line.c

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/*
 * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include "linux/irqreturn.h"
#include "linux/kd.h"
#include "chan_kern.h"
#include "irq_kern.h"
#include "irq_user.h"
#include "os.h"

#define LINE_BUFSIZE 4096

static irqreturn_t line_interrupt(int irq, void *data)
{
	struct chan *chan = data;
	struct line *line = chan->line;
	struct tty_struct *tty = line->tty;

	if (line)
		chan_interrupt(&line->chan_list, &line->task, tty, irq);
	return IRQ_HANDLED;
}

static void line_timer_cb(struct work_struct *work)
{
	struct line *line = container_of(work, struct line, task.work);

	if (!line->throttled)
		chan_interrupt(&line->chan_list, &line->task, line->tty,
			       line->driver->read_irq);
}

/*
 * Returns the free space inside the ring buffer of this line.
 *
 * Should be called while holding line->lock (this does not modify data).
 */
static int write_room(struct line *line)
{
	int n;

	if (line->buffer == NULL)
		return LINE_BUFSIZE - 1;

	/* This is for the case where the buffer is wrapped! */
	n = line->head - line->tail;

	if (n <= 0)
		n = LINE_BUFSIZE + n; /* The other case */
	return n - 1;
}

int line_write_room(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;
	unsigned long flags;
	int room;

	if (tty->stopped)
		return 0;

	spin_lock_irqsave(&line->lock, flags);
	room = write_room(line);
	spin_unlock_irqrestore(&line->lock, flags);

	/*XXX: Warning to remove */
	if (0 == room)
		printk(KERN_DEBUG "%s: %s: no room left in buffer\n",
		       __FUNCTION__,tty->name);
	return room;
}

int line_chars_in_buffer(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;
	unsigned long flags;
	int ret;

	spin_lock_irqsave(&line->lock, flags);

	/*write_room subtracts 1 for the needed NULL, so we readd it.*/
	ret = LINE_BUFSIZE - (write_room(line) + 1);
	spin_unlock_irqrestore(&line->lock, flags);

	return ret;
}

/*
 * This copies the content of buf into the circular buffer associated with
 * this line.
 * The return value is the number of characters actually copied, i.e. the ones
 * for which there was space: this function is not supposed to ever flush out
 * the circular buffer.
 *
 * Must be called while holding line->lock!
 */
static int buffer_data(struct line *line, const char *buf, int len)
{
	int end, room;

	if (line->buffer == NULL) {
		line->buffer = kmalloc(LINE_BUFSIZE, GFP_ATOMIC);
		if (line->buffer == NULL) {
			printk(KERN_ERR "buffer_data - atomic allocation "
			       "failed\n");
			return 0;
		}
		line->head = line->buffer;
		line->tail = line->buffer;
	}

	room = write_room(line);
	len = (len > room) ? room : len;

	end = line->buffer + LINE_BUFSIZE - line->tail;

	if (len < end) {
		memcpy(line->tail, buf, len);
		line->tail += len;
	}
	else {
		/* The circular buffer is wrapping */
		memcpy(line->tail, buf, end);
		buf += end;
		memcpy(line->buffer, buf, len - end);
		line->tail = line->buffer + len - end;
	}

	return len;
}

/*
 * Flushes the ring buffer to the output channels. That is, write_chan is
 * called, passing it line->head as buffer, and an appropriate count.
 *
 * On exit, returns 1 when the buffer is empty,
 * 0 when the buffer is not empty on exit,
 * and -errno when an error occurred.
 *
 * Must be called while holding line->lock!*/
static int flush_buffer(struct line *line)
{
	int n, count;

	if ((line->buffer == NULL) || (line->head == line->tail))
		return 1;

	if (line->tail < line->head) {
		/* line->buffer + LINE_BUFSIZE is the end of the buffer! */
		count = line->buffer + LINE_BUFSIZE - line->head;

		n = write_chan(&line->chan_list, line->head, count,
			       line->driver->write_irq);
		if (n < 0)
			return n;
		if (n == count) {
			/*
			 * We have flushed from ->head to buffer end, now we
			 * must flush only from the beginning to ->tail.
			 */
			line->head = line->buffer;
		} else {
			line->head += n;
			return 0;
		}
	}

	count = line->tail - line->head;
	n = write_chan(&line->chan_list, line->head, count,
		       line->driver->write_irq);

	if (n < 0)
		return n;

	line->head += n;
	return line->head == line->tail;
}

void line_flush_buffer(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;
	unsigned long flags;
	int err;

	/*XXX: copied from line_write, verify if it is correct!*/
	if (tty->stopped)
		return;

	spin_lock_irqsave(&line->lock, flags);
	err = flush_buffer(line);
	spin_unlock_irqrestore(&line->lock, flags);
}

/*
 * We map both ->flush_chars and ->put_char (which go in pair) onto
 * ->flush_buffer and ->write. Hope it's not that bad.
 */
void line_flush_chars(struct tty_struct *tty)
{
	line_flush_buffer(tty);
}

void line_put_char(struct tty_struct *tty, unsigned char ch)
{
	line_write(tty, &ch, sizeof(ch));
}

int line_write(struct tty_struct *tty, const unsigned char *buf, int len)
{
	struct line *line = tty->driver_data;
	unsigned long flags;
	int n, ret = 0;

	if (tty->stopped)
		return 0;

	spin_lock_irqsave(&line->lock, flags);
	if (line->head != line->tail)
		ret = buffer_data(line, buf, len);
	else {
		n = write_chan(&line->chan_list, buf, len,
			       line->driver->write_irq);
		if (n < 0) {
			ret = n;
			goto out_up;
		}

		len -= n;
		ret += n;
		if (len > 0)
			ret += buffer_data(line, buf + n, len);
	}
out_up:
	spin_unlock_irqrestore(&line->lock, flags);
	return ret;
}

void line_set_termios(struct tty_struct *tty, struct ktermios * old)
{
	/* nothing */
}

static const struct {
	int  cmd;
	char *level;
	char *name;
} tty_ioctls[] = {
	/* don't print these, they flood the log ... */
	{ TCGETS,      NULL,       "TCGETS"      },
	{ TCSETS,      NULL,       "TCSETS"      },
	{ TCSETSW,     NULL,       "TCSETSW"     },
	{ TCFLSH,      NULL,       "TCFLSH"      },
	{ TCSBRK,      NULL,       "TCSBRK"      },

	/* general tty stuff */
	{ TCSETSF,     KERN_DEBUG, "TCSETSF"     },
	{ TCGETA,      KERN_DEBUG, "TCGETA"      },
	{ TIOCMGET,    KERN_DEBUG, "TIOCMGET"    },
	{ TCSBRKP,     KERN_DEBUG, "TCSBRKP"     },
	{ TIOCMSET,    KERN_DEBUG, "TIOCMSET"    },

	/* linux-specific ones */
	{ TIOCLINUX,   KERN_INFO,  "TIOCLINUX"   },
	{ KDGKBMODE,   KERN_INFO,  "KDGKBMODE"   },
	{ KDGKBTYPE,   KERN_INFO,  "KDGKBTYPE"   },
	{ KDSIGACCEPT, KERN_INFO,  "KDSIGACCEPT" },
};

int line_ioctl(struct tty_struct *tty, struct file * file,
	       unsigned int cmd, unsigned long arg)
{
	int ret;
	int i;

	ret = 0;
	switch(cmd) {
#ifdef TIOCGETP
	case TIOCGETP:
	case TIOCSETP:
	case TIOCSETN:
#endif
#ifdef TIOCGETC
	case TIOCGETC:
	case TIOCSETC:
#endif
#ifdef TIOCGLTC
	case TIOCGLTC:
	case TIOCSLTC:
#endif
	case TCGETS:
	case TCSETSF:
	case TCSETSW:
	case TCSETS:
	case TCGETA:
	case TCSETAF:
	case TCSETAW:
	case TCSETA:
	case TCXONC:
	case TCFLSH:
	case TIOCOUTQ:
	case TIOCINQ:
	case TIOCGLCKTRMIOS:
	case TIOCSLCKTRMIOS:
	case TIOCPKT:
	case TIOCGSOFTCAR:
	case TIOCSSOFTCAR:
		return -ENOIOCTLCMD;
#if 0
	case TCwhatever:
		/* do something */
		break;
#endif
	default:
		for (i = 0; i < ARRAY_SIZE(tty_ioctls); i++)
			if (cmd == tty_ioctls[i].cmd)
				break;
		if (i == ARRAY_SIZE(tty_ioctls)) {
			printk(KERN_ERR "%s: %s: unknown ioctl: 0x%x\n",
			       __FUNCTION__, tty->name, cmd);
		}
		ret = -ENOIOCTLCMD;
		break;
	}
	return ret;
}

void line_throttle(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;

	deactivate_chan(&line->chan_list, line->driver->read_irq);
	line->throttled = 1;
}

void line_unthrottle(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;

	line->throttled = 0;
	chan_interrupt(&line->chan_list, &line->task, tty,
		       line->driver->read_irq);

	/*
	 * Maybe there is enough stuff pending that calling the interrupt
	 * throttles us again.  In this case, line->throttled will be 1
	 * again and we shouldn't turn the interrupt back on.
	 */
	if (!line->throttled)
		reactivate_chan(&line->chan_list, line->driver->read_irq);
}

static irqreturn_t line_write_interrupt(int irq, void *data)
{
	struct chan *chan = data;
	struct line *line = chan->line;
	struct tty_struct *tty = line->tty;
	int err;

	/*
	 * Interrupts are disabled here because we registered the interrupt with
	 * IRQF_DISABLED (see line_setup_irq).
	 */

	spin_lock(&line->lock);
	err = flush_buffer(line);
	if (err == 0) {
		return IRQ_NONE;
	} else if (err < 0) {
		line->head = line->buffer;
		line->tail = line->buffer;
	}
	spin_unlock(&line->lock);

	if (tty == NULL)
		return IRQ_NONE;

	if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags) &&
	   (tty->ldisc.write_wakeup != NULL))
		(tty->ldisc.write_wakeup)(tty);

	/*
	 * BLOCKING mode
	 * In blocking mode, everything sleeps on tty->write_wait.
	 * Sleeping in the console driver would break non-blocking
	 * writes.
	 */

	if (waitqueue_active(&tty->write_wait))
		wake_up_interruptible(&tty->write_wait);
	return IRQ_HANDLED;
}

int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
{
	const struct line_driver *driver = line->driver;
	int err = 0, flags = IRQF_DISABLED | IRQF_SHARED | IRQF_SAMPLE_RANDOM;

	if (input)
		err = um_request_irq(driver->read_irq, fd, IRQ_READ,
				       line_interrupt, flags,
				       driver->read_irq_name, data);
	if (err)
		return err;
	if (output)
		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
					line_write_interrupt, flags,
					driver->write_irq_name, data);
	line->have_irq = 1;
	return err;
}

/*
 * Normally, a driver like this can rely mostly on the tty layer
 * locking, particularly when it comes to the driver structure.
 * However, in this case, mconsole requests can come in "from the
 * side", and race with opens and closes.
 *
 * mconsole config requests will want to be sure the device isn't in
 * use, and get_config, open, and close will want a stable
 * configuration.  The checking and modification of the configuration
 * is done under a spinlock.  Checking whether the device is in use is
 * line->tty->count > 1, also under the spinlock.
 *
 * tty->count serves to decide whether the device should be enabled or
 * disabled on the host.  If it's equal to 1, then we are doing the
 * first open or last close.  Otherwise, open and close just return.
 */

int line_open(struct line *lines, struct tty_struct *tty)
{
	struct line *line = &lines[tty->index];
	int err = -ENODEV;

	spin_lock(&line->count_lock);
	if (!line->valid)
		goto out_unlock;

	err = 0;
	if (tty->count > 1)
		goto out_unlock;

	spin_unlock(&line->count_lock);

	tty->driver_data = line;
	line->tty = tty;