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Date: 20 May 2001 11:53:00 +0200
From: kaih@khms.westfalen.de (Kai Henningsen)
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Subject: Re: no ioctls for serial ports? [was Re: LANANA: To Pending Device Num
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pavel@suse.cz (Pavel Machek)  wrote on 19.05.01 in <20010519214321.A9550@atrey.karlin.mff.cuni.cz>:

> 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