[Linux-parport] Trouble setting up an EPP connection

[ofir]

Hi all,

I write an application (in user space) that sends and receive data using
the parport driver. I want to use the EPP protocol.
I'm having trouble setting up the connection.

I basically use

  mode = IEEE1284_MODE_EPP;

and then either:

  ioctl( fd, PPSETMODE, &mode)

In which case "nothing happens" a read blocks, and a send operation
generates no response on the other side.

or:

  ioctl( fd, PPNEGOT, &mode)

which fails with "Input/output error" from perror

Here are the details:

[PC A]
OS: Fedora core2 (kernel 2.6.5-1.358)
Port Type: Parallel Port ECP/EPP

Output of dmesg | grep parport :
parport0: PC-style at 0x378 [PCSPP,TRISTATE,EPP]
parport0: PC-style at 0x378 [PCSPP,TRISTATE,EPP]
lp0: using parport0 (polling).
parport0: PC-style at 0x378 [PCSPP,TRISTATE,EPP]
parport_negotiate returned: 1

[PC B]
OS: Debian (kernel 2.6.7-1-386)
Port Type: Parallel Port ECP/EPP

Output of dmesg | grep parport :
parport: PnPBIOS parport detected.
parport0: PC-style at 0x378, irq 7 [PCSPP,TRISTATE,EPP]
parport: PnPBIOS parport detected.
parport0: PC-style at 0x378, irq 7 [PCSPP,TRISTATE,EPP]
lp0: using parport0 (interrupt-driven).

The problem is that I can't set the negotiation mode for the communication.
1) Do I need to configure Linux in some way to enable the EPP capabilities on
    the system?
2) Is there some thing I'm not doing right (program-wise)?
    I included my source please take a look.

(The application serves as both the receiving and sending app.
 Each instance of the app is set as receiver or sender depending on the
 parameter it is run with.)
example:
   (Setting a sending instance on parport1)
   app -p /dev/parport1 -s

  (Setting a receiving instance on parport0 [default])
   app

The source code for the application:

#include <linux/parport.h>
#include <linux/ppdev.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <stdio.h>

#define FALSE	0
#define TRUE	1

int open_parport(char* device_name, int flags,int mode)
{
	int fd = -1;

	/* Open the device for IO */
	if((fd = open(device_name,flags)) == -1)
	{
		perror(device_name);
		return -1;
	}

	/* Claim device */
	if ( ioctl (fd, PPCLAIM) )
	{
		perror ("PPCLAIM");
		close (fd);
		return -1;
	}

	/* Set the communication mode (protocol) for the device */
	if ( ioctl(fd, PPSETMODE, &mode) )
	{
		perror ("PPSETMODE");
		close (fd);
		return -1;
	}

	/* 	I used PPNEGOT instead of PPSETMODE and got
		"Input/output error" from perror
		When I started using PPSETMODE the error
		was gone but nothing was happening

	if ( ioctl (fd, PPNEGOT, &mode))
or:	{
		perror("error: device not IEEE 1284 compliant");
		close (fd);
		return -1;
	}
*/
	return fd;
}

int main(int argc, char** argv)
{
	int fd = 0;
	int sending = FALSE;		/* TRUE=send FALSE=receive */
	int mode = IEEE1284_MODE_EPP;
	int res_size = 0;
	size_t i = 0;
	size_t data_len = 30;
	char device_name[1024] = {"/dev/parport0"};
	unsigned char buffer[36];

	if(argc > 1)
	{
		for(i = 1; i < argc ; i++)
		{
			switch(argv[i][1])
			{
			case 'p':
				strcpy(device_name,argv[++i]);
				break;
			case 's':
				sending = TRUE;
				break;
			}
		}
	}

	if(sending)	/* Sender */
	{
		/*Fill buffer with 'X' and 'O' for testing */
		for(i = 0; i < data_len ; i++)	
			buffer[i] = (i%2) ? 'X' : 'O';       

		if((fd = open_parport(device_name, O_RDWR, mode)) == -1)
			return -1;

		if((res_size = write(fd,buffer,data_len)) == -1)
		{
			perror("Failed to write device");
			exit(-1);
		}
	}
	else		/* Receiver */
	{
		if((fd = open_parport(device_name, O_RDONLY, mode)) == -1)
			return -1;

		if( (res_size = read(fd,buffer,data_len)) == -1)
		{
			perror("Failed to read device");
			exit(-1);
		}
		buffer[res_size] = '\0';
		printf("Buffer received: %s\n", buffer);
	}

	ioctl(fd, PPRELEASE);
	close(fd);

	return 0;
}