How to use serial ports from a kernel module.

How to use serial ports from a kernel module.

[ian]

Hi guys,

I'd like to use one of the serial ports on my embedded device from a
module (so I can write an input driver for the buttonpad on my PDA).

I need to be able to set the data type to 8O1 and set the port speed,
and send and receive data.

Whats the proper way to do this? Ideally I'd want to prevent userspace
being able to use the port which has the keypad connected, but not touch
the other two ports.

Thanks,

-Ian

Re: How to use serial ports from a kernel module.

[Guennadi Liakhovetski]

On Sat, 26 Jan 2008, ian wrote:

> I'd like to use one of the serial ports on my embedded device from a
> module (so I can write an input driver for the buttonpad on my PDA).
> 
> I need to be able to set the data type to 8O1 and set the port speed,
> and send and receive data.
> 
> Whats the proper way to do this? Ideally I'd want to prevent userspace
> being able to use the port which has the keypad connected, but not touch
> the other two ports.

You need to write a line discipline... have a look here: 
http://www.linux.it/~rubini/docs/serial/serial.html

Thanks
Guennadi
---
Guennadi Liakhovetski

Re: How to use serial ports from a kernel module.

[ian]

On Sat, 2008-01-26 at 21:41 +0100, Guennadi Liakhovetski wrote:

> You need to write a line discipline... have a look here: 
> http://www.linux.it/~rubini/docs/serial/serial.html

Hi,

Thanks for the reply!

What I cant see from that is how one can avoid touching userspace at all
- as far as I can see, only userspace can actually attach a line
discipline to a serial port. I'd like to have this happen in the kernel
so that I dont need some program sitting idly opening the serial device
the whole time.

Thanks,

-Ian!

Re: How to use serial ports from a kernel module.

[Guennadi Liakhovetski]

On Sat, 26 Jan 2008, ian wrote:

> 
> On Sat, 2008-01-26 at 21:41 +0100, Guennadi Liakhovetski wrote:
> 
> > You need to write a line discipline... have a look here: 
> > http://www.linux.it/~rubini/docs/serial/serial.html
> 
> Hi,
> 
> Thanks for the reply!
> 
> What I cant see from that is how one can avoid touching userspace at all
> - as far as I can see, only userspace can actually attach a line
> discipline to a serial port. I'd like to have this happen in the kernel
> so that I dont need some program sitting idly opening the serial device
> the whole time.

Right, you need a user-space daemon for that. In your original post you 
only said

> > Ideally I'd want to prevent userspace being able to use the port which 
> > has the keypad connected, but not touch the other two ports.

which I understood as "I want to lock this port, and leave the rest 
untouched" and not as "avoid touching userspace at all". I don't think 
you can do it without a user-space programme.

Thanks
Guennadi
---
Guennadi Liakhovetski