linux-kernel - Re: Question about TTY_DO_WRITE

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Date:	Thu, 20 Nov 2008 15:09:43 +0100 (CET)
From:	Thomas Pfaff <tpfaff@....com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	linux-kernel@...r.kernel.org
Subject: Re: Question about TTY_DO_WRITE_WAKEUP


On Thu, 20 Nov 2008, Alan Cox wrote:

> On Thu, 20 Nov 2008 11:06:19 +0100 (CET)
> Thomas Pfaff <tpfaff@....com> wrote:
> 
> > I have written a program that reads and writes data to the serial uart using 
> > async io.
> > Unfortunately it does not work properly because a SIGIO is never gerated when 
> > output becomes possible, the reason is that TTY_DO_WRITE_WAKEUP is not set for 
> > most of the tty drivers. After i set the bit in serial_core.c the program works 
> > as expected.
> > Now i wonder why TTY_DO_WRITE_WAKEUP is almost always disabled ?
> 
> Almost nobody uses SIGIO based I/O, especially on serial so I'm not
> actually suprised by this one. If you've got patches that fix it then
> please send them in.

Is the TTY_DO_WRITE_WAKEUP bit some kind of cruft that can be removed entirely 
or should i generate a patch for serial devices only ?

Removing it seems to be cleaner to me but i am unsure if it will break some 
other stuff.
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