From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <ian.campbell@citrix.com>
Subject: Re: [PATCH] xenconsole: Allow non-interactive use
Date: Thu, 23 Jul 2015 09:48:50 +0100
Message-ID: <1437641330.19412.37.camel@citrix.com>
References: <1437584888-9074-1-git-send-email-martin@lucina.net>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta3.messagelabs.com ([195.245.230.39])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <prvs=639e45c83=Ian.Campbell@citrix.com>)
	id 1ZICBS-0002rn-V2
	for xen-devel@lists.xenproject.org; Thu, 23 Jul 2015 08:48:55 +0000
In-Reply-To: <1437584888-9074-1-git-send-email-martin@lucina.net>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Martin Lucina <martin@lucina.net>, xen-devel@lists.xenproject.org
Cc: Ian Jackson <ian.jackson@eu.citrix.com>, Wei Liu <wei.liu2@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>
List-Id: xen-devel@lists.xenproject.org

On Wed, 2015-07-22 at 19:08 +0200, Martin Lucina wrote:
> If xenconsole is run with stdin closed or redirected to /dev/null,
> console_loop() will return immediately due to failure to read from
> STDIN_FILENO. This patch tests if stdin and stdout are both connected 
> to
> a TTY and, if not, xenconsole will not attempt to read from stdin or
> modify stdout terminal attributes.
> 
> Existing behaviour when xenconsole is run from a terminal does not
> change.
> 
> This allows for non-interactive use, eg. running "xl create -c" under
> systemd or piping the output of "xl console" to another command.
> 
> Signed-off-by: Martin Lucina <martin@lucina.net>
> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Cc: Ian Campbell <ian.campbell@citrix.com>
> Cc: Wei Liu <wei.liu2@citrix.com>

Acked-by: Ian Campbell <ian.campbell@citrix.com>

WRT the 4.6 freeze I'm torn between calling this a feature or a bugfix.

A pair of nits, which probably aren't worth acting on:

> @@ -176,8 +177,13 @@ static int console_loop(int fd, struct xs_handle
> *xs, char *pty_path)
>  		fd_set fds;
>  
>  		FD_ZERO(&fds);
> -		FD_SET(STDIN_FILENO, &fds);
> -		max_fd = STDIN_FILENO;
> +		if (interactive) {
> +			FD_SET(STDIN_FILENO, &fds);
> +			max_fd = STDIN_FILENO;
> +		}
> +		else {
> +			max_fd = -1;
> +		}

Looking at the rest of the file and tools/console subtree it seems the
prevailing coding style is:

		} else
                	                max_fd = -1;

(i.e. } brace on the same line as the else and no {} for single
statements after an else).

But maybe it would be better to set max_fd = -1 on declaration and do
the max dance here as with the following cases?

Ian.