From mboxrd@z Thu Jan  1 00:00:00 1970
From: Grant Edwards <grant.b.edwards@gmail.com>
Subject: Re: How to disable the transmit FIFO?
Date: Thu, 18 Nov 2010 22:31:55 -0600
Message-ID: <20101119043155.GA17198@grante>
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To: Ted Ts'o <tytso@mit.edu>
Cc: Michael Haardt <michael@moria.de>, linux-serial@vger.kernel.org

On Thu, Nov 18, 2010 at 08:25:23PM -0500, Ted Ts'o wrote:
> On Thu, Nov 18, 2010 at 08:05:56PM +0000, Grant Edwards wrote:
> > On 2010-11-18, Michael Haardt <michael@moria.de> wrote:
> > >> > I miss a way to disable the transmit FIFO.
> > >>
> > >> From userspace or from within a kernel driver?
> > >
> > > From userspace.
> > 
> > $ man setserial
> 
> Specifically, if you use setserial to configure a serial port so that
> its UART is a 16450, it will force the transmit FIFO to be unused.

You can also leave the UART type as 16[56]50 and set the tx fifo
threshold to 1.  That way you're only taking half the hit on interrupt
overhead.

-- 
Grant