[PATCH v6 4/7] input: macsmc-input: New driver to handle the Apple Mac SMC buttons/lid

James Calligeros
2025-12-15T09:38:49Z

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.

Reviewed-by: Neal Gompa <neal@gompa.dev>
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-input.c | 207 +++++++++++++++++++++++++
4 files changed, 220 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 5f160eb6762e..7f2160a18da2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2492,6 +2492,7 @@ 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-input.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 94a753fcb64f..0e805c870e29 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -1003,4 +1003,15 @@ config INPUT_STPMIC1_ONKEY
To compile this driver as a module, choose M here: the
module will be called stpmic1_onkey.

+config INPUT_MACSMC
+ 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-input.
+
endif
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index 415fc4e2918b..174031304975 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -52,6 +52,7 @@ 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-$(CONFIG_INPUT_MACSMC_INPUT) += macsmc-input.o
obj-$(CONFIG_INPUT_MAX7360_ROTARY) += max7360-rotary.o
obj-$(CONFIG_INPUT_MAX77650_ONKEY) += max77650-onkey.o
obj-$(CONFIG_INPUT_MAX77693_HAPTIC) += max77693-haptic.o
diff --git a/drivers/input/misc/macsmc-input.c b/drivers/input/misc/macsmc-input.c
new file mode 100644
index 000000000000..f4598e65fc80
--- /dev/null
+++ b/drivers/input/misc/macsmc-input.c
@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SMC input event driver
+ * Copyright The Asahi Linux Contributors
+ *
+ * This driver exposes certain 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/macsmc.h>
+#include <linux/module.h>
+#include <linux/reboot.h>
+
+/**
+ * struct macsmc_input
+ * @dev: Underlying struct device for the input 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_input {
+ 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_input_event_button(struct macsmc_input *smcin, unsigned long event)
+{
+ u8 button = (event >> 8) & 0xff;
+ u8 state = !!(event & 0xff);
+
+ switch (button) {
+ case BTN_POWER:
+ case BTN_TOUCHID:
+ pm_wakeup_dev_event(smcin->dev, 0, (smcin->wakeup_mode && state));
+
+ /* Suppress KEY_POWER event to prevent immediate shutdown on wake */
+ if (smcin->wakeup_mode)
+ return;
+
+ input_report_key(smcin->input, KEY_POWER, state);
+ input_sync(smcin->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(smcin->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(smcin->dev, "Unknown SMC button event: %04lx\n", event & 0xffff);
+ }
+}
+
+static void macsmc_input_event_lid(struct macsmc_input *smcin, unsigned long event)
+{
+ u8 lid_state = !!((event >> 8) & 0xff);
+
+ pm_wakeup_dev_event(smcin->dev, 0, (smcin->wakeup_mode && !lid_state));
+ input_report_switch(smcin->input, SW_LID, lid_state);
+ input_sync(smcin->input);
+}
+
+static int macsmc_input_event(struct notifier_block *nb, unsigned long event, void *data)
+{
+ struct macsmc_input *smcin = container_of(nb, struct macsmc_input, nb);
+ u16 type = event >> 16;
+
+ switch (type) {
+ case SMC_EV_BTN:
+ macsmc_input_event_button(smcin, event);
+ return NOTIFY_OK;
+ case SMC_EV_LID:
+ macsmc_input_event_lid(smcin, event);
+ return NOTIFY_OK;
+ default:
+ /* SMC event meant for another driver */
+ return NOTIFY_DONE;
+ }
+}
+
+static int macsmc_input_probe(struct platform_device *pdev)
+{
+ struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
+ struct macsmc_input *smcin;
+ bool have_lid, have_power;
+ int error;
+
+ /* 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;
+
+ smcin = devm_kzalloc(&pdev->dev, sizeof(*smcin), GFP_KERNEL);
+ if (!smcin)
+ return -ENOMEM;
+
+ smcin->dev = &pdev->dev;
+ smcin->smc = smc;
+ platform_set_drvdata(pdev, smcin);
+
+ smcin->input = devm_input_allocate_device(&pdev->dev);
+ if (!smcin->input)
+ return -ENOMEM;
+
+ smcin->input->phys = "macsmc-input (0)";
+ smcin->input->name = "Apple SMC power/lid events";
+
+ if (have_lid)
+ input_set_capability(smcin->input, EV_SW, SW_LID);
+ if (have_power)
+ input_set_capability(smcin->input, EV_KEY, KEY_POWER);
+
+ if (have_lid) {
+ u8 val;
+
+ error = apple_smc_read_u8(smc, SMC_KEY(MSLD), &val);
+ if (error < 0)
+ dev_warn(&pdev->dev, "Failed to read initial lid state\n");
+ else
+ input_report_switch(smcin->input, SW_LID, val);
+ }
+
+ if (have_power) {
+ u32 val;
+
+ error = apple_smc_read_u32(smc, SMC_KEY(bHLD), &val);
+ if (error < 0)
+ dev_warn(&pdev->dev, "Failed to read initial power button state\n");
+ else
+ input_report_key(smcin->input, KEY_POWER, val & 1);
+ }
+
+ error = input_register_device(smcin->input);
+ if (error) {
+ dev_err(&pdev->dev, "Failed to register input device: %d\n", error);
+ return error;
+ }
+
+ input_sync(smcin->input);
+
+ smcin->nb.notifier_call = macsmc_input_event;
+ blocking_notifier_chain_register(&smc->event_handlers, &smcin->nb);
+
+ device_init_wakeup(&pdev->dev, true);
+
+ return 0;
+}
+
+static int macsmc_input_pm_prepare(struct device *dev)
+{
+ struct macsmc_input *smcin = dev_get_drvdata(dev);
+
+ smcin->wakeup_mode = true;
+ return 0;
+}
+
+static void macsmc_input_pm_complete(struct device *dev)
+{
+ struct macsmc_input *smcin = dev_get_drvdata(dev);
+
+ smcin->wakeup_mode = false;
+}
+
+static const struct dev_pm_ops macsmc_input_pm_ops = {
+ .prepare = macsmc_input_pm_prepare,
+ .complete = macsmc_input_pm_complete,
+};
+
+static struct platform_driver macsmc_input_driver = {
+ .driver = {
+ .name = "macsmc-input",
+ .pm = &macsmc_input_pm_ops,
+ },
+ .probe = macsmc_input_probe,
+};
+module_platform_driver(macsmc_input_driver);
+
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_DESCRIPTION("Apple SMC input driver");
+MODULE_ALIAS("platform:macsmc-input");

--
2.52.0