Re: no ioctls for serial ports? [was Re: LANANA: To Pending Device Num

[Kai Henningsen]

[e-mail] (Pavel Machek)  wrote on 19.05.01 in <[e-mail]>:

> I think that plan9 uses something different -- they have ttyS0 and
> ttyS0ctl. This would leave us with problem "how do I get handle to
> ttyS0ctl when I only have handle to ttyS0"?

I've seen this question several times in this thread. I haven't seen the  
obvious answer, though.

Have a new system call:

ctlfd = open_device_control_fd(fd);

If fd is something that doesn't have a control interface (say, it already  
is a control filehandle), this returns an appropriate error code.

This has another benefit, in that you can get control descriptors for  
stuff that doesn't currently have a filename (but does have ioctls), such  
as network sockets.

MfG Kai