iio: acpi: Add support for ACPI0008 Ambient Light Sensor

This driver adds the initial support for the ACPI Ambient Light Sensor
as defined in Section 9.2 of the ACPI specification (Revision 5.0) [1].

Sensors complying with the standard are exposed as ACPI devices with
ACPI0008 as hardware ID and provide standard methods by which the OS
can query properties of the ambient light environment the system is
currently operating in.

This driver currently allows only to get the current ambient light
illuminance reading through the _ALI method, but is ready to be
extended extended to handle _ALC, _ALT and _ALP as well.

[1] http://www.acpi.info/DOWNLOADS/ACPIspec50.pdf

Signed-off-by: Martin Liska <marxin.liska@gmail.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/Kconfig

@@ -5,6 +5,19 @@
 
 menu "Light sensors"
 
+config ACPI_ALS
+	tristate "ACPI Ambient Light Sensor"
+	depends on ACPI
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	select IIO_KFIFO_BUF
+	help
+	 Say Y here if you want to build a driver for the ACPI0008
+	 Ambient Light Sensor.
+
+	 To compile this driver as a module, choose M here: the module will
+	 be called acpi-als.
+
 config ADJD_S311
 	tristate "ADJD-S311-CR999 digital color sensor"
 	select IIO_BUFFER

drivers/iio/light/Makefile

@@ -3,6 +3,7 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_ACPI_ALS)		+= acpi-als.o
 obj-$(CONFIG_ADJD_S311)		+= adjd_s311.o
 obj-$(CONFIG_AL3320A)		+= al3320a.o
 obj-$(CONFIG_APDS9300)		+= apds9300.o

drivers/iio/light/acpi-als.c

@@ -0,0 +1,231 @@
+/*
+ * ACPI Ambient Light Sensor Driver
+ *
+ * Based on ALS driver:
+ * Copyright (C) 2009 Zhang Rui <rui.zhang@intel.com>
+ *
+ * Rework for IIO subsystem:
+ * Copyright (C) 2012-2013 Martin Liska <marxin.liska@gmail.com>
+ *
+ * Final cleanup and debugging:
+ * Copyright (C) 2013-2014 Marek Vasut <marex@denx.de>
+ * Copyright (C) 2015 Gabriele Mazzotta <gabriele.mzt@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+#include <linux/module.h>
+#include <linux/acpi.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/kfifo_buf.h>
+
+#define ACPI_ALS_CLASS			"als"
+#define ACPI_ALS_DEVICE_NAME		"acpi-als"
+#define ACPI_ALS_NOTIFY_ILLUMINANCE	0x80
+
+ACPI_MODULE_NAME("acpi-als");
+
+/*
+ * So far, there's only one channel in here, but the specification for
+ * ACPI0008 says there can be more to what the block can report. Like
+ * chromaticity and such. We are ready for incoming additions!
+ */
+static const struct iio_chan_spec acpi_als_channels[] = {
+	{
+		.type		= IIO_LIGHT,
+		.scan_type	= {
+			.sign		= 's',
+			.realbits	= 32,
+			.storagebits	= 32,
+		},
+		.info_mask_separate	= BIT(IIO_CHAN_INFO_RAW),
+	},
+};
+
+/*
+ * The event buffer contains timestamp and all the data from
+ * the ACPI0008 block. There are multiple, but so far we only
+ * support _ALI (illuminance). Once someone adds new channels
+ * to acpi_als_channels[], the evt_buffer below will grow
+ * automatically.
+ */
+#define EVT_NR_SOURCES		ARRAY_SIZE(acpi_als_channels)
+#define EVT_BUFFER_SIZE		\
+	(sizeof(s64) + (EVT_NR_SOURCES * sizeof(s32)))
+
+struct acpi_als {
+	struct acpi_device	*device;
+	struct mutex		lock;
+
+	s32			evt_buffer[EVT_BUFFER_SIZE];
+};
+
+/*
+ * All types of properties the ACPI0008 block can report. The ALI, ALC, ALT
+ * and ALP can all be handled by als_read_value() below, while the ALR is
+ * special.
+ *
+ * The _ALR property returns tables that can be used to fine-tune the values
+ * reported by the other props based on the particular hardware type and it's
+ * location (it contains tables for "rainy", "bright inhouse lighting" etc.).
+ *
+ * So far, we support only ALI (illuminance).
+ */
+#define ACPI_ALS_ILLUMINANCE	"_ALI"
+#define ACPI_ALS_CHROMATICITY	"_ALC"
+#define ACPI_ALS_COLOR_TEMP	"_ALT"
+#define ACPI_ALS_POLLING	"_ALP"
+#define ACPI_ALS_TABLES		"_ALR"
+
+static int als_read_value(struct acpi_als *als, char *prop, s32 *val)
+{
+	unsigned long long temp_val;
+	acpi_status status;
+
+	status = acpi_evaluate_integer(als->device->handle, prop, NULL,
+				       &temp_val);
+
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Error reading ALS %s", prop));
+		return -EIO;
+	}
+
+	*val = temp_val;
+
+	return 0;
+}
+
+static void acpi_als_notify(struct acpi_device *device, u32 event)
+{
+	struct iio_dev *indio_dev = acpi_driver_data(device);
+	struct acpi_als *als = iio_priv(indio_dev);
+	s32 *buffer = als->evt_buffer;
+	s64 time_ns = iio_get_time_ns();
+	s32 val;
+	int ret;
+
+	mutex_lock(&als->lock);
+
+	memset(buffer, 0, EVT_BUFFER_SIZE);
+
+	switch (event) {
+	case ACPI_ALS_NOTIFY_ILLUMINANCE:
+		ret = als_read_value(als, ACPI_ALS_ILLUMINANCE, &val);
+		if (ret < 0)
+			goto out;
+		*buffer++ = val;
+		break;
+	default:
+		/* Unhandled event */
+		dev_dbg(&device->dev, "Unhandled ACPI ALS event (%08x)!\n",
+			event);
+		goto out;
+	}
+
+	iio_push_to_buffers_with_timestamp(indio_dev, als->evt_buffer, time_ns);
+
+out:
+	mutex_unlock(&als->lock);
+}
+
+static int acpi_als_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, int *val,
+			     int *val2, long mask)
+{
+	struct acpi_als *als = iio_priv(indio_dev);
+	s32 temp_val;
+	int ret;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	/* we support only illumination (_ALI) so far. */
+	if (chan->type != IIO_LIGHT)
+		return -EINVAL;
+
+	ret = als_read_value(als, ACPI_ALS_ILLUMINANCE, &temp_val);
+	if (ret < 0)
+		return ret;
+
+	*val = temp_val;
+
+	return IIO_VAL_INT;
+}
+
+static const struct iio_info acpi_als_info = {
+	.driver_module		= THIS_MODULE,
+	.read_raw		= acpi_als_read_raw,
+};
+
+static int acpi_als_add(struct acpi_device *device)
+{
+	struct acpi_als *als;
+	struct iio_dev *indio_dev;
+	struct iio_buffer *buffer;
+
+	indio_dev = devm_iio_device_alloc(&device->dev, sizeof(*als));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	als = iio_priv(indio_dev);
+
+	device->driver_data = indio_dev;
+	als->device = device;
+	mutex_init(&als->lock);
+
+	indio_dev->name = ACPI_ALS_DEVICE_NAME;
+	indio_dev->dev.parent = &device->dev;
+	indio_dev->info = &acpi_als_info;
+	indio_dev->modes = INDIO_BUFFER_SOFTWARE;
+	indio_dev->channels = acpi_als_channels;
+	indio_dev->num_channels = ARRAY_SIZE(acpi_als_channels);
+
+	buffer = devm_iio_kfifo_allocate(&device->dev);
+	if (!buffer)
+		return -ENOMEM;
+
+	iio_device_attach_buffer(indio_dev, buffer);
+
+	return devm_iio_device_register(&device->dev, indio_dev);
+}
+
+static const struct acpi_device_id acpi_als_device_ids[] = {
+	{"ACPI0008", 0},
+	{},
+};
+
+MODULE_DEVICE_TABLE(acpi, acpi_als_device_ids);
+
+static struct acpi_driver acpi_als_driver = {
+	.name	= "acpi_als",
+	.class	= ACPI_ALS_CLASS,
+	.ids	= acpi_als_device_ids,
+	.ops = {
+		.add	= acpi_als_add,
+		.notify	= acpi_als_notify,
+	},
+};
+
+module_acpi_driver(acpi_als_driver);
+
+MODULE_AUTHOR("Zhang Rui <rui.zhang@intel.com>");
+MODULE_AUTHOR("Martin Liska <marxin.liska@gmail.com>");
+MODULE_AUTHOR("Marek Vasut <marex@denx.de>");
+MODULE_DESCRIPTION("ACPI Ambient Light Sensor Driver");
+MODULE_LICENSE("GPL");