Re: Change number of tty devices

From: Jason Cox
Date: Wed Apr 21 2004 - 21:25:04 EST

On Wed, 21 Apr 2004 21:14:38 +0100 (BST)
James Simmons <jsimmons@xxxxxxxxxxxxx> wrote:

> > Often, I have wondered what the need for 64 tty devices in /dev is.
> > I began tinkering with the code and am wondering why it's not user
> > configurable. I came up with a quick patch to add it as an option
> > under drivers/char/Kconfig. I also made a lower bound of 12. If this
> > is an idea worth pursuing, please let me know. If this idea has been
> > rejected before, I apologize. What do you think of this idea?
> The reason for 64 is that the major number is shared between the
> serial tty and VT tty drivers. The first 64 to Vts and the rest to
> serial devices.

First off, thanks for the reply. Does lowering the number of tty devices
interfer with the creation of serial consoles? Can't they start at the
same major number without an issue?

> What is even more is that there exist ioctls that return shorts
> which means only 16 VCs can be accounted for on a VT.

So is my limit wrong? Should I up the lower limit to 16 to account for

> When the kernel supports multi-desktop systems we will have to deal
> with the serial and VT issue. Most likely the serial tty drivers will
> be given a different major number.

Why isn't this done now?

> I personally believe that because
> of the 16 bit limit that there should be 16 VCs per VT terminal.

That does make sense.

Just a side note: I have been running with 12 (0 - 11) tty devices
without issue. I haven't tried a serial console, but will shortly, just
to see if it interferes with serial console creation.

Jason Cox

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