[RFC PATCH 04/14] iio/light: add new driver for macsmc

[Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>]

Add a driver for the ambient light sensors, exposed through
the standard IIO interface with left and right channels.

This replaces the light sensor support in applesmc.

Signed-off-by: Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>
---
 drivers/iio/light/Kconfig        |  11 ++
 drivers/iio/light/Makefile       |   1 +
 drivers/iio/light/macsmc-light.c | 189 +++++++++++++++++++++++++++++++
 drivers/mfd/macsmc-core.c        |  11 ++
 4 files changed, 212 insertions(+)
 create mode 100644 drivers/iio/light/macsmc-light.c

diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
index 462fff1dd..f84707edc 100644
--- a/drivers/iio/light/Kconfig
+++ b/drivers/iio/light/Kconfig
@@ -457,6 +457,17 @@ config LV0104CS
 	  To compile this driver as a module, choose M here:
 	  the module will be called lv0104cs.
 
+config MACSMC_LIGHT
+	tristate "Apple SMC Light Sensor"
+	depends on MACSMC_ACPI
+	help
+	  Say Y here if you have a Intel-based Mac. and you
+	  want support for light sensors.
+
+	  To compile this driver as a module, choose M here:
+	  the module will be called macsmc_light
+
+
 config MAX44000
 	tristate "MAX44000 Ambient and Infrared Proximity Sensor"
 	depends on I2C
diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
index 6672ed01a..2ef4c054d 100644
--- a/drivers/iio/light/Makefile
+++ b/drivers/iio/light/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_LTR390)		+= ltr390.o
 obj-$(CONFIG_LTR501)		+= ltr501.o
 obj-$(CONFIG_LTRF216A)		+= ltrf216a.o
 obj-$(CONFIG_LV0104CS)		+= lv0104cs.o
+obj-$(CONFIG_MACSMC_LIGHT)	+= macsmc-light.o
 obj-$(CONFIG_MAX44000)		+= max44000.o
 obj-$(CONFIG_MAX44009)		+= max44009.o
 obj-$(CONFIG_NOA1305)		+= noa1305.o
diff --git a/drivers/iio/light/macsmc-light.c b/drivers/iio/light/macsmc-light.c
new file mode 100644
index 000000000..9d4532b34
--- /dev/null
+++ b/drivers/iio/light/macsmc-light.c
@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Apple SMC Light Sensor Driver
+ *
+ * Copyright (C) 2026 Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>
+ *
+ * Based on drivers/hwmom/applesmc.c:
+ * Copyright (C) 2007 Nicolas Boichat <nicolas@boichat.ch>
+ * Copyright (C) 2010 Henrik Rydberg <rydberg@euromail.se>
+ */
+
+#include <linux/iio/events.h>
+#include <linux/iio/iio.h>
+#include <linux/byteorder/generic.h>
+#include <linux/mfd/macsmc.h>
+#include <linux/platform_device.h>
+#include <linux/unaligned.h>
+
+enum {
+	LEFT_LIGHT = 0,
+	RIGHT_LIGHT
+};
+
+struct macsmc_light {
+	struct apple_smc *smc;
+	struct notifier_block nb;
+	struct iio_dev *indio_dev;
+	u8 size;
+};
+
+static int macsmc_light_read_raw(struct iio_dev *indio_dev,
+		const struct iio_chan_spec *chan,
+		int *val, int *val2, long mask)
+
+{
+	struct macsmc_light *drv = iio_priv(indio_dev);
+	u8 buffer[10];
+	int ret;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	switch (chan->channel) {
+	case LEFT_LIGHT:
+		ret = apple_smc_read(drv->smc, SMC_KEY(ALV0), buffer, drv->size);
+		if (ret < 0)
+			return ret;
+
+		if (drv->size == 10)
+			*val = be16_to_cpu(get_unaligned_be16(buffer + 6)) >> 10;
+		else
+			*val = buffer[2];
+
+		break;
+	case RIGHT_LIGHT:
+		if (drv->size == 10) {
+			*val = 0;
+			break;
+		}
+		ret = apple_smc_read(drv->smc, SMC_KEY(ALV1), buffer, drv->size);
+		if (ret < 0)
+			return ret;
+
+		*val = buffer[2];
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return IIO_VAL_INT;
+}
+
+static int macsmc_light_event(struct notifier_block *nb, unsigned long event, void *data)
+{
+	struct macsmc_light *drv = container_of(nb, struct macsmc_light, nb);
+	s64 timestamp = iio_get_time_ns(drv->indio_dev);
+
+	/* check if event is for us */
+	if (event != 0x2A)
+		return NOTIFY_DONE;
+
+	iio_push_event(drv->indio_dev,
+		IIO_UNMOD_EVENT_CODE(IIO_LIGHT,
+				LEFT_LIGHT,
+				IIO_EV_TYPE_CHANGE,
+				IIO_EV_DIR_EITHER),
+		timestamp);
+
+	if (drv->size != 10) {
+		iio_push_event(drv->indio_dev,
+			IIO_UNMOD_EVENT_CODE(IIO_LIGHT,
+					RIGHT_LIGHT,
+					IIO_EV_TYPE_CHANGE,
+					IIO_EV_DIR_EITHER),
+				timestamp);
+	}
+
+	return NOTIFY_OK;
+}
+
+static void macsmc_light_unregister_notifier(void *data)
+{
+	struct macsmc_light *drv = data;
+
+	blocking_notifier_chain_unregister(drv->smc->event_handlers,
+					   &drv->nb);
+}
+
+static const struct iio_event_spec macsmc_light_events[] = {
+	{
+		.type = IIO_EV_TYPE_CHANGE,
+		.dir = IIO_EV_DIR_EITHER,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+static const struct iio_chan_spec macsmc_light_channels[] = {
+	{
+		.type = IIO_LIGHT,
+		.channel = LEFT_LIGHT,
+		.extend_name = "left",
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.event_spec = macsmc_light_events,
+		.num_event_specs = ARRAY_SIZE(macsmc_light_events),
+	},
+	{
+		.type = IIO_LIGHT,
+		.channel = RIGHT_LIGHT,
+		.extend_name = "right",
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.event_spec = macsmc_light_events,
+		.num_event_specs = ARRAY_SIZE(macsmc_light_events),
+	},
+};
+
+static const struct iio_info macsmc_light_info = {
+	.read_raw = macsmc_light_read_raw,
+};
+
+static int macsmc_light_probe(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev;
+	struct macsmc_light *drv;
+	struct apple_smc_key_info info;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*drv));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	drv = iio_priv(indio_dev);
+	drv->smc = dev_get_drvdata(pdev->dev.parent);
+
+	ret = apple_smc_get_key_info(drv->smc, SMC_KEY(ALV0), &info);
+	if (ret < 0)
+		return -ENODEV;
+
+	drv->size = info.size;
+	drv->indio_dev = indio_dev;
+	drv->nb.notifier_call = macsmc_light_event;
+	ret = blocking_notifier_chain_register(drv->smc->event_handlers, &drv->nb);
+	if (ret)
+		return ret;
+
+	ret = devm_add_action_or_reset(&pdev->dev, macsmc_light_unregister_notifier, drv);
+	if (ret)
+		return ret;
+
+	indio_dev->name = "macsmc-light";
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &macsmc_light_info;
+	indio_dev->channels = macsmc_light_channels;
+	indio_dev->num_channels = ARRAY_SIZE(macsmc_light_channels);
+
+	return devm_iio_device_register(&pdev->dev, indio_dev);
+}
+
+static struct platform_driver macsmc_light_driver = {
+	.probe = macsmc_light_probe,
+	.driver = {
+		.name = "macsmc-light",
+	},
+};
+module_platform_driver(macsmc_light_driver);
+
+MODULE_AUTHOR("Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_DESCRIPTION("Apple SMC Light Sensor Driver");
+MODULE_ALIAS("platform:macsmc-light");
diff --git a/drivers/mfd/macsmc-core.c b/drivers/mfd/macsmc-core.c
index 1c1469828..6014df4fe 100644
--- a/drivers/mfd/macsmc-core.c
+++ b/drivers/mfd/macsmc-core.c
@@ -29,6 +29,10 @@ static const struct mfd_cell apple_smc_acpi_common[] = {
 	MFD_CELL_NAME("macsmc-power"),
 };
 
+static const struct mfd_cell apple_smc_acpi_light[] = {
+	MFD_CELL_NAME("macsmc-light"),
+};
+
 static const struct mfd_cell apple_smc_acpi_rtc[] = {
 	MFD_CELL_NAME("macsmc-rtc"),
 };
@@ -158,6 +162,13 @@ int apple_smc_probe(struct device *dev, const struct apple_smc_backend_ops *ops,
 				return ret;
 		}
 
+		if (apple_smc_key_exists(smc, SMC_KEY(ALV0))) {
+			ret = devm_mfd_add_devices(dev, -1, apple_smc_acpi_light,
+				ARRAY_SIZE(apple_smc_acpi_light), NULL, 0, NULL);
+			if (ret < 0)
+				return ret;
+		}
+
 	} else
 		ret = devm_mfd_add_devices(dev, -1, apple_smc_rtkit_devs,
 			ARRAY_SIZE(apple_smc_rtkit_devs), NULL, 0, NULL);
-- 
2.55.0