the tty_open interface when a user app connects to the
 * /dev node.
 */
static int hvcs_open(struct tty_struct *tty, struct file *filp)
{
	struct hvcs_struct *hvcsd;
	int rc, retval = 0;
	unsigned long flags;
	unsigned int irq;
	struct vio_dev *vdev;
	unsigned long unit_address;
	struct kobject *kobjp;

	if (tty->driver_data)
		goto fast_open;

	/*
	 * Is there a vty-server that shares the same index?
	 * This function increments the kobject index.
	 */
	if (!(hvcsd = hvcs_get_by_index(tty->index))) {
		printk(KERN_WARNING "HVCS: open failed, no device associated"
				" with tty->index %d.\n", tty->index);
		return -ENODEV;
	}

	spin_lock_irqsave(&hvcsd->lock, flags);

	if (hvcsd->connected == 0)
		if ((retval = hvcs_partner_connect(hvcsd)))
			goto error_release;

	hvcsd->open_count = 1;
	hvcsd->tty = tty;
	tty->driver_data = hvcsd;

	/*
	 * Set this driver to low latency so that we actually have a chance at
	 * catching a throttled TTY after we flip_buffer_push.  Otherwise the
	 * flush_to_async may not execute until after the kernel_thread has
	 * yielded and resumed the next flip_buffer_push resulting in data
	 * loss.
	 */
	tty->low_latency = 1;

	memset(&hvcsd->buffer[0], 0x00, HVCS_BUFF_LEN);

	/*
	 * Save these in the spinlock for the enable operations that need them
	 * outside of the spinlock.
	 */
	irq = hvcsd->vdev->irq;
	vdev = hvcsd->vdev;
	unit_address = hvcsd->vdev->unit_address;

	hvcsd->todo_mask |= HVCS_SCHED_READ;
	spin_unlock_irqrestore(&hvcsd->lock, flags);

	/*
	 * This must be done outside of the spinlock because it requests irqs
	 * and will grab the spinlock and free the connection if it fails.
	 */
	if (((rc = hvcs_enable_device(hvcsd, unit_address, irq, vdev)))) {
		kobject_put(&hvcsd->kobj);
		printk(KERN_WARNING "HVCS: enable device failed.\n");
		return rc;
	}

	goto open_success;

fast_open:
	hvcsd = tty->driver_data;

	spin_lock_irqsave(&hvcsd->lock, flags);
	if (!kobject_get(&hvcsd->kobj)) {
		spin_unlock_irqrestore(&hvcsd->lock, flags);
		printk(KERN_ERR "HVCS: Kobject of open"
			" hvcs doesn't exist.\n");
		return -EFAULT; /* Is this the right return value? */
	}

	hvcsd->open_count++;

	hvcsd->todo_mask |= HVCS_SCHED_READ;
	spin_unlock_irqrestore(&hvcsd->lock, flags);
open_success:
	hvcs_kick();

	printk(KERN_INFO "HVCS: vty-server@%X connection opened.\n",
		hvcsd->vdev->unit_address );

	return 0;

error_release:
	kobjp = &hvcsd->kobj;
	spin_unlock_irqrestore(&hvcsd->lock, flags);
	kobject_put(&hvcsd->kobj);

	printk(KERN_WARNING "HVCS: partner connect failed.\n");
	return retval;
}

static void hvcs_close(struct tty_struct *tty, struct file *filp)
{
	struct hvcs_struct *hvcsd;
	unsigned long flags;
	struct kobject *kobjp;
	int irq = NO_IRQ;

	/*
	 * Is someone trying to close the file associated with this device after
	 * we have hung up?  If so tty->driver_data wouldn't be valid.
	 */
	if (tty_hung_up_p(filp))
		return;

	/*
	 * No driver_data means that this close was probably issued after a
	 * failed hvcs_open by the tty layer's release_dev() api and we can just
	 * exit cleanly.
	 */
	if (!tty->driver_data)
		return;

	hvcsd = tty->driver_data;

	spin_lock_irqsave(&hvcsd->lock, flags);
	kobjp = &hvcsd->kobj;
	if (--hvcsd->open_count == 0) {

		vio_disable_interrupts(hvcsd->vdev);

		/*
		 * NULL this early so that the kernel_thread doesn't try to
		 * execute any operations on the TTY even though it is obligated
		 * to deliver any pending I/O to the hypervisor.
		 */
		hvcsd->tty = NULL;

		irq = hvcsd->vdev->irq;
		spin_unlock_irqrestore(&hvcsd->lock, flags);

		tty_wait_until_sent(tty, HVCS_CLOSE_WAIT);

		/*
		 * This line is important because it tells hvcs_open that this
		 * device needs to be re-configured the next time hvcs_open is
		 * called.
		 */
		tty->driver_data = NULL;

		free_irq(irq, hvcsd);
		kobject_put(kobjp);
		return;
	} else if (hvcsd->open_count < 0) {
		printk(KERN_ERR "HVCS: vty-server@%X open_count: %d"
				" is missmanaged.\n",
		hvcsd->vdev->unit_address, hvcsd->open_count);
	}

	spin_unlock_irqrestore(&hvcsd->lock, flags);
	kobject_put(kobjp);
}

static void hvcs_hangup(struct tty_struct * tty)
{
	struct hvcs_struct *hvcsd = tty->driver_data;
	unsigned long flags;
	int temp_open_count;
	struct kobject *kobjp;
	int irq = NO_IRQ;

	spin_lock_irqsave(&hvcsd->lock, flags);
	/* Preserve this so that we know how many kobject refs to put */
	temp_open_count = hvcsd->open_count;

	/*
	 * Don't kobject put inside the spinlock because the destruction
	 * callback may use the spinlock and it may get called before the
	 * spinlock has been released.  Get a pointer to the kobject and
	 * kobject_put on that after releasing the spinlock.
	 */
	kobjp = &hvcsd->kobj;

	vio_disable_interrupts(hvcsd->vdev);

	hvcsd->todo_mask = 0;

	/* I don't think the tty needs the hvcs_struct pointer after a hangup */
	hvcsd->tty->driver_data = NULL;
	hvcsd->tty = NULL;

	hvcsd->open_count = 0;

	/* This will drop any buffered data on the floor which is OK in a hangup
	 * scenario. */
	memset(&hvcsd->buffer[0], 0x00, HVCS_BUFF_LEN);
	hvcsd->chars_in_buffer = 0;

	irq = hvcsd->vdev->irq;

	spin_unlock_irqrestore(&hvcsd->lock, flags);

	free_irq(irq, hvcsd);

	/*
	 * We need to kobject_put() for every open_count we have since the
	 * tty_hangup() function doesn't invoke a close per open connection on a
	 * non-console device.
	 */
	while(temp_open_count) {
		--temp_open_count;
		/*
		 * The final put will trigger destruction of the hvcs_struct.
		 * NOTE:  If this hangup was signaled from user space then the
		 * final put will never happen.
		 */
		kobject_put(kobjp);
	}
}

/*
 * NOTE: This is almost always from_user since user level apps interact with the
 * /dev nodes. I'm trusting that if hvcs_write gets called and interrupted by
 * hvcs_remove (which removes the target device and executes tty_hangup()) that
 * tty_hangup will allow hvcs_write time to complete execution before it
 * terminates our device.
 */
static int hvcs_write(struct tty_struct *tty, int from_user,
		const unsigned char *buf, int count)
{
	struct hvcs_struct *hvcsd = tty->driver_data;
	unsigned int unit_address;
	unsigned char *charbuf;
	unsigned long flags;
	int total_sent = 0;
	int tosend = 0;
	int result = 0;

	/*
	 * If they don't check the return code off of their open they may
	 * attempt this even if there is no connected device.
	 */
	if (!hvcsd)
		return -ENODEV;

	/* Reasonable size to prevent user level flooding */
	if (count > HVCS_MAX_FROM_USER) {
		printk(KERN_WARNING "HVCS write: count being truncated to"
				" HVCS_MAX_FROM_USER.\n");
		count = HVCS_MAX_FROM_USER;
	}

	if (!from_user)
		charbuf = (unsigned char *)buf;
	else {
		charbuf = kmalloc(count, GFP_KERNEL);
		if (!charbuf) {
			printk(KERN_WARNING "HVCS: write -ENOMEM.\n");
			return -ENOMEM;
		}

		if (copy_from_user(charbuf, buf, count)) {
			kfree(charbuf);
			printk(KERN_WARNING "HVCS: write -EFAULT.\n");
			return -EFAULT;
		}
	}

	spin_lock_irqsave(&hvcsd->lock, flags);

	/*
	 * Somehow an open succedded but the device was removed or the
	 * connection terminated between the vty-server and partner vty during
	 * the middle of a write operation?  This is a crummy place to do this
	 * but we want to keep it all in the spinlock.
	 */
	if (hvcsd->open_count <= 0) {
		spin_unlock_irqrestore(&hvcsd->lock, flags);
		if (from_user)
			kfree(charbuf);
		return -ENODEV;
	}

	unit_address = hvcsd->vdev->unit_address;

	while (count > 0) {
		tosend = min(count, (HVCS_BUFF_LEN - hvcsd->chars_in_buffer));
		/*
		 * No more space, this probably means that the last call to
		 * hvcs_write() didn't succeed and the buffer was filled up.
		 */
		if (!tosend)
			break;