/*
* Tiny TTY driver
*
* Copyright (C) 2002-2004 Greg Kroah-Hartman (greg@kroah.com)
*
* 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, version 2 of the License.
*
* This driver shows how to create a minimal tty driver. It does not rely on
* any backing hardware, but creates a timer that emulates data being received
* from some kind of hardware.
*/
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <asm/uaccess.h>
#define DRIVER_VERSION "v2.0"
#define DRIVER_AUTHOR "Greg Kroah-Hartman <greg@kroah.com>"
#define DRIVER_DESC "Tiny TTY driver"
/* Module information */
MODULE_AUTHOR( DRIVER_AUTHOR );
MODULE_DESCRIPTION( DRIVER_DESC );
MODULE_LICENSE("GPL");
#define DELAY_TIME HZ * 2 /* 2 seconds per character */
#define TINY_DATA_CHARACTER 't'
#define TINY_TTY_MAJOR 240 /* experimental range */
#define TINY_TTY_MINORS 4 /* only have 4 devices */
struct tiny_serial {
struct tty_struct *tty; /* pointer to the tty for this device */
int open_count; /* number of times this port has been opened */
struct semaphore sem; /* locks this structure */
struct timer_list *timer;
/* for tiocmget and tiocmset functions */
int msr; /* MSR shadow */
int mcr; /* MCR shadow */
/* for ioctl fun */
struct serial_struct serial;
wait_queue_head_t wait;
struct async_icount icount;
};
static struct tiny_serial *tiny_table[TINY_TTY_MINORS]; /* initially all NULL */
static void tiny_timer(unsigned long timer_data)
{
struct tiny_serial *tiny = (struct tiny_serial *)timer_data;
struct tty_struct *tty;
int i;
char data[1] = {TINY_DATA_CHARACTER};
int data_size = 1;
if (!tiny)
return;
tty = tiny->tty;
/* send the data to the tty layer for users to read. This doesn't
* actually push the data through unless tty->low_latency is set */
for (i = 0; i < data_size; ++i) {
if (tty->flip.count >= TTY_FLIPBUF_SIZE)
tty_flip_buffer_push(tty);
tty_insert_flip_char(tty, data[i], TTY_NORMAL);
}
tty_flip_buffer_push(tty);
/* resubmit the timer again */
tiny->timer->expires = jiffies + DELAY_TIME;
add_timer(tiny->timer);
}
static int tiny_open(struct tty_struct *tty, struct file *file)
{
struct tiny_serial *tiny;
struct timer_list *timer;
int index;
/* initialize the pointer in case something fails */
tty->driver_data = NULL;
/* get the serial object associated with this tty pointer */
index = tty->index;
tiny = tiny_table[index];
if (tiny == NULL) {
/* first time accessing this device, let's create it */
tiny = kmalloc(sizeof(*tiny), GFP_KERNEL);
if (!tiny)
return -ENOMEM;
init_MUTEX(&tiny->sem);
tiny->open_count = 0;
tiny->timer = NULL;
tiny_table[index] = tiny;
}
down(&tiny->sem);
/* save our structure within the tty structure */
tty->driver_data = tiny;
tiny->tty = tty;
++tiny->open_count;
if (tiny->open_count == 1) {
/* this is the first time this port is opened */
/* do any hardware initialization needed here */
/* create our timer and submit it */
if (!tiny->timer) {
timer = kmalloc(sizeof(*timer), GFP_KERNEL);
if (!timer) {
up(&tiny->sem);
return -ENOMEM;
}
tiny->timer = timer;
}
tiny->timer->data = (unsigned long )tiny;
tiny->timer->expires = jiffies + DELAY_TIME;
tiny->timer->function = tiny_timer;
add_timer(tiny->timer);
}
up(&tiny->sem);
return 0;
}
static void do_close(struct tiny_serial *tiny)
{
down(&tiny->sem);
if (!tiny->open_count) {
/* port was never opened */
goto exit;
}
--tiny->open_count;
if (tiny->open_count <= 0) {
/* The port is being closed by the last user. */
/* Do any hardware specific stuff here */
/* shut down our timer */
del_timer(tiny->timer);
}
exit:
up(&tiny->sem);
}
static void tiny_close(struct tty_struct *tty, struct file *file)
{
struct tiny_serial *tiny = tty->driver_data;
if (tiny)
do_close(tiny);
}
static int tiny_write(struct tty_struct *tty,
const unsigned char *buffer, int count)
{
struct tiny_serial *tiny = tty->driver_data;
int i;
int retval = -EINVAL;
if (!tiny)
return -ENODEV;
down(&tiny->sem);
if (!tiny->open_count)
/* port was not opened */
goto exit;
/* fake sending the data out a hardware port by
* writing it to the kernel debug log.
*/
printk(KERN_DEBUG "%s - ", __FUNCTION__);
for (i = 0; i < count; ++i)
printk("%02x ", buffer[i]);
printk("\n");
exit:
up(&tiny->sem);
return retval;
}
static int tiny_write_room(struct tty_struct *tty)
{
struct tiny_serial *tiny = tty->driver_data;
int room = -EINVAL;
if (!tiny)
return -ENODEV;
down(&tiny->sem);
if (!tiny->open_count) {
/* port was not opened */
goto exit;
}
/* calculate how much room is left in the device */
room = 255;
exit:
up(&tiny->sem);
return room;
}
#define RELEVANT_IFLAG(iflag) ((iflag) & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))
static void tiny_set_termios(struct tty_struct *tty, struct termios *old_termios)
{
unsigned int cflag;
cflag = tty->termios->c_cflag;
/* check that they really want us to change something */
if (old_termios) {
if ((cflag == old_termios->c_cflag) &&
(RELEVANT_IFLAG(tty->termios->c_iflag) ==
RELEVANT_IFLAG(old_termios->c_iflag))) {
printk(KERN_DEBUG " - nothing to change...\n");
return;
}
}
/* get the byte size */
switch (cflag & CSIZE) {
case CS5:
printk(KERN_DEBUG " - data bits = 5\n");
break;
case CS6:
printk(KERN_DEBUG " - data bits = 6\n");
break;
case CS7:
printk(KERN_DEBUG " - data bits = 7\n");
break;
default:
case CS8:
printk(KERN_DEBUG " - data bits = 8\n");
break;
}
/* determine the parity */
if (cflag & PARENB)
if (cflag & PARODD)
printk(KERN_DEBUG " - parity = odd\n");
else
printk(KERN_DEBUG " - parity = even\n");
else
printk(KERN_DEBUG " - parity = none\n");
/* figure out the stop bits requested */
if (cflag & CSTOPB)
printk(KERN_DEBUG " - stop bits = 2\n");
else
printk(KERN_DEBUG " - stop bits = 1\n");
/* figure out the hardware flow control settings */
if (cflag & CRTSCTS)
printk(KERN_DEBUG " - RTS/CTS is enabled\n");
else
printk(KERN_DEBUG " - RTS/CTS is disabled\n");
/* determine software flow control */
/* if we are implementing XON/XOFF, set the start and
* stop character in the device */
if (I_IXOFF(tty) || I_IXON(tty)) {
unsigned char stop_char = STOP_CHAR(tty);
unsigned char start_char = START_CHAR(tty);
/* if we are implementing INBOUND XON/XOFF */
if (I_IXOFF(tty))
printk(KERN_DEBUG " - INBOUND XON/XOFF is enabled, "
"XON = %2x, XOFF = %2x", start_char, stop_char);
else
printk(KERN_DEBUG" - INBOUND XON/XOFF is disabled");
/* if we are implementing OUTBOUND XON/XOFF */
if (I_IXON(tty))
printk(KERN_DEBUG" - OUTBOUND XON/XOFF is enabled, "
"XON = %2x, XOFF = %2x", start_char, stop_char);
else
printk(KERN_DEBUG" - OUTBOUND XON/XOFF is disabled");
}
/* get the baud rate wanted */
printk(KERN_DEBUG " - baud rate = %d", tty_get_baud_rate(tty));
}
/* Our fake UART values */
#define MCR_DTR 0x01
#define MCR_RTS 0x02
#define MCR_LOOP 0x04
#define MSR_CTS 0x08
#define MSR_CD 0x10
#define MSR_RI 0x20
#define MSR_DSR 0x40
static int tiny_tiocmget(struct tty_struct *tty, struct file *file)
{
struct tiny_serial *tiny = tty->driver_data;
unsigned int result = 0;
unsigned int msr = tiny->msr;
unsigned int mcr = tiny->mcr;
result = ((mcr & MCR_DTR) ? TIOCM_DTR : 0) | /* DTR is set */
((mcr & MCR_RTS) ? TIOCM_RTS : 0) | /* RTS is set */
((mcr & MCR_LOOP) ? TIOCM_LOOP : 0) | /* LOOP is set */
((msr & MSR_CTS) ? TIOCM_CTS : 0) | /* CTS is set
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