Hello,
I am writing a serial driver, and so I started investigating the
tiny_serial driver from the third edition of "Linux Device Drivers."
Original source is at the bottom of the email. When I exercise this
module using stty, EIO is returned. This also happens for reads and
writes. I am running 2.6.22 PREEMPT on Powerpc. Any help would be
greatly appreciated.
~ $ mknod /dev/ttty1 c 240 1
~ $ insmod tiny_serial.ko
~ $ stty -a -F /dev/ttty1
stty: /dev/ttty1: Input/output error
~ $ strace stty -a -F /dev/ttty1
execve("/bin/stty", ["stty", "-a", "-F", "/dev/ttty1"], [/* 7 vars */])
= 0
uname({sys="Linux", node="10.100.10.83", ...}) = 0
brk(0) = 0x1018a000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
= 0x30018000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or
directory)
open("/etc/ld.so.cache", O_RDONLY) = -1 ENOENT (No such file or
directory)
open("/lib/tls/ppc603/libcrypt.so.1", O_RDONLY) = -1 ENOENT (No such
file or directory)
stat64("/lib/tls/ppc603", 0x7ffff1e0) = -1 ENOENT (No such file or
directory)
open("/lib/tls/libcrypt.so.1", O_RDONLY) = -1 ENOENT (No such file or
directory)
stat64("/lib/tls", 0x7ffff1e0) = -1 ENOENT (No such file or
directory)
open("/lib/ppc603/libcrypt.so.1", O_RDONLY) = -1 ENOENT (No such file or
directory)
stat64("/lib/ppc603", 0x7ffff1e0) = -1 ENOENT (No such file or
directory)
open("/lib/libcrypt.so.1", O_RDONLY) = 3
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0\0\f"...,
512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=31414, ...}) = 0
mmap(0xffb4000, 245516, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE,
3, 0) = 0xffb4000
mprotect(0xffb9000, 225036, PROT_NONE) = 0
mmap(0xffc8000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x4000) = 0xffc8000
mmap(0xffc9000, 159500, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xffc9000
close(3) = 0
open("/lib/libm.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0\0\242"...,
512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=566328, ...}) = 0
mmap(0xff1b000, 559164, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE,
3, 0) = 0xff1b000
mprotect(0xff91000, 75836, PROT_NONE) = 0
mmap(0xffa1000, 12288, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x76000) = 0xffa1000
close(3) = 0
open("/lib/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0\1\316"...,
512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1531392, ...}) = 0
mmap(0xfdc6000, 1329164, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE,
3, 0) = 0xfdc6000
mprotect(0xfeef000, 112652, PROT_NONE) = 0
mmap(0xfefe000, 40960, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x128000) = 0xfefe000
mmap(0xff08000, 10252, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xff08000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
= 0x30019000
stat64("/etc/busybox.conf", 0x7ffffb30) = -1 ENOENT (No such file or
directory)
getuid() = 0
getgid() = 0
setgid(0) = 0
setuid(0) = 0
close(0) = 0
open("/dev/ttty1", O_RDONLY|O_NONBLOCK|O_LARGEFILE) = 0
fcntl64(0, F_GETFL) = 0x800 (flags
O_RDONLY|O_NONBLOCK)
fcntl64(0, F_SETFL, O_RDONLY) = 0
ioctl(0, TCGETS, 0x7ffff8e0) = -1 EIO (Input/output error)
write(2, "stty: ", 6stty: ) = 6
write(2, "/dev/ttty1", 10/dev/ttty1) = 10
write(2, ": Input/output error\n", 21: Input/output error
) = 21
exit_group(1) = ?
Process 213 detached
Full source below, apologies for mailer whitespace-damage
/*
* Tiny Serial driver
*
* Copyright (C) 2002-2004 Greg Kroah-Hartman (greg@xxxxxxxxx)
*
* 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 serial 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/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/serial_core.h>
#include <linux/module.h>
#define DRIVER_AUTHOR "Greg Kroah-Hartman <greg@xxxxxxxxx>"
#define DRIVER_DESC "Tiny serial 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_SERIAL_MAJOR 240 /* experimental range */
#define TINY_SERIAL_MINORS 1 /* only have one minor */
#define UART_NR 1 /* only use one port */
#define TINY_SERIAL_NAME "ttytiny"
#define MY_NAME TINY_SERIAL_NAME
static struct timer_list *timer;
static void tiny_stop_tx(struct uart_port *port, unsigned int tty_stop)
{
}
static void tiny_stop_rx(struct uart_port *port)
{
}
static void tiny_enable_ms(struct uart_port *port)
{
}
static void tiny_tx_chars(struct uart_port *port)
{
struct circ_buf *xmit = &port->info->xmit;
int count;
if (port->x_char) {
pr_debug("wrote %2x", port->x_char);
port->icount.tx++;
port->x_char = 0;
return;
}
if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
tiny_stop_tx(port, 0);
return;
}
count = port->fifosize >> 1;
do {
pr_debug("wrote %2x", xmit->buf[xmit->tail]);
xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
port->icount.tx++;
if (uart_circ_empty(xmit))
break;
} while (--count > 0);
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(port);
if (uart_circ_empty(xmit))
tiny_stop_tx(port, 0);
}
static void tiny_start_tx(struct uart_port *port, unsigned int
tty_start)
{
}
static void tiny_timer(unsigned long data)
{
struct uart_port *port;
struct tty_struct *tty;
port = (struct uart_port *)data;
if (!port)
return;
if (!port->info)
return;
tty = port->info->tty;
if (!tty)
return;
/* add one character to the tty port */
/* this doesn't actually push the data through unless tty->low_latency
is set /
tty_insert_flip_char(tty, TINY_DATA_CHARACTER, 0);
tty_flip_buffer_push(tty);
/* resubmit the timer again */
timer->expires = jiffies + DELAY_TIME;
add_timer(timer);
/* see if we have any data to transmit */
tiny_tx_chars(port);
}
static unsigned int tiny_tx_empty(struct uart_port *port)
{
return 0;
}
static unsigned int tiny_get_mctrl(struct uart_port *port)
{
return 0;
}
static void tiny_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
}
static void tiny_break_ctl(struct uart_port *port, int break_state)
{
}
static void tiny_set_termios(struct uart_port *port,
struct termios *new, struct termios *old)
{
int baud, quot, cflag = new->c_cflag;
/* 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: // CS8
printk(KERN_DEBUG " - data bits = 8\n");
break;
}
/* determine the parity */
if (cflag & PARENB)
if (cflag & PARODD)
pr_debug(" - parity = odd\n");
else
pr_debug(" - parity = even\n");
else
pr_debug(" - parity = none\n");
/* figure out the stop bits requested */
if (cflag & CSTOPB)
pr_debug(" - stop bits = 2\n");
else
pr_debug(" - stop bits = 1\n");
/* figure out the flow control settings */
if (cflag & CRTSCTS)
pr_debug(" - RTS/CTS is enabled\n");
else
pr_debug(" - RTS/CTS is disabled\n");
/* Set baud rate */
baud = uart_get_baud_rate(port, new, old, 0, port->uartclk/16);
quot = uart_get_divisor(port, baud);
//UART_PUT_DIV_LO(port, (quot & 0xff));
//UART_PUT_DIV_HI(port, ((quot & 0xf00) >> 8));
}
static int tiny_startup(struct uart_port *port)
{
/* this is the first time this port is opened */
/* do any hardware initialization needed here */
/* create our timer and submit it */
if (!timer) {
timer = kmalloc(sizeof(*timer), GFP_KERNEL);
if (!timer)
return -ENOMEM;
}
timer->data = (unsigned long)port;
timer->expires = jiffies + DELAY_TIME;
timer->function = tiny_timer;
add_timer(timer);
return 0;
}
static void tiny_shutdown(struct uart_port *port)
{
/* The port is being closed by the last user. */
/* Do any hardware specific stuff here */
/* shut down our timer */
del_timer(timer);
}
static const char *tiny_type(struct uart_port *port)
{
return "tinytty";
}
static void tiny_release_port(struct uart_port *port)
{
}
static int tiny_request_port(struct uart_port *port)
{
return 0;
}
static void tiny_config_port(struct uart_port *port, int flags)
{
}
static int tiny_verify_port(struct uart_port *port, struct serial_struct
*ser)
{
return 0;
}
static struct uart_ops tiny_ops = {
.tx_empty = tiny_tx_empty,
.set_mctrl = tiny_set_mctrl,
.get_mctrl = tiny_get_mctrl,
.stop_tx = tiny_stop_tx,
.start_tx = tiny_start_tx,
.stop_rx = tiny_stop_rx,
.enable_ms = tiny_enable_ms,
.break_ctl = tiny_break_ctl,
.startup = tiny_startup,
.shutdown = tiny_shutdown,
.set_termios = tiny_set_termios,
.type = tiny_type,
.release_port = tiny_release_port,
.request_port = tiny_request_port,
.config_port = tiny_config_port,
.verify_port = tiny_verify_port,
};
static struct uart_port tiny_port = {
.ops = &tiny_ops,
};
static struct uart_driver tiny_reg = {
.owner = THIS_MODULE,
.driver_name = TINY_SERIAL_NAME,
.dev_name = TINY_SERIAL_NAME,
.major = TINY_SERIAL_MAJOR,
.minor = TINY_SERIAL_MINORS,
.nr = UART_NR,
};
static int __init tiny_init(void)
{
int result;
printk(KERN_INFO "Tiny serial driver loaded\n");
result = uart_register_driver(&tiny_reg);
if (result)
return result;
result = uart_add_one_port(&tiny_reg, &tiny_port);
if (result)
uart_unregister_driver(&tiny_reg);
return result;
}
module_init(tiny_init);
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