ioctl fails....

ioctl fails....

[joy]

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     Hi,

I'm trying to do some low level data transmission using the parallel
port .in Debian, it is /dev/par0
my source is attached .perror gives me "invalid argument". if I change
the file being
opened to say, lp0, it gives me "bad file descriptor".
should I use ioperm() even in this case?
and also,is it guaranteed that the parallel port is assigend par0(I have
only one P port)?

Thanx in advance,
Joy.M.Monteiro.




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#include<linux/ppdev.h>
#include<stdlib.h>
#include<unistd.h>
#include<linux/parport.h>
#include<time.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<linux/ioctl.h>

main()
{
	int filedes;
	char data=0xff;
	struct timespec time;
	filedes=open("/dev/par0",O_RDWR);
	if(ioctl(filedes,PPCLAIM)==-1)
		perror("OPEN");
	
	if(ioctl(filedes, PPWDATA, &data)==-1)
		perror("Hi");
	time.tv_sec=1;
	time.tv_nsec=1000;
	nanosleep(&time,NULL);
	close(filedes);
	return;
}
	
	

Re: ioctl fails....

[Jan-Benedict Glaw]

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On Sun, 2004-05-16 10:43:26 +0530, joy <gracecott@sancharnet.in>
wrote in message <40A6F876.50405@sancharnet.in>:
> #include<linux/ppdev.h>
> #include<stdlib.h>
> #include<unistd.h>
> #include<linux/parport.h>

parport.h shouldn't be needed.

> #include<time.h>
> #include<sys/types.h>
> #include<sys/stat.h>
> #include<fcntl.h>
> #include<linux/ioctl.h>

For a small program I wrote, these headers were sufficient:

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <linux/ppdev.h>

Generally, try to keep the number of needed OS dependand headers small.
That keeps you informed about that needs to be ported if you ever need
to go to another OS.

> main()
> {
> 	int filedes;
> 	char data=0xff;
> 	struct timespec time;
> 	filedes=open("/dev/par0",O_RDWR);
> 	if(ioctl(filedes,PPCLAIM)==-1)
> 		perror("OPEN");
> 	
> 	if(ioctl(filedes, PPWDATA, &data)==-1)
> 		perror("Hi");
> 	time.tv_sec=1;
> 	time.tv_nsec=1000;
> 	nanosleep(&time,NULL);
> 	close(filedes);
> 	return;
> }

The code itself looks okay technically (well, early exit on failure
would be nice:), but I suspect that you're using a wrong device. Is your
device /dev/par0 a char-dev with major=99 and minor=0? Is the ppdev
driver loaded?

MfG, JBG

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