path: root/arch/um/drivers/line.c

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

#include "linux/irqreturn.h"
#include "linux/kd.h"
#include "linux/sched.h"
#include "linux/slab.h"
#include "chan_kern.h"
#include "irq_kern.h"
#include "irq_user.h"
#include "kern_util.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;

	if (line)
		chan_interrupt(&line->chan_list, &line->task, line->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; /* 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;

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

	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 ==