Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751903AbaBEOTL (ORCPT ); Wed, 5 Feb 2014 09:19:11 -0500 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:53692 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750971AbaBEOTJ (ORCPT ); Wed, 5 Feb 2014 09:19:09 -0500 Message-ID: <52F24858.4020208@hurleysoftware.com> Date: Wed, 05 Feb 2014 09:19:04 -0500 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: David Herrmann CC: Hannes Reinecke , systemd Mailing List , Kay Sievers , linux-kernel , Greg Kroah-Hartman , Jiri Slaby Subject: Re: [systemd-devel] [PATCH] tty: Set correct tty name in 'active' sysfs attribute References: <1391595106-86957-1-git-send-email-hare@suse.de> <52F2424A.609@hurleysoftware.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch won't get very far if not addressed to the actual maintainers [ +cc Greg Kroah-Hartman, Jiri Slaby] On 02/05/2014 09:05 AM, David Herrmann wrote: > Hi > > On Wed, Feb 5, 2014 at 2:53 PM, Peter Hurley wrote: >> On 02/05/2014 07:53 AM, David Herrmann wrote: >>> >>> Hi >>> >>> On Wed, Feb 5, 2014 at 11:11 AM, Hannes Reinecke wrote: >>>> >>>> The 'active' sysfs attribute should refer to the currently >>>> active tty devices the console is running on, not the currently >>>> active console. >>>> The console structure doesn't refer to any device in sysfs, >>>> only the tty the console is running on has. >>>> So we need to print out the tty names in 'active', not >>>> the console names. >>>> >>>> Cc: Lennart Poettering >>>> Cc: Kay Sievers >>>> Signed-off-by: Werner Fink >>>> Signed-off-by: Hannes Reinecke >>>> --- >>>> drivers/tty/tty_io.c | 14 ++++++++++++-- >>>> 1 file changed, 12 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c >>>> index c74a00a..17db8ca 100644 >>>> --- a/drivers/tty/tty_io.c >>>> +++ b/drivers/tty/tty_io.c >>>> @@ -3545,9 +3545,19 @@ static ssize_t show_cons_active(struct device >>>> *dev, >>>> if (i >= ARRAY_SIZE(cs)) >>>> break; >>>> } >>>> - while (i--) >>>> + while (i--) { >>>> + const struct tty_driver *driver; >>>> + const char *name = cs[i]->name; >>>> + int index = cs[i]->index; >>>> + >>>> + driver = cs[i]->device(cs[i], &index); >>>> + if (driver) { >>>> + index += driver->name_base; >>>> + name = driver->name; >>>> + } >>>> count += sprintf(buf + count, "%s%d%c", >>>> - cs[i]->name, cs[i]->index, i ? ' >>>> ':'\n'); >>>> + name, index, i ? ' ':'\n'); >>>> + } >>> >>> >>> Nice catch and indeed, systemd already relies on these names to be >>> identical to their char-dev name. Fortunately, VTs and most serial >>> devices register the console with the same name as the TTY, so we're >>> fine. >> >> >> What device did this trip over? > > I haven't seen one so far, but to me it's a coincident, not something > we should rely on. > >> Also, this file is not private to systemd. Maybe these changes should >> be forked into a different sysfs attribute, "active_devices"? > > What's the use-case to return the name of the console-driver? There is > no way for user-space to read active console-drivers anywhere so I > think returning the TTY makes more sense. We already have working > user-space that can spawn gettys on active consoles via this file. I > am open to change this to "active_devices" as the existing interface > was clearly not designed to return the device-names. > > However, given the fact that both matched so far, I think changing the > existing interface to the only user I am aware of is better than > adding a new interface just to keep this unused attribute. But > obviously it's the maintainer's/your decision and you might know > user-space which requires the console-names instead of the tty-names. > So please let us know which way to go as we would like to see a > reliable way to match active consoles to TTY devices for automated > getty-startup. Sure, I get it. Just wanted to point out the obvious right up front so that if it turns out there is another userspace dependency and this gets rewound, possibly across future -stable kernels, the fallout could get ugly. Regards, Peter Hurley PS - The "active" attribute won't be unused; old systemd's will still depend on it, yes? -- 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/