On Sat, Jan 11, 2020 at 3:21 AM Josh Triplett <josh@xxxxxxxxxxxxxxxx> wrote:
>
> Virtual machines and containers often use an ACPI power button event to
> tell the machine to shut down gracefully.
>
> Provide an optional, extremely lightweight way to handle this event by
> signaling init directly, rather than running a separate daemon (such as
> acpid or systemd-logind) that adds to startup time and VM image
> complexity.
Well, I'm not convinced.
Even though the patch looks straightforward, the approach really is
quite not so conceptually and honestly it looks like a band-aid.
Also I'm not quite sure why the ACPI button driver is the target of
this and not the input layer, for instance.
> By default, the power button will continue to notify userspace through
> the input layer. With the button.power_signal parameter set, the
> power button will instead send the configured signal to init. (For
> instance, sending SIGINT will make the power button simulate
> ctrl-alt-del.)
>
> Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
> drivers/acpi/button.c | 11 +++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index ade4e6ec23e0..bbb598e148f4 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -450,6 +450,12 @@
> firmware feature for flushing multiple hpte entries
> at a time.
>
> + button.power_signal=
> + [ACPI] When the power button is pressed, send this
> + signal number to the init process. If set to 0
> + (default), do not send a signal.
> + Format: integer
> +
> c101= [NET] Moxa C101 synchronous serial card
>
> cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
> diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
> index b758b45737f5..923259f132d6 100644
> --- a/drivers/acpi/button.c
> +++ b/drivers/acpi/button.c
> @@ -14,6 +14,7 @@
> #include <linux/init.h>
> #include <linux/types.h>
> #include <linux/proc_fs.h>
> +#include <linux/sched/signal.h>
> #include <linux/seq_file.h>
> #include <linux/input.h>
> #include <linux/slab.h>
> @@ -167,6 +168,10 @@ static unsigned long lid_report_interval __read_mostly = 500;
> module_param(lid_report_interval, ulong, 0644);
> MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
>
> +static int power_signal __read_mostly = 0;
> +module_param(power_signal, int, 0644);
> +MODULE_PARM_DESC(power_signal, "Power button sends this signal to init");
> +
> /* --------------------------------------------------------------------------
> FS Interface (/proc)
> -------------------------------------------------------------------------- */
> @@ -426,6 +431,12 @@ static void acpi_button_notify(struct acpi_device *device, u32 event)
> if (button->suspended)
> break;
>
> + if (power_signal
> + && button->type == ACPI_BUTTON_TYPE_POWER) {
> + kill_cad_pid(power_signal, 1);
> + break;
> + }
> +
> keycode = test_bit(KEY_SLEEP, input->keybit) ?
> KEY_SLEEP : KEY_POWER;
> input_report_key(input, keycode, 1);
> --
> 2.25.0.rc2
>
