I tried to check cat operations for tiny_tty driver from LDD book.
What is wrong with cat operation here?
Here is the output from strace cat hello > /dev/my_tty1
root@andy:/home# strace cat hello > /dev/my_tty1
execve("/bin/cat", ["cat", "hello"], [/* 12 vars */]) = 0
brk(0) = 0x7d000
open("/etc/ld.so.preload", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=5664, ...}) = 0
old_mmap(NULL, 5664, PROT_READ, MAP_PRIVATE, 3, 0) = 0x40017000
close(3) = 0
open("/lib/libm.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1a\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\250B\0\000"..., 512) = 51
2
fstat64(3, {st_mode=S_IFREG|0755, st_size=480324, ...}) = 0
old_mmap(NULL, 506412, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x40020000
mprotect(0x40093000, 35372, PROT_NONE) = 0
old_mmap(0x40098000, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x70
000) = 0x40098000
close(3) = 0
open("/lib/libcrypt.so.1", O_RDONLY) = 3
read(3, "\177ELF\1\1\1a\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\260\10\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=19940, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0
x40019000
old_mmap(NULL, 211220, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x4009c000
mprotect(0x400a1000, 190740, PROT_NONE) = 0
old_mmap(0x400a4000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0) =
0x400a4000
old_mmap(0x400a9000, 157972, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANO
NYMOUS, -1, 0) = 0x400a9000
close(3) = 0
open("/lib/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1a\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\330p\1\000"..., 512) = 51
2
fstat64(3, {st_mode=S_IFREG|0755, st_size=1240024, ...}) = 0
old_mmap(NULL, 1257088, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x400d0000
mprotect(0x401f5000, 56960, PROT_NONE) = 0
old_mmap(0x401f8000, 36864, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x12
0000) = 0x401f8000
old_mmap(0x40201000, 7808, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONY
MOUS, -1, 0) = 0x40201000
close(3) = 0
munmap(0x40017000, 5664) = 0
getuid32() = 0
getgid32() = 0
setgid32(0) = 0
setuid32(0) = 0
brk(0) = 0x7d000
brk(0x9e000) = 0x9e000
brk(0) = 0x9e000
open("hello", O_RDONLY) = 3
read(3, "123456789", 8192) = 9
write(1, "123456789", 9) = -1 EINVAL (Invalid argument)//??????????
write(2, "cat: ", 5cat: ) = 5
write(2, "Write Error", 11Write Error) = 11
write(2, ": Invalid argument\n", 19: Invalid argument
) = 19
close(3) = 0
io_submit(0, 0x40200164, 0 <unfinished ... exit status 0>
Process 1432 detached
root@andy:/home#
------------------------------------------------------------------------------------
/*
* Tiny TTY driver
*
* Copyright (C) 2002-2004 Greg Kroah-Hartman ([email protected])
*
* 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 <[email protected]>"
#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 */
((msr & MSR_CD) ? TIOCM_CAR : 0) | /* Carrier detect is set*/
((msr & MSR_RI) ? TIOCM_RI : 0) | /* Ring Indicator is set */
((msr & MSR_DSR) ? TIOCM_DSR : 0); /* DSR is set */
return result;
}
static int tiny_tiocmset(struct tty_struct *tty, struct file *file, unsigned int set, unsigned int clear)
{
struct tiny_serial *tiny = tty->driver_data;
unsigned int mcr = tiny->mcr;
if (set & TIOCM_RTS)
mcr |= MCR_RTS;
if (set & TIOCM_DTR)
mcr |= MCR_RTS;
if (clear & TIOCM_RTS)
mcr &= ~MCR_RTS;
if (clear & TIOCM_DTR)
mcr &= ~MCR_RTS;
/* set the new MCR value in the device */
tiny->mcr = mcr;
return 0;
}
static int tiny_read_proc(char *page, char **start, off_t off, int count,
int *eof, void *data)
{
struct tiny_serial *tiny;
off_t begin = 0;
int length = 0;
int i;
length += sprintf(page, "tinyserinfo:1.0 driver:%s\n", DRIVER_VERSION);
for (i = 0; i < TINY_TTY_MINORS && length < PAGE_SIZE; ++i) {
tiny = tiny_table[i];
if (tiny == NULL)
continue;
length += sprintf(page+length, "%d\n", i);
if ((length + begin) > (off + count))
goto done;
if ((length + begin) < off) {
begin += length;
length = 0;
}
}
*eof = 1;
done:
if (off >= (length + begin))
return 0;
*start = page + (off-begin);
return (count < begin+length-off) ? count : begin + length-off;
}
#define tiny_ioctl tiny_ioctl_tiocgserial
static int tiny_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg)
{
struct tiny_serial *tiny = tty->driver_data;
if (cmd == TIOCGSERIAL) {
struct serial_struct tmp;
if (!arg)
return -EFAULT;
memset(&tmp, 0, sizeof(tmp));
tmp.type = tiny->serial.type;
tmp.line = tiny->serial.line;
tmp.port = tiny->serial.port;
tmp.irq = tiny->serial.irq;
tmp.flags = ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ;
tmp.xmit_fifo_size = tiny->serial.xmit_fifo_size;
tmp.baud_base = tiny->serial.baud_base;
tmp.close_delay = 5*HZ;
tmp.closing_wait = 30*HZ;
tmp.custom_divisor = tiny->serial.custom_divisor;
tmp.hub6 = tiny->serial.hub6;
tmp.io_type = tiny->serial.io_type;
if (copy_to_user((void __user *)arg, &tmp, sizeof(struct serial_struct)))
return -EFAULT;
return 0;
}
return -ENOIOCTLCMD;
}
#undef tiny_ioctl
#define tiny_ioctl tiny_ioctl_tiocmiwait
static int tiny_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg)
{
struct tiny_serial *tiny = tty->driver_data;
if (cmd == TIOCMIWAIT) {
DECLARE_WAITQUEUE(wait, current);
struct async_icount cnow;
struct async_icount cprev;
cprev = tiny->icount;
while (1) {
add_wait_queue(&tiny->wait, &wait);
set_current_state(TASK_INTERRUPTIBLE);
schedule();
remove_wait_queue(&tiny->wait, &wait);
/* see if a signal woke us up */
if (signal_pending(current))
return -ERESTARTSYS;
cnow = tiny->icount;
if (cnow.rng == cprev.rng && cnow.dsr == cprev.dsr &&
cnow.dcd == cprev.dcd && cnow.cts == cprev.cts)
return -EIO; /* no change => error */
if (((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) ||
((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) ||
((arg & TIOCM_CD) && (cnow.dcd != cprev.dcd)) ||
((arg & TIOCM_CTS) && (cnow.cts != cprev.cts)) ) {
return 0;
}
cprev = cnow;
}
}
return -ENOIOCTLCMD;
}
#undef tiny_ioctl
#define tiny_ioctl tiny_ioctl_tiocgicount
static int tiny_ioctl(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg)
{
struct tiny_serial *tiny = tty->driver_data;
if (cmd == TIOCGICOUNT) {
struct async_icount cnow = tiny->icount;
struct serial_icounter_struct icount;
icount.cts = cnow.cts;
icount.dsr = cnow.dsr;
icount.rng = cnow.rng;
icount.dcd = cnow.dcd;
icount.rx = cnow.rx;
icount.tx = cnow.tx;
icount.frame = cnow.frame;
icount.overrun = cnow.overrun;
icount.parity = cnow.parity;
icount.brk = cnow.brk;
icount.buf_overrun = cnow.buf_overrun;
if (copy_to_user((void __user *)arg, &icount, sizeof(icount)))
return -EFAULT;
return 0;
}
return -ENOIOCTLCMD;
}
#undef tiny_ioctl
/* the real tiny_ioctl function. The above is done to get the small functions in the book */
static int tiny_ioctl(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg)
{
switch (cmd) {
case TIOCGSERIAL:
return tiny_ioctl_tiocgserial(tty, file, cmd, arg);
case TIOCMIWAIT:
return tiny_ioctl_tiocmiwait(tty, file, cmd, arg);
case TIOCGICOUNT:
return tiny_ioctl_tiocgicount(tty, file, cmd, arg);
}
return -ENOIOCTLCMD;
}
static struct tty_operations serial_ops = {
.open = tiny_open,
.close = tiny_close,
.write = tiny_write,
.write_room = tiny_write_room,
.set_termios = tiny_set_termios,
};
static struct tty_driver *tiny_tty_driver;
static int __init tiny_init(void)
{
int retval;
int i;
/* allocate the tty driver */
tiny_tty_driver = alloc_tty_driver(TINY_TTY_MINORS);
if (!tiny_tty_driver)
return -ENOMEM;
/* initialize the tty driver */
tiny_tty_driver->owner = THIS_MODULE;
tiny_tty_driver->driver_name = "tiny_tty";
tiny_tty_driver->name = "ttty";
tiny_tty_driver->devfs_name = "tts/ttty%d";
tiny_tty_driver->major = TINY_TTY_MAJOR,
tiny_tty_driver->type = TTY_DRIVER_TYPE_SERIAL,
tiny_tty_driver->subtype = SERIAL_TYPE_NORMAL,
tiny_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_NO_DEVFS,
tiny_tty_driver->init_termios = tty_std_termios;
tiny_tty_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;
tty_set_operations(tiny_tty_driver, &serial_ops);
/* hack to make the book purty, yet still use these functions in the
* real driver. They really should be set up in the serial_ops
* structure above... */
tiny_tty_driver->read_proc = tiny_read_proc;
tiny_tty_driver->tiocmget = tiny_tiocmget;
tiny_tty_driver->tiocmset = tiny_tiocmset;
tiny_tty_driver->ioctl = tiny_ioctl;
/* register the tty driver */
retval = tty_register_driver(tiny_tty_driver);
if (retval) {
printk(KERN_ERR "failed to register tiny tty driver");
put_tty_driver(tiny_tty_driver);
return retval;
}
for (i = 0; i < TINY_TTY_MINORS; ++i)
tty_register_device(tiny_tty_driver, i, NULL);
printk(KERN_INFO DRIVER_DESC " " DRIVER_VERSION);
return retval;
}
static void __exit tiny_exit(void)
{
struct tiny_serial *tiny;
int i;
for (i = 0; i < TINY_TTY_MINORS; ++i)
tty_unregister_device(tiny_tty_driver, i);
tty_unregister_driver(tiny_tty_driver);
/* shut down all of the timers and free the memory */
for (i = 0; i < TINY_TTY_MINORS; ++i) {
tiny = tiny_table[i];
if (tiny) {
/* close the port */
while (tiny->open_count)
do_close(tiny);
/* shut down our timer and free the memory */
del_timer(tiny->timer);
kfree(tiny->timer);
kfree(tiny);
tiny_table[i] = NULL;
}
}
}
module_init(tiny_init);
module_exit(tiny_exit);
--------------------------------------------------------------------------------------
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