[PATCH v2 3/3] iio: light: apple-ib-als: Add driver for ALS on iBridge chip.

["Ronald Tschalär" <ronald@innovation.ch>]

On 2016/2017 MacBook Pro's with a Touch Bar the ALS is attached to,
and exposed via the iBridge device. This provides the driver for that
sensor.

Signed-off-by: Ronald Tschalär <ronald@innovation.ch>
---
 drivers/iio/light/Kconfig        |  12 +
 drivers/iio/light/Makefile       |   1 +
 drivers/iio/light/apple-ib-als.c | 607 +++++++++++++++++++++++++++++++
 3 files changed, 620 insertions(+)
 create mode 100644 drivers/iio/light/apple-ib-als.c

diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
index 5190eacfeb0a..b477aa5d2024 100644
--- a/drivers/iio/light/Kconfig
+++ b/drivers/iio/light/Kconfig
@@ -64,6 +64,18 @@ config APDS9960
 	  To compile this driver as a module, choose M here: the
 	  module will be called apds9960
 
+config APPLE_IBRIDGE_ALS
+	tristate "Apple iBridge ambient light sensor"
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	depends on HID_APPLE_IBRIDGE
+	help
+	  Say Y here to build the driver for the Apple iBridge ALS
+	  sensor.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called apple-ib-als.
+
 config BH1750
 	tristate "ROHM BH1750 ambient light sensor"
 	depends on I2C
diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
index e40794fbb435..cd6cd5ba6da5 100644
--- a/drivers/iio/light/Makefile
+++ b/drivers/iio/light/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_ADJD_S311)		+= adjd_s311.o
 obj-$(CONFIG_AL3320A)		+= al3320a.o
 obj-$(CONFIG_APDS9300)		+= apds9300.o
 obj-$(CONFIG_APDS9960)		+= apds9960.o
+obj-$(CONFIG_APPLE_IBRIDGE_ALS)	+= apple-ib-als.o
 obj-$(CONFIG_BH1750)		+= bh1750.o
 obj-$(CONFIG_BH1780)		+= bh1780.o
 obj-$(CONFIG_CM32181)		+= cm32181.o
diff --git a/drivers/iio/light/apple-ib-als.c b/drivers/iio/light/apple-ib-als.c
new file mode 100644
index 000000000000..b84be0076e0f
--- /dev/null
+++ b/drivers/iio/light/apple-ib-als.c
@@ -0,0 +1,607 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Apple Ambient Light Sensor Driver
+ *
+ * Copyright (c) 2017-2018 Ronald Tschalär
+ */
+
+/*
+ * MacBookPro models with an iBridge chip (13,[23] and 14,[23]) have an
+ * ambient light sensor that is exposed via one of the USB interfaces on
+ * the iBridge as a standard HID light sensor. However, we cannot use the
+ * existing hid-sensor-als driver, for two reasons:
+ *
+ * 1. The hid-sensor-als driver is part of the hid-sensor-hub which in turn
+ *    is a hid driver, but you can't have more than one hid driver per hid
+ *    device, which is a problem because the touch bar also needs to
+ *    register as a driver for this hid device.
+ *
+ * 2. While the hid-sensors-als driver stores sensor readings received via
+ *    interrupt in an iio buffer, reads on the sysfs
+ *    .../iio:deviceX/in_illuminance_YYY attribute result in a get of the
+ *    feature report; however, in the case of this sensor here the
+ *    illuminance field of that report is always 0. Instead, the input
+ *    report needs to be requested.
+ */
+
+#define dev_fmt(fmt) "als: " fmt
+
+#include <linux/apple-ibridge.h>
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/hid-sensor-ids.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/trigger.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#define APPLEALS_DYN_SENS		0	/* our dynamic sensitivity */
+#define APPLEALS_DEF_CHANGE_SENS	APPLEALS_DYN_SENS
+
+struct appleals_device {
+	struct hid_device	*hid_dev;
+	struct hid_report	*cfg_report;
+	struct hid_field	*illum_field;
+	struct iio_dev		*iio_dev;
+	int			cur_sensitivity;
+	int			cur_hysteresis;
+	bool			events_enabled;
+};
+
+static struct hid_driver appleals_hid_driver;
+
+/*
+ * This is a primitive way to get a relative sensitivity, one where we get
+ * notified when the value changes by a certain percentage rather than some
+ * absolute value. MacOS somehow manages to configure the sensor to work this
+ * way (with a 15% relative sensitivity), but I haven't been able to figure
+ * out how so far. So until we do, this provides a less-than-perfect
+ * simulation.
+ *
+ * When the brightness value is within one of the ranges, the sensitivity is
+ * set to that range's sensitivity. But in order to reduce flapping when the
+ * brightness is right on the border between two ranges, the ranges overlap
+ * somewhat (by at least one sensitivity), and sensitivity is only changed if
+ * the value leaves the current sensitivity's range.
+ *
+ * The values chosen for the map are somewhat arbitrary: a compromise of not
+ * too many ranges (and hence changing the sensitivity) but not too small or
+ * large of a percentage of the min and max values in the range (currently
+ * from 7.5% to 30%, i.e. within a factor of 2 of 15%), as well as just plain
+ * "this feels reasonable to me".
+ */
+struct appleals_sensitivity_map {
+	int	sensitivity;
+	int	illum_low;
+	int	illum_high;
+};
+
+static const struct appleals_sensitivity_map appleals_sensitivity_map[] = {
+	{   1,    0,   14 },
+	{   3,   10,   40 },
+	{   9,   30,  120 },
+	{  27,   90,  360 },
+	{  81,  270, 1080 },
+	{ 243,  810, 3240 },
+	{ 729, 2430, 9720 },
+};
+
+static int appleals_compute_sensitivity(int cur_illum, int cur_sens)
+{
+	const struct appleals_sensitivity_map *entry;
+	int i;
+
+	/* see if we're still in current range */
+	for (i = 0; i < ARRAY_SIZE(appleals_sensitivity_map); i++) {
+		entry = &appleals_sensitivity_map[i];
+
+		if (entry->sensitivity == cur_sens &&
+		    entry->illum_low <= cur_illum &&
+		    entry->illum_high >= cur_illum)
+			return cur_sens;
+		else if (entry->sensitivity > cur_sens)
+			break;
+	}
+
+	/* not in current range, so find new sensitivity */
+	for (i = 0; i < ARRAY_SIZE(appleals_sensitivity_map); i++) {
+		entry = &appleals_sensitivity_map[i];
+
+		if (entry->illum_low <= cur_illum &&
+		    entry->illum_high >= cur_illum)
+			return entry->sensitivity;
+	}
+
+	/* hmm, not in table, so assume we are above highest range */
+	i = ARRAY_SIZE(appleals_sensitivity_map) - 1;
+	return appleals_sensitivity_map[i].sensitivity;
+}
+
+static int appleals_get_field_value_for_usage(struct hid_field *field,
+					      unsigned int usage)
+{
+	int u;
+
+	if (!field)
+		return -1;
+
+	for (u = 0; u < field->maxusage; u++) {
+		if (field->usage[u].hid == usage)
+			return u + field->logical_minimum;
+	}
+
+	return -1;
+}
+
+static __s32 appleals_get_field_value(struct appleals_device *als_dev,
+				      struct hid_field *field)
+{
+	bool powered_on = !hid_hw_power(als_dev->hid_dev, PM_HINT_FULLON);
+
+	hid_hw_request(als_dev->hid_dev, field->report, HID_REQ_GET_REPORT);
+	hid_hw_wait(als_dev->hid_dev);
+
+	if (powered_on)
+		hid_hw_power(als_dev->hid_dev, PM_HINT_NORMAL);
+
+	return field->value[0];
+}
+
+static void appleals_set_field_value(struct appleals_device *als_dev,
+				     struct hid_field *field, __s32 value)
+{
+	hid_set_field(field, 0, value);
+	hid_hw_request(als_dev->hid_dev, field->report, HID_REQ_SET_REPORT);
+}
+
+static int appleals_get_config(struct appleals_device *als_dev,
+			       unsigned int field_usage, __s32 *value)
+{
+	struct hid_field *field;
+
+	field = appleib_find_report_field(als_dev->cfg_report, field_usage);
+	if (!field)
+		return -EINVAL;
+
+	*value = appleals_get_field_value(als_dev, field);
+
+	return 0;
+}
+
+static int appleals_set_config(struct appleals_device *als_dev,
+			       unsigned int field_usage, __s32 value)
+{
+	struct hid_field *field;
+
+	field = appleib_find_report_field(als_dev->cfg_report, field_usage);
+	if (!field)
+		return -EINVAL;
+
+	appleals_set_field_value(als_dev, field, value);
+
+	return 0;
+}
+
+static int appleals_set_enum_config(struct appleals_device *als_dev,
+				    unsigned int field_usage,
+				    unsigned int value_usage)
+{
+	struct hid_field *field;
+	int value;
+
+	field = appleib_find_report_field(als_dev->cfg_report, field_usage);
+	if (!field)
+		return -EINVAL;
+
+	value = appleals_get_field_value_for_usage(field, value_usage);
+	if (value >= 0)
+		appleals_set_field_value(als_dev, field, value);
+
+	return 0;
+}
+
+static void appleals_update_dyn_sensitivity(struct appleals_device *als_dev,
+					    __s32 value)
+{
+	int new_sens;
+	int rc;
+
+	new_sens = appleals_compute_sensitivity(value,
+						als_dev->cur_sensitivity);
+	if (new_sens != als_dev->cur_sensitivity) {
+		rc = appleals_set_config(als_dev,
+			HID_USAGE_SENSOR_LIGHT_ILLUM |
+			HID_USAGE_SENSOR_DATA_MOD_CHANGE_SENSITIVITY_ABS,
+			new_sens);
+		if (!rc)
+			als_dev->cur_sensitivity = new_sens;
+	}
+}
+
+static void appleals_push_new_value(struct appleals_device *als_dev,
+				    __s32 value)
+{
+	__s32 buf[2] = { value, value };
+
+	iio_push_to_buffers(als_dev->iio_dev, buf);
+
+	if (als_dev->cur_hysteresis == APPLEALS_DYN_SENS)
+		appleals_update_dyn_sensitivity(als_dev, value);
+}
+
+static int appleals_hid_event(struct hid_device *hdev, struct hid_field *field,
+			      struct hid_usage *usage, __s32 value)
+{
+	struct appleals_device *als_dev = hid_get_drvdata(hdev);
+	int rc = 0;
+
+	if ((usage->hid & HID_USAGE_PAGE) != HID_UP_SENSOR)
+		return 0;
+
+	if (usage->hid == HID_USAGE_SENSOR_LIGHT_ILLUM) {
+		appleals_push_new_value(als_dev, value);
+		rc = 1;
+	}
+
+	return rc;
+}
+
+static int appleals_enable_events(struct iio_trigger *trig, bool enable)
+{
+	struct appleals_device *als_dev = iio_trigger_get_drvdata(trig);
+	int value;
+
+	appleals_set_enum_config(als_dev, HID_USAGE_SENSOR_PROP_REPORT_STATE,
+		enable ? HID_USAGE_SENSOR_PROP_REPORTING_STATE_ALL_EVENTS_ENUM :
+			 HID_USAGE_SENSOR_PROP_REPORTING_STATE_NO_EVENTS_ENUM);
+	als_dev->events_enabled = enable;
+
+	/* if the sensor was enabled, push an initial value */
+	if (enable) {
+		value = appleals_get_field_value(als_dev, als_dev->illum_field);
+		appleals_push_new_value(als_dev, value);
+	}
+
+	return 0;
+}
+
+static int appleals_read_raw(struct iio_dev *iio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct appleals_device **priv = iio_priv(iio_dev);
+	struct appleals_device *als_dev = *priv;
+	__s32 value;
+	int rc;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		*val = appleals_get_field_value(als_dev, als_dev->illum_field);
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		rc = appleals_get_config(als_dev,
+					 HID_USAGE_SENSOR_PROP_REPORT_INTERVAL,
+					 &value);
+		if (rc)
+			return rc;
+
+		/* interval is in ms; val is in HZ, val2 in µHZ */
+		value = 1000000000 / value;
+		*val = value / 1000000;
+		*val2 = value - (*val * 1000000);
+
+		return IIO_VAL_INT_PLUS_MICRO;
+
+	case IIO_CHAN_INFO_HYSTERESIS:
+		if (als_dev->cur_hysteresis == APPLEALS_DYN_SENS) {
+			*val = als_dev->cur_hysteresis;
+			return IIO_VAL_INT;
+		}
+
+		rc = appleals_get_config(als_dev,
+			HID_USAGE_SENSOR_LIGHT_ILLUM |
+			HID_USAGE_SENSOR_DATA_MOD_CHANGE_SENSITIVITY_ABS,
+			val);
+		if (!rc) {
+			als_dev->cur_sensitivity = *val;
+			als_dev->cur_hysteresis = *val;
+		}
+		return rc ? rc : IIO_VAL_INT;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int appleals_write_raw(struct iio_dev *iio_dev,
+			      struct iio_chan_spec const *chan,
+			      int val, int val2, long mask)
+{
+	struct appleals_device **priv = iio_priv(iio_dev);
+	struct appleals_device *als_dev = *priv;
+	__s32 illum;
+	int rc;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		rc = appleals_set_config(als_dev,
+					 HID_USAGE_SENSOR_PROP_REPORT_INTERVAL,
+					 1000000000 / (val * 1000000 + val2));
+		return rc;
+
+	case IIO_CHAN_INFO_HYSTERESIS:
+		if (val == APPLEALS_DYN_SENS) {
+			if (als_dev->cur_hysteresis != APPLEALS_DYN_SENS) {
+				als_dev->cur_hysteresis = val;
+				illum = appleals_get_field_value(als_dev,
+							als_dev->illum_field);
+				appleals_update_dyn_sensitivity(als_dev, illum);
+			}
+
+			return 0;
+		}
+
+		rc = appleals_set_config(als_dev,
+			HID_USAGE_SENSOR_LIGHT_ILLUM |
+			HID_USAGE_SENSOR_DATA_MOD_CHANGE_SENSITIVITY_ABS,
+			val);
+		if (!rc) {
+			als_dev->cur_sensitivity = val;
+			als_dev->cur_hysteresis = val;
+		}
+
+		return rc;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_chan_spec appleals_channels[] = {
+	{
+		.type = IIO_INTENSITY,
+		.modified = 1,
+		.channel2 = IIO_MOD_LIGHT_BOTH,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ) |
+			BIT(IIO_CHAN_INFO_HYSTERESIS),
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 32,
+			.storagebits = 32,
+		},
+		.scan_index = 0,
+	},
+	{
+		.type = IIO_LIGHT,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ) |
+			BIT(IIO_CHAN_INFO_HYSTERESIS),
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 32,
+			.storagebits = 32,
+		},
+		.scan_index = 1,
+	}
+};
+
+static const struct iio_trigger_ops appleals_trigger_ops = {
+	.set_trigger_state = &appleals_enable_events,
+};
+
+static const struct iio_info appleals_info = {
+	.read_raw = &appleals_read_raw,
+	.write_raw = &appleals_write_raw,
+};
+
+static void appleals_config_sensor(struct appleals_device *als_dev,
+				   bool events_enabled, int sensitivity)
+{
+	struct hid_field *field;
+	bool powered_on;
+	__s32 val;
+
+	powered_on = !hid_hw_power(als_dev->hid_dev, PM_HINT_FULLON);
+
+	hid_hw_request(als_dev->hid_dev, als_dev->cfg_report,
+		       HID_REQ_GET_REPORT);
+	hid_hw_wait(als_dev->hid_dev);
+
+	field = appleib_find_report_field(als_dev->cfg_report,
+					  HID_USAGE_SENSOR_PROY_POWER_STATE);
+	val = appleals_get_field_value_for_usage(field,
+			HID_USAGE_SENSOR_PROP_POWER_STATE_D0_FULL_POWER_ENUM);
+	if (val >= 0)
+		hid_set_field(field, 0, val);
+
+	field = appleib_find_report_field(als_dev->cfg_report,
+					  HID_USAGE_SENSOR_PROP_REPORT_STATE);
+	val = appleals_get_field_value_for_usage(field,
+		events_enabled ?
+			HID_USAGE_SENSOR_PROP_REPORTING_STATE_ALL_EVENTS_ENUM :
+			HID_USAGE_SENSOR_PROP_REPORTING_STATE_NO_EVENTS_ENUM);
+	if (val >= 0)
+		hid_set_field(field, 0, val);
+
+	field = appleib_find_report_field(als_dev->cfg_report,
+					 HID_USAGE_SENSOR_PROP_REPORT_INTERVAL);
+	hid_set_field(field, 0, field->logical_minimum);
+
+	/*
+	 * Set initial change sensitivity; if dynamic, enabling trigger will set
+	 * it instead.
+	 */
+	if (sensitivity != APPLEALS_DYN_SENS) {
+		field = appleib_find_report_field(als_dev->cfg_report,
+			HID_USAGE_SENSOR_LIGHT_ILLUM |
+			HID_USAGE_SENSOR_DATA_MOD_CHANGE_SENSITIVITY_ABS);
+
+		hid_set_field(field, 0, sensitivity);
+	}
+
+	hid_hw_request(als_dev->hid_dev, als_dev->cfg_report,
+		       HID_REQ_SET_REPORT);
+
+	if (powered_on)
+		hid_hw_power(als_dev->hid_dev, PM_HINT_NORMAL);
+}
+
+static int appleals_config_iio(struct appleals_device *als_dev)
+{
+	struct iio_dev *iio_dev;
+	struct iio_trigger *iio_trig;
+	struct appleals_device **priv;
+	struct device *parent = &als_dev->hid_dev->dev;
+	int rc;
+
+	iio_dev = devm_iio_device_alloc(parent, sizeof(als_dev));
+	if (!iio_dev)
+		return -ENOMEM;
+
+	priv = iio_priv(iio_dev);
+	*priv = als_dev;
+
+	iio_dev->channels = appleals_channels;
+	iio_dev->num_channels = ARRAY_SIZE(appleals_channels);
+	iio_dev->dev.parent = parent;
+	iio_dev->info = &appleals_info;
+	iio_dev->name = "als";
+	iio_dev->modes = INDIO_DIRECT_MODE;
+
+	rc = devm_iio_triggered_buffer_setup(parent, iio_dev,
+					     &iio_pollfunc_store_time, NULL,
+					     NULL);
+	if (rc) {
+		hid_err(als_dev->hid_dev,
+			"Failed to set up iio triggered buffer: %d\n", rc);
+		return rc;
+	}
+
+	iio_trig = devm_iio_trigger_alloc(parent, "%s-dev%d", iio_dev->name,
+					  iio_dev->id);
+	if (!iio_trig)
+		return -ENOMEM;
+
+	iio_trig->dev.parent = parent;
+	iio_trig->ops = &appleals_trigger_ops;
+	iio_trigger_set_drvdata(iio_trig, als_dev);
+
+	rc = devm_iio_trigger_register(parent, iio_trig);
+	if (rc) {
+		hid_err(als_dev->hid_dev,
+			"Failed to register iio trigger: %d\n",
+			rc);
+		return rc;
+	}
+
+	rc = devm_iio_device_register(parent, iio_dev);
+	if (rc) {
+		hid_err(als_dev->hid_dev, "Failed to register iio device: %d\n",
+			rc);
+		return rc;
+	}
+
+	als_dev->iio_dev = iio_dev;
+
+	return 0;
+}
+
+static int appleals_probe(struct hid_device *hdev,
+			  const struct hid_device_id *id)
+{
+	struct appleals_device *als_dev;
+	struct hid_field *state_field;
+	struct hid_field *illum_field;
+	int rc;
+
+	/* find als fields and reports */
+	rc = hid_parse(hdev);
+	if (rc) {
+		hid_err(hdev, "als: hid parse failed (%d)\n", rc);
+		return rc;
+	}
+
+	state_field = appleib_find_hid_field(hdev, HID_USAGE_SENSOR_ALS,
+					    HID_USAGE_SENSOR_PROP_REPORT_STATE);
+	illum_field = appleib_find_hid_field(hdev, HID_USAGE_SENSOR_ALS,
+					     HID_USAGE_SENSOR_LIGHT_ILLUM);
+	if (!state_field || !illum_field)
+		return -ENODEV;
+
+	hid_dbg(hdev, "Found ambient light sensor\n");
+
+	/* initialize device */
+	als_dev = devm_kzalloc(&hdev->dev, sizeof(*als_dev), GFP_KERNEL);
+	if (!als_dev)
+		return -ENOMEM;
+
+	als_dev->hid_dev = hdev;
+	als_dev->cfg_report = state_field->report;
+	als_dev->illum_field = illum_field;
+
+	als_dev->cur_hysteresis = APPLEALS_DEF_CHANGE_SENS;
+	als_dev->cur_sensitivity = APPLEALS_DEF_CHANGE_SENS;
+
+	hid_set_drvdata(hdev, als_dev);
+
+	rc = hid_hw_start(hdev, HID_CONNECT_DRIVER);
+	if (rc) {
+		hid_err(hdev, "als: hw start failed (%d)\n", rc);
+		return rc;
+	}
+
+	hid_device_io_start(hdev);
+	appleals_config_sensor(als_dev, false, als_dev->cur_sensitivity);
+	hid_device_io_stop(hdev);
+
+	rc = appleals_config_iio(als_dev);
+	if (rc)
+		return rc;
+
+	return hid_hw_open(hdev);
+}
+
+#ifdef CONFIG_PM
+static int appleals_reset_resume(struct hid_device *hdev)
+{
+	struct appleals_device *als_dev = hid_get_drvdata(hdev);
+	__s32 illum;
+
+	appleals_config_sensor(als_dev, als_dev->events_enabled,
+			       als_dev->cur_sensitivity);
+
+	illum = appleals_get_field_value(als_dev, als_dev->illum_field);
+	appleals_push_new_value(als_dev, illum);
+
+	return 0;
+}
+#endif
+
+static const struct hid_device_id appleals_hid_ids[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LINUX_FOUNDATION,
+			 USB_DEVICE_ID_IBRIDGE_ALS) },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(hid, appleals_hid_ids);
+
+static struct hid_driver appleals_hid_driver = {
+	.name = "apple-ib-als",
+	.id_table = appleals_hid_ids,
+	.probe = appleals_probe,
+	.event = appleals_hid_event,
+#ifdef CONFIG_PM
+	.reset_resume = appleals_reset_resume,
+#endif
+};
+
+module_hid_driver(appleals_hid_driver);
+
+MODULE_AUTHOR("Ronald Tschalär");
+MODULE_DESCRIPTION("Apple iBridge ALS driver");
+MODULE_LICENSE("GPL v2");
-- 
2.21.0