linux-kernel - Re: serial device and fsync

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Message-ID: <20090525143603.3a741658@lxorguk.ukuu.org.uk>
Date:	Mon, 25 May 2009 14:36:03 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Ramagudi Naziir <naziirr@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: serial device and fsync

On Mon, 25 May 2009 12:50:22 +0300
Ramagudi Naziir <naziirr@...il.com> wrote:

> Hi all,
> 
> I need to write(2) a certain character to a serial device (using the
> standard /dev/ttySx), and make sure it was transferred to the device
> before I continue. I tried fsync(2), but that failed (does fsync even
> apply to character devices or only block devices ?).

Block devices
> 
> Any idea ?

Most hardware UARTs actually can't do this but the kernel will do its
best. The POSIX interface you want is tcdrain(fd). Quite why POSIX didn't
use fsync is a very good question.
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