hvc_console.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 880 行 · 第 1/2 页

/*
 * Copyright (C) 2001 Anton Blanchard <[e-mail]>, IBM
 * Copyright (C) 2001 Paul Mackerras <[e-mail]>, IBM
 * Copyright (C) 2004 Benjamin Herrenschmidt <[e-mail]>, IBM Corp.
 * Copyright (C) 2004 IBM Corporation
 *
 * Additional Author(s):
 *  Ryan S. Arnold <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 */

#include <linux/console.h>
#include <linux/cpumask.h>
#include <linux/init.h>
#include <linux/kbd_kern.h>
#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/kthread.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/major.h>
#include <linux/sysrq.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include <asm/hvconsole.h>
#include <asm/vio.h>

#define HVC_MAJOR	229
#define HVC_MINOR	0

#define TIMEOUT		((HZ + 99) / 100)

/*
 * Wait this long per iteration while trying to push buffered data to the
 * hypervisor before allowing the tty to complete a close operation.
 */
#define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */

/*
 * The Linux TTY code does not support dynamic addition of tty derived devices
 * so we need to know how many tty devices we might need when space is allocated
 * for the tty device.  Since this driver supports hotplug of vty adapters we
 * need to make sure we have enough allocated.
 */
#define HVC_ALLOC_TTY_ADAPTERS	8

static struct tty_driver *hvc_driver;
#ifdef CONFIG_MAGIC_SYSRQ
static int sysrq_pressed;
#endif

#define N_OUTBUF	16
#define N_INBUF		16

#define __ALIGNED__	__attribute__((__aligned__(8)))

struct hvc_struct {
	spinlock_t lock;
	int index;
	struct tty_struct *tty;
	unsigned int count;
	int do_wakeup;
	char outbuf[N_OUTBUF] __ALIGNED__;
	int n_outbuf;
	uint32_t vtermno;
	int irq_requested;
	int irq;
	struct list_head next;
	struct kobject kobj; /* ref count & hvc_struct lifetime */
	struct vio_dev *vdev;
};

/* dynamic list of hvc_struct instances */
static struct list_head hvc_structs = LIST_HEAD_INIT(hvc_structs);

/*
 * Protect the list of hvc_struct instances from inserts and removals during
 * list traversal.
 */
static spinlock_t hvc_structs_lock = SPIN_LOCK_UNLOCKED;

/*
 * Initial console vtermnos for console API usage prior to full console
 * initialization.  Any vty adapter outside this range will not have usable
 * console interfaces but can still be used as a tty device.  This has to be
 * static because kmalloc will not work during early console init.
 */
static uint32_t vtermnos[MAX_NR_HVC_CONSOLES];

/* Used for accounting purposes */
static int num_vterms = 0;

static struct task_struct *hvc_task;

/*
 * This value is used to associate a tty->index value to a hvc_struct based
 * upon order of exposure via hvc_probe().
 */
static int hvc_count = -1;

/* Picks up late kicks after list walk but before schedule() */
static int hvc_kicked;

/* Wake the sleeping khvcd */
static void hvc_kick(void)
{
	hvc_kicked = 1;
	wake_up_process(hvc_task);
}

/*
 * NOTE: This API isn't used if the console adapter doesn't support interrupts.
 * In this case the console is poll driven.
 */
static irqreturn_t hvc_handle_interrupt(int irq, void *dev_instance, struct pt_regs *regs)
{
	hvc_kick();
	return IRQ_HANDLED;
}

static void hvc_unthrottle(struct tty_struct *tty)
{
	hvc_kick();
}

/*
 * Do not call this function with either the hvc_strucst_lock or the hvc_struct
 * lock held.  If successful, this function increments the kobject reference
 * count against the target hvc_struct so it should be released when finished.
 */
struct hvc_struct *hvc_get_by_index(int index)
{
	struct hvc_struct *hp;
	unsigned long flags;

	spin_lock(&hvc_structs_lock);

	list_for_each_entry(hp, &hvc_structs, next) {
		spin_lock_irqsave(&hp->lock, flags);
		if (hp->index == index) {
			kobject_get(&hp->kobj);
			spin_unlock_irqrestore(&hp->lock, flags);
			spin_unlock(&hvc_structs_lock);
			return hp;
		}
		spin_unlock_irqrestore(&hp->lock, flags);
	}
	hp = NULL;

	spin_unlock(&hvc_structs_lock);
	return hp;
}

/*
 * The TTY interface won't be used until after the vio layer has exposed the vty
 * adapter to the kernel.
 */
static int hvc_open(struct tty_struct *tty, struct file * filp)
{
	struct hvc_struct *hp;
	unsigned long flags;
	int irq = NO_IRQ;
	int rc = 0;
	struct kobject *kobjp;

	/* Auto increments kobject reference if found. */
	if (!(hp = hvc_get_by_index(tty->index))) {
		printk(KERN_WARNING "hvc_console: tty open failed, no vty associated with tty.\n");
		return -ENODEV;
	}

	spin_lock_irqsave(&hp->lock, flags);
	/* Check and then increment for fast path open. */
	if (hp->count++ > 0) {
		spin_unlock_irqrestore(&hp->lock, flags);
		hvc_kick();
		return 0;
	} /* else count == 0 */

	tty->driver_data = hp;
	hp->tty = tty;
	/* Save for request_irq outside of spin_lock. */
	irq = hp->irq;
	if (irq != NO_IRQ)
		hp->irq_requested = 1;

	kobjp = &hp->kobj;

	spin_unlock_irqrestore(&hp->lock, flags);
	/* check error, fallback to non-irq */
	if (irq != NO_IRQ)
		rc = request_irq(irq, hvc_handle_interrupt, SA_INTERRUPT, "hvc_console", hp);

	/*
	 * If the request_irq() fails and we return an error.  The tty layer
	 * will call hvc_close() after a failed open but we don't want to clean
	 * up there so we'll clean up here and clear out the previously set
	 * tty fields and return the kobject reference.
	 */
	if (rc) {
		spin_lock_irqsave(&hp->lock, flags);
		hp->tty = NULL;
		hp->irq_requested = 0;
		spin_unlock_irqrestore(&hp->lock, flags);
		tty->driver_data = NULL;
		kobject_put(kobjp);
	}
	/* Force wakeup of the polling thread */
	hvc_kick();

	return rc;
}

static void hvc_close(struct tty_struct *tty, struct file * filp)
{
	struct hvc_struct *hp;
	struct kobject *kobjp;
	int irq = NO_IRQ;
	unsigned long flags;

	if (tty_hung_up_p(filp))
		return;

	/*
	 * No driver_data means that this close was issued after a failed
	 * hvcs_open by the tty layer's release_dev() function and we can just
	 * exit cleanly because the kobject reference wasn't made.
	 */
	if (!tty->driver_data)
		return;

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

	kobjp = &hp->kobj;
	if (--hp->count == 0) {
		if (hp->irq_requested)
			irq = hp->irq;
		hp->irq_requested = 0;

		/* We are done with the tty pointer now. */
		hp->tty = NULL;
		spin_unlock_irqrestore(&hp->lock, flags);

		/*
		 * Chain calls chars_in_buffer() and returns immediately if
		 * there is no buffered data otherwise sleeps on a wait queue
		 * waking periodically to check chars_in_buffer().
		 */
		tty_wait_until_sent(tty, HVC_CLOSE_WAIT);

		/*
		 * Since the line disc doesn't block writes during tty close
		 * operations we'll set driver_data to NULL and then make sure
		 * to check tty->driver_data for NULL in hvc_write().
		 */
		tty->driver_data = NULL;

		if (irq != NO_IRQ)
			free_irq(irq, hp);

	} else {
		if (hp->count < 0)
			printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
				hp->vtermno, hp->count);
		spin_unlock_irqrestore(&hp->lock, flags);
	}

	kobject_put(kobjp);
}

static void hvc_hangup(struct tty_struct *tty)
{
	struct hvc_struct *hp = tty->driver_data;
	unsigned long flags;
	int irq = NO_IRQ;
	int temp_open_count;
	struct kobject *kobjp;

	spin_lock_irqsave(&hp->lock, flags);
	kobjp = &hp->kobj;
	temp_open_count = hp->count;
	hp->count = 0;
	hp->n_outbuf = 0;
	hp->tty = NULL;
	if (hp->irq_requested)
		/* Saved for use outside of spin_lock. */
		irq = hp->irq;
	hp->irq_requested = 0;
	spin_unlock_irqrestore(&hp->lock, flags);
	if (irq != NO_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 = hvc_put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
	if (n <= 0) {
		if (n == 0)
			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 inline int __hvc_write_user(struct hvc_struct *hp,
				   const unsigned char *buf, int count)
{
	char *tbuf, *p;
	int tbsize, rsize, written = 0;
	unsigned long flags;

	tbsize = min(count, (int)PAGE_SIZE);
	if (!(tbuf = kmalloc(tbsize, GFP_KERNEL)))
		return -ENOMEM;

	while ((rsize = count - written) > 0) {
		int wsize;
		if (rsize > tbsize)
			rsize = tbsize;

		p = tbuf;
		rsize -= copy_from_user(p, buf, rsize);
		if (!rsize) {
			if (written == 0)
				written = -EFAULT;
			break;
		}
		buf += rsize;

		spin_lock_irqsave(&hp->lock, flags);

		/* Push pending writes: make some room in buffer */
		if (hp->n_outbuf > 0)
			hvc_push(hp);

		for (wsize = N_OUTBUF - hp->n_outbuf; rsize && wsize;
		     wsize = N_OUTBUF - hp->n_outbuf) {
			if (wsize > rsize)
				wsize = rsize;
			memcpy(hp->outbuf + hp->n_outbuf, p, wsize);
			hp->n_outbuf += wsize;
			hvc_push(hp);
			rsize -= wsize;
			p += wsize;
			written += wsize;
		}
		spin_unlock_irqrestore(&hp->lock, flags);

		if (rsize)
			break;

		if (count < tbsize)
			tbsize = count;
	}

	kfree(tbuf);

	return written;
}

static inline int __hvc_write_kernel(struct hvc_struct *hp,
				   const unsigned char *buf, int count)
{
	unsigned long flags;
	int rsize, written = 0;

	spin_lock_irqsave(&hp->lock, flags);

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

	while (count > 0 && (rsize = N_OUTBUF - 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);

	return written;
}
static int hvc_write(struct tty_struct *tty, int from_user,
		     const unsigned char *buf, int count)
{
	struct hvc_struct *hp = tty->driver_data;
	int written;

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

	if (from_user)
		written = __hvc_write_user(hp, buf, count);
	else
		written = __hvc_write_kernel(hp, buf, count);

	/*
	 * Racy, but harmless, kick thread if there is still pending data.
	 * There really is nothing wrong with kicking the thread, even if there
	 * is no buffered data.
	 */
	if (hp->n_outbuf)