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([2a01:e0a:c:37e0:8998:e0cf:68cc:1b62]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4804d8a5b67sm275961735e9.10.2026.01.26.02.48.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 Jan 2026 02:48:51 -0800 (PST) Message-ID: <45526d98-57b6-456e-babc-61b7331318c0@redhat.com> Date: Mon, 26 Jan 2026 11:48:50 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] vt: Add enable module parameter To: Greg Kroah-Hartman Cc: Jiri Slaby , Nicolas Pitre , Calixte Pernot , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org References: <20260126092234.713465-1-jfalempe@redhat.com> <2026012613-cotton-jellied-b67a@gregkh> <48be84fb-bee4-4a22-bde4-0d0c78282f80@redhat.com> <2026012648-vantage-mummified-2a43@gregkh> Content-Language: en-US, fr From: Jocelyn Falempe In-Reply-To: <2026012648-vantage-mummified-2a43@gregkh> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 26/01/2026 11:20, Greg Kroah-Hartman wrote: > On Mon, Jan 26, 2026 at 10:43:35AM +0100, Jocelyn Falempe wrote: >> On 26/01/2026 10:33, Greg Kroah-Hartman wrote: >>> On Mon, Jan 26, 2026 at 10:21:50AM +0100, Jocelyn Falempe wrote: >>>> This allows to build the kernel with CONFIG_VT enabled, and choose >>>> on the kernel command line to enable it or not. >>> >>> This says what is happening, but not why? >>> >>>> Add vt.enable=1 to force enable, or vt.enable=0 to force disable. >>> >>> Why are we using a 1990's technology for a new feature? What is this >>> going to allow to have happen? Who needs/wants this? Who will use it? >>> For what? >> >> The goal is to ease the transition to disable CONFIG_VT. >> >> So if this is merged, you can boot without VT on any Linux distribution, >> without rebuilding the kernel. > > But that's a distro-specific thing, the distro should be enabling or > disabling the option as it needs, it should not be a user-configurable > boot-time selection option as userspace depends entirely on this either > being there or not. Why would you have a kernel with both options but > userspace without that? Actually the userspace side works with or without VT, at least with Fedora, I've my Gnome session in both cases. > >> This option will also allow a distribution to disable VT by default, but >> users that really wants this can enable it on the kernel command line, >> without rebuilding the kernel. > > Why would a user want that? If a user really wants it enabled, why > would userspace even still work and why would they want to not rebuild > the kernel? Rebuilding kernel is not user-friendly, changing a kernel cmdline parameter is much easier. > >> It will also avoid hacky solution in userspace like this: >> https://overhead.neocities.org/blog/systemd-logind-seat/#very-hacky-solutions > > Surely that can't be the only way, why can't userspace just handle this > "properly" if it wants to? There is no way for userspace to disable the tty that are running in the kernel. It can at best ignore them, but for me it's not a proper solution. > >>>> Signed-off-by: Jocelyn Falempe >>>> --- >>>> drivers/tty/Kconfig | 13 +++++++++++++ >>>> drivers/tty/vt/vt.c | 5 +++++ >>>> 2 files changed, 18 insertions(+) >>>> >>>> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig >>>> index 149f3d53b7608..2b94c2710687a 100644 >>>> --- a/drivers/tty/Kconfig >>>> +++ b/drivers/tty/Kconfig >>>> @@ -41,6 +41,19 @@ config VT >>>> If unsure, say Y, or else you won't be able to do much with your new >>>> shiny Linux system :-) >>>> +config VT_ENABLE >>>> + depends on VT >>>> + default y >>>> + bool "enable VT terminal" if EXPERT >>> >>> So no one will ever really use this config option? >>> >>> And you are doing 2 things in this patch, not just one, unlike what the >>> changelog said :( >> >> I can split that in two if you prefer. > > I'm objecting to the patch doing something other than what the changelog > describes, which as you know is not a good thing. > ok, I can fix that in a v2. >> Adding a module parameter, and adding a Kconfig option, to choose the >> default for this module parameter. > > I really don't like adding new module parameters that we are going to > have to now support for forever. Why not just rely on the config option > being there or not as-is? That's why we allowed it to be turned off at > all, because userspace was going to be moved to not need it anymore. > Why would we want to support "both" at the same time in the kernel? > This parameter is there to ease the transition to VT-less system. So by maintaining this few lines of code, it will be possible to deprecate the whole VT in the future. If a module parameter is not a good solution, I'm open to any solution that can disable vt from the kernel command line (userspace init runs to late to disable vt). > thanks, > > greg k-h >