MIME-Version: 1.0
In-Reply-To: <AANLkTi=SkVv4tYUuAr9n03iYFdTJQr7wQnFaodrkHpom@mail.gmail.com>
References: <20100622232108.26752ff8@lxorguk.ukuu.org.uk> <1277462596.2143.101.camel@itpsd6lap>
 <20100625120329.1303aa61@lxorguk.ukuu.org.uk> <1282683470.8020.66.camel@itpsd6lap>
 <20100824211016.GA7176@suse.de> <1282687797.8020.108.camel@itpsd6lap>
 <20100824222035.GA10625@suse.de> <1282690232.8020.116.camel@itpsd6lap>
 <20100824225703.GA5913@suse.de> <20100825002221.68fc09a4@lxorguk.ukuu.org.uk>
 <20100824231241.GA6971@suse.de> <AANLkTi=SkVv4tYUuAr9n03iYFdTJQr7wQnFaodrkHpom@mail.gmail.com>
From: Kay Sievers <kay.sievers@vrfy.org>
Date: Wed, 25 Aug 2010 09:48:23 +0200
Message-ID: <AANLkTimTXKTHqmomfuTQMosPMyhrGLFk7YrEJikpPm6e@mail.gmail.com>
Subject: Re: [PATCH] detour TTY driver - now ttyprintk
To: Greg KH <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, Samo Pogacnik <samo_pogacnik@t-2.net>,
        linux kernel <linux-kernel@vger.kernel.org>,
        linux-embedded <linux-embedded@vger.kernel.org>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1608
Lines: 38

On Wed, Aug 25, 2010 at 09:40, Kay Sievers <kay.sievers@vrfy.org> wrote:
> On Wed, Aug 25, 2010 at 01:12, Greg KH <gregkh@suse.de> wrote:
>> On Wed, Aug 25, 2010 at 12:22:21AM +0100, Alan Cox wrote:
>>> > No, it does cover that.  You should be able to do that with a simple
>>> > console redirection to /dev/kmsg  What happened when you tried to do
>>> > that?
>>>
>>> stty: standard input: Inappropriate ioctl for device
>>
>> Kay, how does systemd handle the kmsg console redirection?
>
> Systemd does not steal the console, this is done by plymouth, in the
> same way blogd can do that. It uses a pty and rewrites the messages.
>
> Systemd does pass syslog to the kernel buffer during early boot. Init
> provides /dev/log. With systemd, the started services usually don't
> get the console connected, but use syslog anyway or the stdout/err
> gets redirected to syslog.
>
> With systemd the console is not too useful because we start everything
> in parallel. If all the services would put out stuff there like sysv
> did, it would look like a real mess.

Or isn't that what you asked for? We just write the stuff that arrives
at syslog to /dev/kmsg to put things in the kernel log buffer.

Also initrds are usually using
  exec < /dev/console > /dev/kmsg 2>&1
to get stuff directly to the kernel buffer.

What does /dev/ttyprintk offer on top of that?

Kay
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/