Input: macsmc-hid: New driver to handle the Apple Mac SMC buttons/lid

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>

drivers/input/misc/Kconfig

@@ -892,4 +892,16 @@ 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 APPLE_SMC
+	default ARCH_APPLE
+	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

drivers/input/misc/Makefile

@@ -47,6 +47,7 @@ obj-$(CONFIG_INPUT_IQS626A)		+= iqs626a.o
 obj-$(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

drivers/input/misc/macsmc-hid.c

@@ -0,0 +1,157 @@
+// 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/reboot.h>
+
+struct macsmc_hid {
+	struct device *dev;
+	struct apple_smc *smc;
+	struct input_dev *input;
+	struct notifier_block nb;
+};
+
+#define SMC_EV_BTN 0x7201
+#define SMC_EV_LID 0x7203
+
+#define BTN_POWER	0x06
+#define BTN_POWER_HELD1	0xfe
+#define BTN_POWER_HELD2	0x00
+
+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;
+	u8 d1 = (event >> 8) & 0xff;
+	u8 d2 = event & 0xff;
+
+	switch (type) {
+	case SMC_EV_BTN:
+		switch (d1) {
+		case BTN_POWER:
+			input_report_key(smchid->input, KEY_POWER, d2);
+			input_sync(smchid->input);
+			break;
+		case BTN_POWER_HELD1:
+			/*
+			 * TODO: is this pre-warning useful?
+			 */
+			if (d2)
+				dev_warn(smchid->dev, "Power button held down\n");
+			break;
+		case BTN_POWER_HELD2:
+			/*
+			 * If we get here, we have about 4 seconds before forced shutdown.
+			 * Try to do an emergency shutdown to make sure the NVMe cache is
+			 * flushed. macOS actually does this by panicing (!)...
+			 */
+			if (d2) {
+				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_info(smchid->dev, "Unknown SMC button event: %02x %02x\n", d1, d2);
+			break;
+		}
+		return NOTIFY_OK;
+	case SMC_EV_LID:
+		input_report_switch(smchid->input, SW_LID, d1);
+		input_sync(smchid->input);
+		return NOTIFY_OK;
+	}
+
+	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;
+
+	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;
+
+	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_err(&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_err(&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;
+	apple_smc_register_notifier(smc, &smchid->nb);
+
+	return 0;
+}
+
+static struct platform_driver macsmc_hid_driver = {
+	.driver = {
+		.name = "macsmc-hid",
+	},
+	.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 GPIO driver");
+MODULE_ALIAS("platform:macsmc-hid");