linux-kernel - Re: How to handle console devices

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Message-ID: <20090929234733.5b9fbc67@lxorguk.ukuu.org.uk>
Date:	Tue, 29 Sep 2009 23:47:33 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Jason Wessel <jason.wessel@...driver.com>,
	USB list <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: How to handle console devices

> I don't know what the best way is to accomplish this.  Create dummy
> inode and file structs and pass them to the usual tty_open() routine?  
> (But then what about hangup event handling?)  What do you think?

What I long term envisioned was that 

- Every tty (or at least every interesting tty) would have a tty_port
  object for the hardware  [done now for all consoles but vt]
- Every tty port object would have an "output" method
- The tty->termios would move to the tty_port
- The tty receive buffers would move to the tty_port (only needed for a
  console that supports input)

At that point
- The tty lock/refcount isn't needed all the time for the receive data
  paths which speeds it up a fair bit
- A console can be implemented without a tty_struct anywhere in sight
- Flow control and speed setting can be done on hardware generically on
  resume paths

That fixes the lifetime and magic object invention issues that plague the
current console.

I still think that is the right way to fix it.

Alan
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