tty line discipline

[Rabih ElMasri]

hi,

I am trying to assign a new line discipline to ttyS0 from within the
kernel-space. During the initialization of my module I do the
following:

fp=filp_open(dev,O_RDWR | O_NOCTTY,0);
tty=fp->private_data; //the tty_struct

then I initialize the fields of the new line discipline (ldisc). and
assign it to the tty_struct:

tty->ldisc=ldisc;

It works fine the first time I insert the module, but gets problems
with tty->count if I insert it again.

I tried to call the tty_ioctl function of tty_io.c (with flag
TIOCSETD) using the corresponding field in the file structure
(fp->f_op->ioctl(..)), but it seems to expect a call from user-space,
and returns -EFAULT due to the get_user macro.

I would really appreciate it if someone can tell me how to deal with
this problem.

Regards,
Rabih
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[Arjan van de Ven]

On Wed, 2005-10-19 at 13:55 +0200, Rabih ElMasri wrote:
> hi,
>
> I am trying to assign a new line discipline to ttyS0 from within the
> kernel-space.

why? You don't describe what you want to solve, only how you want to do
it... it might be entirely the wrong solution for a simple problem..

> During the initialization of my module I do the
> following:

you forgot to attach the full source of your module or point to URL with
that. That is basically rule nr 1 when posting about problems with
out-of-kernel modules; how else are people supposed to help you?

[Rabih ElMasri]

Thank you Arjan for the remarks. I want to establish communication
between a host and a controller. The controller is connected to the
serial port ttyS0. I want to be able to specify how the driver
receives and sends the data. I thought this would require a line
discipline because a driver for ttyS0 already exists. Please correct
me if I was wrong.

Previously, I used to initialize the module and register the line
discipline to N_MOUSE. Then I would run a C-file from user space with
the code:

i=N_MOUSE;
ioctl(fd,TIOCSETD,&i);

This would assign the line discipline to ttyS0 successfully. Now, I
want to establish communication directly from kernel space.

As can be seen from the attached source file, the only fields from the
tty_ldisc structure that I'm using are receive_buf (tl_tty_receive)
and write_wakeup(tl_tty_wakeup).

If the problem is still unclear please tell me.