linux-kernel - Re: Question about TTY_DO_WRITE

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Message-ID: <20081120131726.2636b559@lxorguk.ukuu.org.uk>
Date:	Thu, 20 Nov 2008 13:17:26 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Thomas Pfaff <tpfaff@....com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Question about TTY_DO_WRITE_WAKEUP

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.

Alan
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