Re: [PATCH v2 07/11] input: macsmc-hid: New driver to handle the Apple Mac SMC buttons/lid

Janne Grunau
2025-09-25T21:49:43Z

On Wed, Aug 27, 2025 at 09:22:41PM +1000, James Calligeros wrote:
> From: Hector Martin <marcan@marcan.st>
>
> This driver implements power button and lid switch support for Apple Mac
> devices using SMC controllers driven by the macsmc driver.
>
> In addition to basic input support, this also responds to the final
> shutdown warning (when the power button is held down long enough) by
> doing an emergency kernel poweroff. This allows the NVMe controller to
> be cleanly shut down, which prevents data loss for in-cache data.
>
> Signed-off-by: Hector Martin <marcan@marcan.st>
> Co-developed-by: Sven Peter <sven@kernel.org>
> Signed-off-by: Sven Peter <sven@kernel.org>
> Signed-off-by: James Calligeros <jcalligeros99@gmail.com>
> ---
> MAINTAINERS | 1 +
> drivers/input/misc/Kconfig | 11 ++
> drivers/input/misc/Makefile | 1 +
> drivers/input/misc/macsmc-hid.c | 209 +++++++++++++++++++++++++

I would rename this driver to macsmc-input. I would expect hid driver to
live in drivers/hid/ and use HID report descriptors

> 4 files changed, 222 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2eb23522654dd050262eb06e077587030cc335aa..b3b5220fcd0d4bbef67613c8ee9afa880c0aa45d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2412,6 +2412,7 @@ F: drivers/hwmon/macsmc_hwmon.c
> F: drivers/pmdomain/apple/
> F: drivers/i2c/busses/i2c-pasemi-core.c
> F: drivers/i2c/busses/i2c-pasemi-platform.c
> +F: drivers/input/misc/macsmc-hid.c
> F: drivers/input/touchscreen/apple_z2.c
> F: drivers/iommu/apple-dart.c
> F: drivers/iommu/io-pgtable-dart.c
> diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
> index 0fb21c99a5e3d1230d7f40f99e0c2d360bbe80e8..a430c50e7f63f245bba56bd526026ec7901cf821 100644
> --- a/drivers/input/misc/Kconfig
> +++ b/drivers/input/misc/Kconfig
> @@ -961,4 +961,15 @@ config INPUT_STPMIC1_ONKEY
> To compile this driver as a module, choose M here: the
> module will be called stpmic1_onkey.
>
> +config INPUT_MACSMC_HID
> + tristate "Apple Mac SMC lid/buttons"
> + depends on MFD_MACSMC
> + help
> + Say Y here if you want to use the input events delivered via the
> + SMC controller on Apple Mac machines using the macsmc driver.
> + This includes lid open/close and the power button.
> +
> + To compile this driver as a module, choose M here: the
> + module will be called macsmc-hid.
> +
> endif
> diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
> index d468c8140b93da5bb537e8a3baea2b90e7bb4229..95b8ebbb9ebbe6f3afc9db724d2ebeba1d75d1a6 100644
> --- a/drivers/input/misc/Makefile
> +++ b/drivers/input/misc/Makefile
> @@ -51,6 +51,7 @@ obj-$(CONFIG_INPUT_IQS7222) += iqs7222.o
> obj-$(CONFIG_INPUT_KEYSPAN_REMOTE) += keyspan_remote.o
> obj-$(CONFIG_INPUT_KXTJ9) += kxtj9.o
> obj-$(CONFIG_INPUT_M68K_BEEP) += m68kspkr.o
> +obj-$(CONFIG_INPUT_MACSMC_HID) += macsmc-hid.o
> obj-$(CONFIG_INPUT_MAX77650_ONKEY) += max77650-onkey.o
> obj-$(CONFIG_INPUT_MAX77693_HAPTIC) += max77693-haptic.o
> obj-$(CONFIG_INPUT_MAX8925_ONKEY) += max8925_onkey.o
> diff --git a/drivers/input/misc/macsmc-hid.c b/drivers/input/misc/macsmc-hid.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..c7cd56e5c17f08936cc623f7d3690f27e05012a5
> --- /dev/null
> +++ b/drivers/input/misc/macsmc-hid.c
> @@ -0,0 +1,209 @@
> +// SPDX-License-Identifier: GPL-2.0-only OR MIT
> +/*
> + * Apple SMC input event driver
> + * Copyright The Asahi Linux Contributors
> + *
> + * This driver exposes HID events from the SMC as an input device.
> + * This includes the lid open/close and power button notifications.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/input.h>
> +#include <linux/mfd/core.h>
> +#include <linux/mfd/macsmc.h>
> +#include <linux/module.h>
> +#include <linux/reboot.h>
> +
> +/**
> + * struct macsmc_hid
> + * @dev: Underlying struct device for the HID sub-device
> + * @smc: Pointer to apple_smc struct of the mfd parent
> + * @input: Allocated input_dev; devres managed
> + * @nb: Notifier block used for incoming events from SMC (e.g. button pressed down)
> + * @wakeup_mode: Set to true when system is suspended and power button events should wake it
> + */
> +struct macsmc_hid {
> + struct device *dev;
> + struct apple_smc *smc;
> + struct input_dev *input;
> + struct notifier_block nb;
> + bool wakeup_mode;
> +};
> +
> +#define SMC_EV_BTN 0x7201
> +#define SMC_EV_LID 0x7203
> +
> +#define BTN_POWER 0x01 /* power button on e.g. Mac Mini chasis pressed */
> +#define BTN_TOUCHID 0x06 /* combined TouchID / power button on MacBooks pressed */
> +#define BTN_POWER_HELD_SHORT 0xfe /* power button briefly held down */
> +#define BTN_POWER_HELD_LONG 0x00 /* power button held down; sent just before forced poweroff */
> +
> +static void macsmc_hid_event_button(struct macsmc_hid *smchid, unsigned long event)
> +{
> + u8 button = (event >> 8) & 0xff;
> + u8 state = !!(event & 0xff);
> +
> + switch (button) {
> + case BTN_POWER:
> + case BTN_TOUCHID:
> + if (smchid->wakeup_mode) {
> + if (state)
> + pm_wakeup_hard_event(smchid->dev);
> + } else {
> + input_report_key(smchid->input, KEY_POWER, state);
> + input_sync(smchid->input);
> + }
> + break;
> + case BTN_POWER_HELD_SHORT: /* power button held down; ignore */
> + break;
> + case BTN_POWER_HELD_LONG:
> + /*
> + * If we get here the power button has been held down for a while and
> + * we have about 4 seconds before forced power-off is triggered by SMC.
> + * Try to do an emergency shutdown to make sure the NVMe cache is
> + * flushed. macOS actually does this by panicing (!)...
> + */
> + if (state) {
> + dev_crit(smchid->dev, "Triggering forced shutdown!\n");
> + if (kernel_can_power_off())
> + kernel_power_off();
> + else /* Missing macsmc-reboot driver? */
> + kernel_restart("SMC power button triggered restart");
> + }
> + break;
> + default:
> + dev_warn(smchid->dev, "Unknown SMC button event: %04lx\n", event & 0xffff);
> + }
> +}
> +
> +static void macsmc_hid_event_lid(struct macsmc_hid *smchid, unsigned long event)
> +{
> + u8 lid_state = !!((event >> 8) & 0xff);
> +
> + if (smchid->wakeup_mode && !lid_state)
> + pm_wakeup_hard_event(smchid->dev);
> +
> + input_report_switch(smchid->input, SW_LID, lid_state);
> + input_sync(smchid->input);
> +}
> +
> +static int macsmc_hid_event(struct notifier_block *nb, unsigned long event, void *data)
> +{
> + struct macsmc_hid *smchid = container_of(nb, struct macsmc_hid, nb);
> + u16 type = event >> 16;
> +
> + switch (type) {
> + case SMC_EV_BTN:
> + macsmc_hid_event_button(smchid, event);
> + return NOTIFY_OK;
> + case SMC_EV_LID:
> + macsmc_hid_event_lid(smchid, event);
> + return NOTIFY_OK;
> + default:
> + /* SMC event meant for another driver */
> + return NOTIFY_DONE;
> + }
> +}
> +
> +static int macsmc_hid_probe(struct platform_device *pdev)
> +{
> + struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
> + struct macsmc_hid *smchid;
> + bool have_lid, have_power;
> + int ret;
> +
> + /* Bail early if this SMC neither supports power button nor lid events */
> + have_lid = apple_smc_key_exists(smc, SMC_KEY(MSLD));
> + have_power = apple_smc_key_exists(smc, SMC_KEY(bHLD));
> + if (!have_lid && !have_power)
> + return -ENODEV;
> +
> + smchid = devm_kzalloc(&pdev->dev, sizeof(*smchid), GFP_KERNEL);
> + if (!smchid)
> + return -ENOMEM;
> +
> + smchid->dev = &pdev->dev;
> + smchid->smc = smc;
> + platform_set_drvdata(pdev, smchid);
> +
> + smchid->input = devm_input_allocate_device(&pdev->dev);
> + if (!smchid->input)
> + return -ENOMEM;
> +
> + smchid->input->phys = "macsmc-hid (0)";
> + smchid->input->name = "Apple SMC power/lid events";
> +
> + if (have_lid)
> + input_set_capability(smchid->input, EV_SW, SW_LID);
> + if (have_power)
> + input_set_capability(smchid->input, EV_KEY, KEY_POWER);
> +
> + ret = input_register_device(smchid->input);
> + if (ret) {
> + dev_err(&pdev->dev, "Failed to register input device: %d\n", ret);
> + return ret;
> + }
> +
> + if (have_lid) {
> + u8 val;
> +
> + ret = apple_smc_read_u8(smc, SMC_KEY(MSLD), &val);
> + if (ret < 0)
> + dev_warn(&pdev->dev, "Failed to read initial lid state\n");
> + else
> + input_report_switch(smchid->input, SW_LID, val);
> + }
> +
> + if (have_power) {
> + u32 val;
> +
> + ret = apple_smc_read_u32(smc, SMC_KEY(bHLD), &val);
> + if (ret < 0)
> + dev_warn(&pdev->dev, "Failed to read initial power button state\n");
> + else
> + input_report_key(smchid->input, KEY_POWER, val & 1);
> + }
> +
> + input_sync(smchid->input);
> +
> + smchid->nb.notifier_call = macsmc_hid_event;
> + blocking_notifier_chain_register(&smc->event_handlers, &smchid->nb);
> +
> + device_init_wakeup(&pdev->dev, 1);
> +
> + return 0;
> +}
> +
> +static int macsmc_hid_pm_prepare(struct device *dev)
> +{
> + struct macsmc_hid *smchid = dev_get_drvdata(dev);
> +
> + smchid->wakeup_mode = true;
> + return 0;
> +}
> +
> +static void macsmc_hid_pm_complete(struct device *dev)
> +{
> + struct macsmc_hid *smchid = dev_get_drvdata(dev);
> +
> + smchid->wakeup_mode = false;
> +}
> +
> +static const struct dev_pm_ops macsmc_hid_pm_ops = {
> + .prepare = macsmc_hid_pm_prepare,
> + .complete = macsmc_hid_pm_complete,
> +};
> +
> +static struct platform_driver macsmc_hid_driver = {
> + .driver = {
> + .name = "macsmc-hid",
> + .pm = &macsmc_hid_pm_ops,
> + },
> + .probe = macsmc_hid_probe,
> +};
> +module_platform_driver(macsmc_hid_driver);
> +
> +MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
> +MODULE_LICENSE("Dual MIT/GPL");
> +MODULE_DESCRIPTION("Apple SMC HID driver");
> +MODULE_ALIAS("platform:macsmc-hid");

The module alias should be removed.

Janne