[SOLVED] Coding an Interrupt Service Routine for the serial port in Linux !!

Aquarius_Girl · 10-21-2009, 10:48 PM

I got a problem with the following interrupt handler code with respect to serial port 1. I have a cable connecting two serial ports of two computers with linux on them. On one computer there is minicom installed and on another I have compiled and successfully insmoded the below shown module. But when I type on minicom, it doesnt show anything (by the command 'dmesg') on the other computer where my module is loaded!

Kindly help me debug this code.
_______________________________________________________________

Code:

#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <asm/io.h>
#include <linux/fs.h>
#define PORT 0x3F8

irq_handler_t isrSerialPort (int irq, void *dev_id, struct pt_regs *regs)
{
    printk ("\n Thank god \n");
    return (irq_handler_t) IRQ_HANDLED;
}

int init_module ()
{
     request_irq (4, (irq_handler_t) isrSerialPort, SA_SHIRQ, "God", (void *)(isrSerialPort));

   outb (0x80, PORT + 3);
   outb (0x03, PORT + 0);
   outb (0x00, PORT + 1);
   outb (0xC7, PORT + 2);
   outb (0x01, PORT + 1);
}

MODULE_LICENSE ("GPL");

TB0ne · 10-21-2009, 11:09 PM

Quote:

Originally Posted by anishakaul

I got a problem with the following interrupt handler code with respect to serial port 1. I have a cable connecting two serial ports of two computers with linux on them. On one computer there is minicom installed and on another I have compiled and successfully insmoded the below shown module. But when I type on minicom, it doesnt show anything (by the command 'dmesg') on the other computer where my module is loaded !

Kindly help me debug this code !!

Kindly don't post the same question twice, a day apart, because you didn't get an answer in your other thread.

Aquarius_Girl · 10-21-2009, 11:16 PM

I posted the same question here because I thought General forum was wrong place for the question to be! Actually I thought moderator will move this question himself, but he didnt, so I posted it here. And there is no way to delete misplaced questions either.

Aquarius_Girl · 10-27-2009, 01:35 AM

Here by I am presenting the fully functional code for serial port RS232 interrupt handler routine.

Code:

#include <linux/kernel.h>
#include <linux/interrupt.h> 
#include <asm/io.h>

#define PORT 0x3F8

void resetRegisters (unsigned long currentlyUnused);
DECLARE_TASKLET     (rs232Tasklet, resetRegisters, 0);

static int times;

irq_handler_t isrSerialPort (int irq, void *dev_id, struct pt_regs *regs)
{
	times++;
	printk (KERN_ALERT "\nisrSerialPort called %d ", times);

	tasklet_schedule (&rs232Tasklet);
	
	return (irq_handler_t) IRQ_HANDLED;
}

int init_module ()
{
	int result = request_irq (4, (irq_handler_t) isrSerialPort, SA_INTERRUPT, "softbrainISR", NULL);

	outb (0x83, PORT + 3);
	outb (0x01, PORT + 0);
	outb (0x00, PORT + 1);
	outb (0x03, PORT + 3);
	outb (0x01, PORT + 1);
	outb (0x23, PORT + 2);
	outb (0x08, PORT + 4);

	return result;
}

void resetRegisters (unsigned long currentlyUnused)
{
	outb (0x83, PORT + 3);
	outb (0x01, PORT + 0);
	outb (0x00, PORT + 1);
	outb (0x03, PORT + 3);
	outb (0x01, PORT + 1);
	outb (0x23, PORT + 2);
	outb (0x08, PORT + 4);

	printk ("\nU pressed %c ", inb (PORT));
}

void cleanup_module ()
{
	free_irq (4, NULL);
	printk   (KERN_ALERT "\ncleanup_module called\n");
}

MODULE_LICENSE ("GPL");

Anamr · 12-10-2012, 04:19 AM

I tried to compile the following code. And I am encounter some compiling errors(see at the bottom)
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/version.h>
#include <linux/fs.h>
#include <asm/io.h>
#include <asm/signal.h>
#include <linux/irq.h>
#define PORT 0x3F8

void resetRegisters (unsigned long currentlyUnused);
DECLARE_TASKLET (rs232Tasklet, resetRegisters, 0);

static int times;

irq_handler_t isrSerialPort (int irq, void *dev_id, struct pt_regs *regs)
{
times++;
printk (KERN_ALERT "\nisrSerialPort called %d ", times);

tasklet_schedule (&rs232Tasklet);

return (irq_handler_t) IRQ_HANDLED;
}

int __init init_module ()
{
int result = request_irq (4, (irq_handler_t) isrSerialPort, SA_INTERRUPT, "softbrainISR", NULL);

outb (0x83, PORT + 3);
outb (0x01, PORT + 0);
outb (0x00, PORT + 1);
outb (0x03, PORT + 3);
outb (0x01, PORT + 1);
outb (0x23, PORT + 2);
outb (0x08, PORT + 4);

return result;
}

void resetRegisters (unsigned long currentlyUnused)
{
outb (0x83, PORT + 3);
outb (0x01, PORT + 0);
outb (0x00, PORT + 1);
outb (0x03, PORT + 3);
outb (0x01, PORT + 1);
outb (0x23, PORT + 2);
outb (0x08, PORT + 4);

printk ("\nU pressed %c ", inb (PORT));
}

void __exit cleanup_module ()
{
free_irq (4, NULL);
printk (KERN_ALERT "\ncleanup_module called\n");
}

-------------------------------------------------------------------------------------------------------------------

Error- 2
user@-desktop:~/Desktop/an/serialint$ make -C /usr/src/linux-headers-2.6.28-11-generic/ SUBDIRS=${PWD} modules
make: Entering directory `/usr/src/linux-headers-2.6.28-11-generic'
CC [M] /home/user/Desktop/an/serialint/serialint.o
/home/user/Desktop/an/serialint/serialint.c:26: warning: function declaration isn’t a prototype
/home/user/Desktop/an/serialint/serialint.c: In function ‘init_module’:
/home/user/Desktop/an/serialint/serialint.c:27: error: ‘SA_INTERRUPT’ undeclared (first use in this function)
/home/user/Desktop/an/serialint/serialint.c:27: error: (Each undeclared identifier is reported only once
/home/user/Desktop/an/serialint/serialint.c:27: error: for each function it appears in.)
/home/user/Desktop/an/serialint/serialint.c: At top level:
/home/user/Desktop/an/serialint/serialint.c:54: warning: function declaration isn’t a prototype
make[1]: *** [/home/user/Desktop/an/serialint/serialint.o] Error 1
make: *** [_module_/home/user/Desktop/an/serialint] Error 2
make: Leaving directory `/usr/src/linux-headers-2.6.28-11-generic'

Can You help me out to resolve these errors.
The makefile that i used is
--------------------------------------------------------------------------------------
ifneq (${KERNELRELEASE},)
obj-m := serialint.o

else
KERNEL_SOURCE := /usr/src/linux-headers-2.6.28-11-generic/
PWD := $(shell pwd)
default:
${MAKE} -C ${KERNEL_SOURCE} SUBDIRS=${PWD} modules

clean:
${MAKE} -C ${KERNEL_SOURCE} SUBDIRS=${PWD} clean
endif

Aquarius_Girl · 12-10-2012, 04:41 AM

My Makefile is as follows, but AFAIR I had compiled this on openSUSE 10.3 with kernel version 2.6.22. Your kernel version is different.

Code:

obj-m += serialPortISR.o

all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

Quote:

Originally Posted by Anamr

/home/user/Desktop/an/serialint/serialint.c:27: error: ‘SA_INTERRUPT’ undeclared (first use in this function)

I just now downloaded the source of kernel 2.6.22 and looked in its interrupt.h.

Code:

#define SA_INTERRUPT		deprecated_irq_flag(IRQF_DISABLED)
#define SA_SAMPLE_RANDOM	deprecated_irq_flag(IRQF_SAMPLE_RANDOM)
#define SA_SHIRQ		deprecated_irq_flag(IRQF_SHARED)
#define SA_PROBEIRQ		deprecated_irq_flag(IRQF_PROBE_SHARED)
#define SA_PERCPU		deprecated_irq_flag(IRQF_PERCPU)

#define SA_TRIGGER_LOW		deprecated_irq_flag(IRQF_TRIGGER_LOW)
#define SA_TRIGGER_HIGH		deprecated_irq_flag(IRQF_TRIGGER_HIGH)
#define SA_TRIGGER_FALLING	deprecated_irq_flag(IRQF_TRIGGER_FALLING)
#define SA_TRIGGER_RISING	deprecated_irq_flag(IRQF_TRIGGER_RISING)
#define SA_TRIGGER_MASK		deprecated_irq_flag(IRQF_TRIGGER_MASK)

That #define SA_INTERRUPT is there but it is listed as deprecated.

And now I checked the interrupt.h of kernel 3.2.1, this #define is NOT there at all.

Following is the list of different interrupt type flags listed in the interrupt.h of the latest kernel 3.2.1. You can use the one that suits you.

Code:

/*
 * These flags used only by the kernel as part of the
 * irq handling routines.
 *
 * IRQF_DISABLED - keep irqs disabled when calling the action handler.
 *                 DEPRECATED. This flag is a NOOP and scheduled to be removed
 * IRQF_SAMPLE_RANDOM - irq is used to feed the random generator
 * IRQF_SHARED - allow sharing the irq among several devices
 * IRQF_PROBE_SHARED - set by callers when they expect sharing mismatches to occur
 * IRQF_TIMER - Flag to mark this interrupt as timer interrupt
 * IRQF_PERCPU - Interrupt is per cpu
 * IRQF_NOBALANCING - Flag to exclude this interrupt from irq balancing
 * IRQF_IRQPOLL - Interrupt is used for polling (only the interrupt that is
 *                registered first in an shared interrupt is considered for
 *                performance reasons)
 * IRQF_ONESHOT - Interrupt is not reenabled after the hardirq handler finished.
 *                Used by threaded interrupts which need to keep the
 *                irq line disabled until the threaded handler has been run.
 * IRQF_NO_SUSPEND - Do not disable this IRQ during suspend
 * IRQF_FORCE_RESUME - Force enable it on resume even if IRQF_NO_SUSPEND is set
 * IRQF_NO_THREAD - Interrupt cannot be threaded
 * IRQF_EARLY_RESUME - Resume IRQ early during syscore instead of at device
 *                resume time.
 */

Also, for a new question I suggest you to open a new thread to get better attention.

Anamr · 12-11-2012, 01:57 AM

Hi, thanks for the inputs. Yup i referred the latest source code 3.6.9 interrupt.h and used IRQF_IRQPOLL. Also printk ("\nU pressed %c ", inb (PORT)); was not printing any character. I think the baud rate is not correctly configured.

I figured out for 9600 baud (x86 PC16550D), i should set
outb (0x0C, PORT + 0);
outb (0x00, PORT + 1);
and it is working fine.

Aquarius_Girl · 12-11-2012, 02:09 AM

Am glad I could help you.
Thanks for following up.

Anamr · 12-27-2012, 01:31 AM

Hello,

Hi, taking the simple serial driver in irq mode further to writing a simple minicomm like user application.

I wrote a simple minicomm like user application that would transmit and receive characters on a console. Two threads one for receiver that continuously polls (calls the read function) the serial driver and another polls for user data in(use scanf)and writes character by character to serial driver when user enters data.

By above method i have to infinitely poll(call read function of serial driver) to check if serial driver has any data.
This is inefficient way.

So I wanted to know a possible concept in which kernel driver asynchronously sends signal or informs user application about received data availability. It would be great if you could give some pointers on this. or suggest the design for simple [(serial driver in irq mode) to (user application)] , asynchronous communication.

Thank you.

Aquarius_Girl · 12-27-2012, 05:32 AM

Quote:

Originally Posted by Anamr

By above method i have to infinitely poll(call
read function of serial driver) to check if serial driver has any
data.
This is inefficient way.

???

You just have to pass the data from the kernel space to the user
space.
The interrupt handler is already there, which means that when you
press a key on the keyboard the above program will display that
particular key id and you just have to pass that data to the user
space.

Check this out:
http://www.gnugeneration.com/mirrors...api/r4208.html

Also, for new questions start a new thread in a relevant sub forum.

dgashu · 12-31-2012, 11:42 PM

Hi Anisha Kaul,

For debugging purpose just do an loop-back on the cable[by shorting the RX & TX pin] and test
with your application . With this you can figure out if at-least ur code is pumping the data to serial port .....

dgashu · 12-31-2012, 11:44 PM

Sorry Missed the point that it is marked as solved !!!

Aquarius_Girl · 01-01-2013, 12:36 AM

Quote:

Originally Posted by dgashu

Sorry Missed the point that it is marked as solved !!!

Nevermind, it was indeed solved - 3 years back!

Thanks for bothering though.