drivers/char/dcc_tty.c - kernel/panda - Git at Google

 /* drivers/char/dcc_tty.c
  *
  * Copyright (C) 2007 Google, Inc.
  *
  * This software is licensed under the terms of the GNU General Public
  * License version 2, as published by the Free Software Foundation, and
  * may be copied, distributed, and modified under those terms.
  *
  * 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.
  *
  */

 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/delay.h>
 #include <linux/console.h>
 #include <linux/hrtimer.h>
 #include <linux/tty.h>
 #include <linux/tty_driver.h>
 #include <linux/tty_flip.h>

 MODULE_DESCRIPTION("DCC TTY Driver");
 MODULE_LICENSE("GPL");
 MODULE_VERSION("1.0");

 static DEFINE_SPINLOCK(g_dcc_tty_lock);
 static struct hrtimer g_dcc_timer;
 static char g_dcc_buffer[16];
 static int g_dcc_buffer_head;
 static int g_dcc_buffer_count;
 static unsigned g_dcc_write_delay_usecs = 1;
 static struct tty_driver *g_dcc_tty_driver;
 static struct tty_struct *g_dcc_tty;
 static int g_dcc_tty_open_count;

 static void dcc_poll_locked(void)
 {
 	char ch;
 	int rch;
 	int written;

 	while (g_dcc_buffer_count) {
 		ch = g_dcc_buffer[g_dcc_buffer_head];
 		asm(
 			"mrc 14, 0, r15, c0, c1, 0\n"
 			"mcrcc 14, 0, %1, c0, c5, 0\n"
 			"movcc %0, #1\n"
 			"movcs %0, #0\n"
 			: "=r" (written)
 			: "r" (ch)
 		);
 		if (written) {
 			if (ch == '\n')
 				g_dcc_buffer[g_dcc_buffer_head] = '\r';
 			else {
 				g_dcc_buffer_head = (g_dcc_buffer_head + 1) % ARRAY_SIZE(g_dcc_buffer);
 				g_dcc_buffer_count--;
 				if (g_dcc_tty)
 					tty_wakeup(g_dcc_tty);
 			}
 			g_dcc_write_delay_usecs = 1;
 		} else {
 			if (g_dcc_write_delay_usecs > 0x100)
 				break;
 			g_dcc_write_delay_usecs <<= 1;
 			udelay(g_dcc_write_delay_usecs);
 		}
 	}

 	if (g_dcc_tty && !test_bit(TTY_THROTTLED, &g_dcc_tty->flags)) {
 		asm(
 			"mrc 14, 0, %0, c0, c1, 0\n"
 			"tst %0, #(1 << 30)\n"
 			"moveq %0, #-1\n"
 			"mrcne 14, 0, %0, c0, c5, 0\n"
 			: "=r" (rch)
 		);
 		if (rch >= 0) {
 			ch = rch;
 			tty_insert_flip_string(g_dcc_tty, &ch, 1);
 			tty_flip_buffer_push(g_dcc_tty);
 		}
 	}


 	if (g_dcc_buffer_count)
 		hrtimer_start(&g_dcc_timer, ktime_set(0, g_dcc_write_delay_usecs * NSEC_PER_USEC), HRTIMER_MODE_REL);
 	else
 		hrtimer_start(&g_dcc_timer, ktime_set(0, 20 * NSEC_PER_MSEC), HRTIMER_MODE_REL);
 }

 static int dcc_tty_open(struct tty_struct * tty, struct file * filp)
 {
 	int ret;
 	unsigned long irq_flags;

 	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
 	if (g_dcc_tty == NULL || g_dcc_tty == tty) {
 		g_dcc_tty = tty;
 		g_dcc_tty_open_count++;
 		ret = 0;
 	} else
 		ret = -EBUSY;
 	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);

 	printk("dcc_tty_open, tty %p, f_flags %x, returned %d\n", tty, filp->f_flags, ret);

 	return ret;
 }

 static void dcc_tty_close(struct tty_struct * tty, struct file * filp)
 {
 	printk("dcc_tty_close, tty %p, f_flags %x\n", tty, filp->f_flags);
 	if (g_dcc_tty == tty) {
 		if (--g_dcc_tty_open_count == 0)
 			g_dcc_tty = NULL;
 	}
 }

 static int dcc_write(const unsigned char *buf_start, int count)
 {
 	const unsigned char *buf = buf_start;
 	unsigned long irq_flags;
 	int copy_len;
 	int space_left;
 	int tail;

 	if (count < 1)
 		return 0;

 	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
 	do {
 		tail = (g_dcc_buffer_head + g_dcc_buffer_count) % ARRAY_SIZE(g_dcc_buffer);
 		copy_len = ARRAY_SIZE(g_dcc_buffer) - tail;
 		space_left = ARRAY_SIZE(g_dcc_buffer) - g_dcc_buffer_count;
 		if (copy_len > space_left)
 			copy_len = space_left;
 		if (copy_len > count)
 			copy_len = count;
 		memcpy(&g_dcc_buffer[tail], buf, copy_len);
 		g_dcc_buffer_count += copy_len;
 		buf += copy_len;
 		count -= copy_len;
 		if (copy_len < count && copy_len < space_left) {
 			space_left -= copy_len;
 			copy_len = count;
 			if (copy_len > space_left) {
 				copy_len = space_left;
 			}
 			memcpy(g_dcc_buffer, buf, copy_len);
 			buf += copy_len;
 			count -= copy_len;
 			g_dcc_buffer_count += copy_len;
 		}
 		dcc_poll_locked();
 		space_left = ARRAY_SIZE(g_dcc_buffer) - g_dcc_buffer_count;
 	} while(count && space_left);
 	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
 	return buf - buf_start;
 }

 static int dcc_tty_write(struct tty_struct * tty, const unsigned char *buf, int count)
 {
 	int ret;
 	/* printk("dcc_tty_write %p, %d\n", buf, count); */
 	ret = dcc_write(buf, count);
 	if (ret != count)
 		printk("dcc_tty_write %p, %d, returned %d\n", buf, count, ret);
 	return ret;
 }

 static int dcc_tty_write_room(struct tty_struct *tty)
 {
 	int space_left;
 	unsigned long irq_flags;

 	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
 	space_left = ARRAY_SIZE(g_dcc_buffer) - g_dcc_buffer_count;
 	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
 	return space_left;
 }

 static int dcc_tty_chars_in_buffer(struct tty_struct *tty)
 {
 	int ret;
 	asm(
 		"mrc 14, 0, %0, c0, c1, 0\n"
 		"mov %0, %0, LSR #30\n"
 		"and %0, %0, #1\n"
 		: "=r" (ret)
 	);
 	return ret;
 }

 static void dcc_tty_unthrottle(struct tty_struct * tty)
 {
 	unsigned long irq_flags;

 	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
 	dcc_poll_locked();
 	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
 }

 static enum hrtimer_restart dcc_tty_timer_func(struct hrtimer *timer)
 {
 	unsigned long irq_flags;

 	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
 	dcc_poll_locked();
 	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
 	return HRTIMER_NORESTART;
 }

 void dcc_console_write(struct console *co, const char *b, unsigned count)
 {
 #if 1
 	dcc_write(b, count);
 #else
 	/* blocking printk */
 	while (count > 0) {
 		int written;
 		written = dcc_write(b, count);
 		if (written) {
 			b += written;
 			count -= written;
 		}
 	}
 #endif
 }

 static struct tty_driver *dcc_console_device(struct console *c, int *index)
 {
 	*index = 0;
 	return g_dcc_tty_driver;
 }

 static int __init dcc_console_setup(struct console *co, char *options)
 {
 	if (co->index != 0)
 		return -ENODEV;
 	return 0;
 }


 static struct console dcc_console =
 {
 	.name		= "ttyDCC",
 	.write		= dcc_console_write,
 	.device		= dcc_console_device,
 	.setup		= dcc_console_setup,
 	.flags		= CON_PRINTBUFFER,
 	.index		= -1,
 };

 static struct tty_operations dcc_tty_ops = {
 	.open = dcc_tty_open,
 	.close = dcc_tty_close,
 	.write = dcc_tty_write,
 	.write_room = dcc_tty_write_room,
 	.chars_in_buffer = dcc_tty_chars_in_buffer,
 	.unthrottle = dcc_tty_unthrottle,
 };

 static int __init dcc_tty_init(void)
 {
 	int ret;

 	hrtimer_init(&g_dcc_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	g_dcc_timer.function = dcc_tty_timer_func;

 	g_dcc_tty_driver = alloc_tty_driver(1);
 	if (!g_dcc_tty_driver) {
 		printk(KERN_ERR "dcc_tty_probe: alloc_tty_driver failed\n");
 		ret = -ENOMEM;
 		goto err_alloc_tty_driver_failed;
 	}
 	g_dcc_tty_driver->owner = THIS_MODULE;
 	g_dcc_tty_driver->driver_name = "dcc";
 	g_dcc_tty_driver->name = "ttyDCC";
 	g_dcc_tty_driver->major = 0; // auto assign
 	g_dcc_tty_driver->minor_start = 0;
 	g_dcc_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
 	g_dcc_tty_driver->subtype = SERIAL_TYPE_NORMAL;
 	g_dcc_tty_driver->init_termios = tty_std_termios;
 	g_dcc_tty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
 	tty_set_operations(g_dcc_tty_driver, &dcc_tty_ops);
 	ret = tty_register_driver(g_dcc_tty_driver);
 	if (ret) {
 		printk(KERN_ERR "dcc_tty_probe: tty_register_driver failed, %d\n", ret);
 		goto err_tty_register_driver_failed;
 	}
 	tty_register_device(g_dcc_tty_driver, 0, NULL);

 	register_console(&dcc_console);
 	hrtimer_start(&g_dcc_timer, ktime_set(0, 0), HRTIMER_MODE_REL);

 	return 0;

 err_tty_register_driver_failed:
 	put_tty_driver(g_dcc_tty_driver);
 	g_dcc_tty_driver = NULL;
 err_alloc_tty_driver_failed:
 	return ret;
 }

 static void  __exit dcc_tty_exit(void)
 {
 	int ret;

 	tty_unregister_device(g_dcc_tty_driver, 0);
 	ret = tty_unregister_driver(g_dcc_tty_driver);
 	if (ret < 0) {
 		printk(KERN_ERR "dcc_tty_remove: tty_unregister_driver failed, %d\n", ret);
 	} else {
 		put_tty_driver(g_dcc_tty_driver);
 	}
 	g_dcc_tty_driver = NULL;
 }

 module_init(dcc_tty_init);
 module_exit(dcc_tty_exit);
	/* drivers/char/dcc_tty.c
	*
	* Copyright (C) 2007 Google, Inc.
	*
	* This software is licensed under the terms of the GNU General Public
	* License version 2, as published by the Free Software Foundation, and
	* may be copied, distributed, and modified under those terms.
	*
	* 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.
	*
	*/

	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/delay.h>
	#include <linux/console.h>
	#include <linux/hrtimer.h>
	#include <linux/tty.h>
	#include <linux/tty_driver.h>
	#include <linux/tty_flip.h>

	MODULE_DESCRIPTION("DCC TTY Driver");
	MODULE_LICENSE("GPL");
	MODULE_VERSION("1.0");

	static DEFINE_SPINLOCK(g_dcc_tty_lock);
	static struct hrtimer g_dcc_timer;
	static char g_dcc_buffer[16];
	static int g_dcc_buffer_head;
	static int g_dcc_buffer_count;
	static unsigned g_dcc_write_delay_usecs = 1;
	static struct tty_driver *g_dcc_tty_driver;
	static struct tty_struct *g_dcc_tty;
	static int g_dcc_tty_open_count;

	static void dcc_poll_locked(void)
	{
	char ch;
	int rch;
	int written;

	while (g_dcc_buffer_count) {
	ch = g_dcc_buffer[g_dcc_buffer_head];
	asm(
	"mrc 14, 0, r15, c0, c1, 0\n"
	"mcrcc 14, 0, %1, c0, c5, 0\n"
	"movcc %0, #1\n"
	"movcs %0, #0\n"
	: "=r" (written)
	: "r" (ch)
	);
	if (written) {
	if (ch == '\n')
	g_dcc_buffer[g_dcc_buffer_head] = '\r';
	else {
	g_dcc_buffer_head = (g_dcc_buffer_head + 1) % ARRAY_SIZE(g_dcc_buffer);
	g_dcc_buffer_count--;
	if (g_dcc_tty)
	tty_wakeup(g_dcc_tty);
	}
	g_dcc_write_delay_usecs = 1;
	} else {
	if (g_dcc_write_delay_usecs > 0x100)
	break;
	g_dcc_write_delay_usecs <<= 1;
	udelay(g_dcc_write_delay_usecs);
	}
	}

	if (g_dcc_tty && !test_bit(TTY_THROTTLED, &g_dcc_tty->flags)) {
	asm(
	"mrc 14, 0, %0, c0, c1, 0\n"
	"tst %0, #(1 << 30)\n"
	"moveq %0, #-1\n"
	"mrcne 14, 0, %0, c0, c5, 0\n"
	: "=r" (rch)
	);
	if (rch >= 0) {
	ch = rch;
	tty_insert_flip_string(g_dcc_tty, &ch, 1);
	tty_flip_buffer_push(g_dcc_tty);
	}
	}


	if (g_dcc_buffer_count)
	hrtimer_start(&g_dcc_timer, ktime_set(0, g_dcc_write_delay_usecs * NSEC_PER_USEC), HRTIMER_MODE_REL);
	else
	hrtimer_start(&g_dcc_timer, ktime_set(0, 20 * NSEC_PER_MSEC), HRTIMER_MODE_REL);
	}

	static int dcc_tty_open(struct tty_struct * tty, struct file * filp)
	{
	int ret;
	unsigned long irq_flags;

	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
	if (g_dcc_tty == NULL \|\| g_dcc_tty == tty) {
	g_dcc_tty = tty;
	g_dcc_tty_open_count++;
	ret = 0;
	} else
	ret = -EBUSY;
	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);

	printk("dcc_tty_open, tty %p, f_flags %x, returned %d\n", tty, filp->f_flags, ret);

	return ret;
	}

	static void dcc_tty_close(struct tty_struct * tty, struct file * filp)
	{
	printk("dcc_tty_close, tty %p, f_flags %x\n", tty, filp->f_flags);
	if (g_dcc_tty == tty) {
	if (--g_dcc_tty_open_count == 0)
	g_dcc_tty = NULL;
	}
	}

	static int dcc_write(const unsigned char *buf_start, int count)
	{
	const unsigned char *buf = buf_start;
	unsigned long irq_flags;
	int copy_len;
	int space_left;
	int tail;

	if (count < 1)
	return 0;

	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
	do {
	tail = (g_dcc_buffer_head + g_dcc_buffer_count) % ARRAY_SIZE(g_dcc_buffer);
	copy_len = ARRAY_SIZE(g_dcc_buffer) - tail;
	space_left = ARRAY_SIZE(g_dcc_buffer) - g_dcc_buffer_count;
	if (copy_len > space_left)
	copy_len = space_left;
	if (copy_len > count)
	copy_len = count;
	memcpy(&g_dcc_buffer[tail], buf, copy_len);
	g_dcc_buffer_count += copy_len;
	buf += copy_len;
	count -= copy_len;
	if (copy_len < count && copy_len < space_left) {
	space_left -= copy_len;
	copy_len = count;
	if (copy_len > space_left) {
	copy_len = space_left;
	}
	memcpy(g_dcc_buffer, buf, copy_len);
	buf += copy_len;
	count -= copy_len;
	g_dcc_buffer_count += copy_len;
	}
	dcc_poll_locked();
	space_left = ARRAY_SIZE(g_dcc_buffer) - g_dcc_buffer_count;
	} while(count && space_left);
	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
	return buf - buf_start;
	}

	static int dcc_tty_write(struct tty_struct * tty, const unsigned char *buf, int count)
	{
	int ret;
	/* printk("dcc_tty_write %p, %d\n", buf, count); */
	ret = dcc_write(buf, count);
	if (ret != count)
	printk("dcc_tty_write %p, %d, returned %d\n", buf, count, ret);
	return ret;
	}

	static int dcc_tty_write_room(struct tty_struct *tty)
	{
	int space_left;
	unsigned long irq_flags;

	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
	space_left = ARRAY_SIZE(g_dcc_buffer) - g_dcc_buffer_count;
	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
	return space_left;
	}

	static int dcc_tty_chars_in_buffer(struct tty_struct *tty)
	{
	int ret;
	asm(
	"mrc 14, 0, %0, c0, c1, 0\n"
	"mov %0, %0, LSR #30\n"
	"and %0, %0, #1\n"
	: "=r" (ret)
	);
	return ret;
	}

	static void dcc_tty_unthrottle(struct tty_struct * tty)
	{
	unsigned long irq_flags;

	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
	dcc_poll_locked();
	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
	}

	static enum hrtimer_restart dcc_tty_timer_func(struct hrtimer *timer)
	{
	unsigned long irq_flags;

	spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
	dcc_poll_locked();
	spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
	return HRTIMER_NORESTART;
	}

	void dcc_console_write(struct console co, const char b, unsigned count)
	{
	#if 1
	dcc_write(b, count);
	#else
	/* blocking printk */
	while (count > 0) {
	int written;
	written = dcc_write(b, count);
	if (written) {
	b += written;
	count -= written;
	}
	}
	#endif
	}

	static struct tty_driver dcc_console_device(struct console c, int *index)
	{
	*index = 0;
	return g_dcc_tty_driver;
	}

	static int __init dcc_console_setup(struct console co, char options)
	{
	if (co->index != 0)
	return -ENODEV;
	return 0;
	}


	static struct console dcc_console =
	{
	.name = "ttyDCC",
	.write = dcc_console_write,
	.device = dcc_console_device,
	.setup = dcc_console_setup,
	.flags = CON_PRINTBUFFER,
	.index = -1,
	};

	static struct tty_operations dcc_tty_ops = {
	.open = dcc_tty_open,
	.close = dcc_tty_close,
	.write = dcc_tty_write,
	.write_room = dcc_tty_write_room,
	.chars_in_buffer = dcc_tty_chars_in_buffer,
	.unthrottle = dcc_tty_unthrottle,
	};

	static int __init dcc_tty_init(void)
	{
	int ret;

	hrtimer_init(&g_dcc_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	g_dcc_timer.function = dcc_tty_timer_func;

	g_dcc_tty_driver = alloc_tty_driver(1);
	if (!g_dcc_tty_driver) {
	printk(KERN_ERR "dcc_tty_probe: alloc_tty_driver failed\n");
	ret = -ENOMEM;
	goto err_alloc_tty_driver_failed;
	}
	g_dcc_tty_driver->owner = THIS_MODULE;
	g_dcc_tty_driver->driver_name = "dcc";
	g_dcc_tty_driver->name = "ttyDCC";
	g_dcc_tty_driver->major = 0; // auto assign
	g_dcc_tty_driver->minor_start = 0;
	g_dcc_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
	g_dcc_tty_driver->subtype = SERIAL_TYPE_NORMAL;
	g_dcc_tty_driver->init_termios = tty_std_termios;
	g_dcc_tty_driver->flags = TTY_DRIVER_RESET_TERMIOS \| TTY_DRIVER_REAL_RAW \| TTY_DRIVER_DYNAMIC_DEV;
	tty_set_operations(g_dcc_tty_driver, &dcc_tty_ops);
	ret = tty_register_driver(g_dcc_tty_driver);
	if (ret) {
	printk(KERN_ERR "dcc_tty_probe: tty_register_driver failed, %d\n", ret);
	goto err_tty_register_driver_failed;
	}
	tty_register_device(g_dcc_tty_driver, 0, NULL);

	register_console(&dcc_console);
	hrtimer_start(&g_dcc_timer, ktime_set(0, 0), HRTIMER_MODE_REL);

	return 0;

	err_tty_register_driver_failed:
	put_tty_driver(g_dcc_tty_driver);
	g_dcc_tty_driver = NULL;
	err_alloc_tty_driver_failed:
	return ret;
	}

	static void __exit dcc_tty_exit(void)
	{
	int ret;

	tty_unregister_device(g_dcc_tty_driver, 0);
	ret = tty_unregister_driver(g_dcc_tty_driver);
	if (ret < 0) {
	printk(KERN_ERR "dcc_tty_remove: tty_unregister_driver failed, %d\n", ret);
	} else {
	put_tty_driver(g_dcc_tty_driver);
	}
	g_dcc_tty_driver = NULL;
	}

	module_init(dcc_tty_init);
	module_exit(dcc_tty_exit);