platform/x86: Add ACPI i2c-multi-instantiate pseudo driver

On systems with ACPI instantiated i2c-clients, normally there is 1 fw_node
per i2c-device and that fw-node contains 1 I2cSerialBus resource for that 1
i2c-device.

But in some rare cases the manufacturer has decided to describe multiple
i2c-devices in a single ACPI fwnode with multiple I2cSerialBus resources.

An earlier attempt to fix this in the i2c-core resulted in a lot of extra
code to support this corner-case.

This commit introduces a new i2c-multi-instantiate driver which fixes this
in a different way. This new driver can be built as a module which will
only loaded on affected systems.

This driver will instantiate a new i2c-client per I2cSerialBus resource,
using the driver_data from the acpi_device_id it is binding to to tell it
which chip-type (and optional irq-resource) to use when instantiating.

Note this driver depends on a platform device being instantiated for the
ACPI fwnode, see the i2c_multi_instantiate_ids list of ACPI device-ids in
drivers/acpi/scan.c: acpi_device_enumeration_by_parent().

Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

MAINTAINERS

@@ -367,6 +367,12 @@ L:	linux-acpi@vger.kernel.org
 S:	Maintained
 F:	drivers/acpi/arm64
 
+ACPI I2C MULTI INSTANTIATE DRIVER
+M:	Hans de Goede <hdegoede@redhat.com>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/i2c-multi-instantiate.c
+
 ACPI PMIC DRIVERS
 M:	"Rafael J. Wysocki" <rjw@rjwysocki.net>
 M:	Len Brown <lenb@kernel.org>

drivers/platform/x86/Kconfig

@@ -1218,6 +1218,17 @@ config INTEL_CHTDC_TI_PWRBTN
 	  To compile this driver as a module, choose M here: the module
 	  will be called intel_chtdc_ti_pwrbtn.
 
+config I2C_MULTI_INSTANTIATE
+	tristate "I2C multi instantiate pseudo device driver"
+	depends on I2C && ACPI
+	help
+	  Some ACPI-based systems list multiple i2c-devices in a single ACPI
+	  firmware-node. This driver will instantiate separate i2c-clients
+	  for each device in the firmware-node.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called i2c-multi-instantiate.
+
 endif # X86_PLATFORM_DEVICES
 
 config PMC_ATOM

drivers/platform/x86/Makefile

@@ -91,3 +91,4 @@ obj-$(CONFIG_PMC_ATOM)		+= pmc_atom.o
 obj-$(CONFIG_MLX_PLATFORM)	+= mlx-platform.o
 obj-$(CONFIG_INTEL_TURBO_MAX_3) += intel_turbo_max_3.o
 obj-$(CONFIG_INTEL_CHTDC_TI_PWRBTN)	+= intel_chtdc_ti_pwrbtn.o
+obj-$(CONFIG_I2C_MULTI_INSTANTIATE)	+= i2c-multi-instantiate.o

drivers/platform/x86/i2c-multi-instantiate.c

@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * I2C multi-instantiate driver, pseudo driver to instantiate multiple
+ * i2c-clients from a single fwnode.
+ *
+ * Copyright 2018 Hans de Goede <hdegoede@redhat.com>
+ */
+
+#include <linux/acpi.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+struct i2c_inst_data {
+	const char *type;
+	int gpio_irq_idx;
+};
+
+struct i2c_multi_inst_data {
+	int num_clients;
+	struct i2c_client *clients[0];
+};
+
+static int i2c_multi_inst_probe(struct platform_device *pdev)
+{
+	struct i2c_multi_inst_data *multi;
+	const struct acpi_device_id *match;
+	const struct i2c_inst_data *inst_data;
+	struct i2c_board_info board_info = {};
+	struct device *dev = &pdev->dev;
+	struct acpi_device *adev;
+	char name[32];
+	int i, ret;
+
+	match = acpi_match_device(dev->driver->acpi_match_table, dev);
+	if (!match) {
+		dev_err(dev, "Error ACPI match data is missing\n");
+		return -ENODEV;
+	}
+	inst_data = (const struct i2c_inst_data *)match->driver_data;
+
+	adev = ACPI_COMPANION(dev);
+
+	/* Count number of clients to instantiate */
+	for (i = 0; inst_data[i].type; i++) {}
+
+	multi = devm_kmalloc(dev,
+			offsetof(struct i2c_multi_inst_data, clients[i]),
+			GFP_KERNEL);
+	if (!multi)
+		return -ENOMEM;
+
+	multi->num_clients = i;
+
+	for (i = 0; i < multi->num_clients; i++) {
+		memset(&board_info, 0, sizeof(board_info));
+		strlcpy(board_info.type, inst_data[i].type, I2C_NAME_SIZE);
+		snprintf(name, sizeof(name), "%s-%s", match->id,
+			 inst_data[i].type);
+		board_info.dev_name = name;
+		board_info.irq = 0;
+		if (inst_data[i].gpio_irq_idx != -1) {
+			ret = acpi_dev_gpio_irq_get(adev,
+						    inst_data[i].gpio_irq_idx);
+			if (ret < 0) {
+				dev_err(dev, "Error requesting irq at index %d: %d\n",
+					inst_data[i].gpio_irq_idx, ret);
+				goto error;
+			}
+			board_info.irq = ret;
+		}
+		multi->clients[i] = i2c_acpi_new_device(dev, i, &board_info);
+		if (!multi->clients[i]) {
+			dev_err(dev, "Error creating i2c-client, idx %d\n", i);
+			ret = -ENODEV;
+			goto error;
+		}
+	}
+
+	platform_set_drvdata(pdev, multi);
+	return 0;
+
+error:
+	while (--i >= 0)
+		i2c_unregister_device(multi->clients[i]);
+
+	return ret;
+}
+
+static int i2c_multi_inst_remove(struct platform_device *pdev)
+{
+	struct i2c_multi_inst_data *multi = platform_get_drvdata(pdev);
+	int i;
+
+	for (i = 0; i < multi->num_clients; i++)
+		i2c_unregister_device(multi->clients[i]);
+
+	return 0;
+}
+
+static const struct i2c_inst_data bsg1160_data[]  = {
+	{ "bmc150_accel", 0 },
+	{ "bmc150_magn", -1 },
+	{ "bmg160", -1 },
+	{}
+};
+
+/*
+ * Note new device-ids must also be added to i2c_multi_instantiate_ids in
+ * drivers/acpi/scan.c: acpi_device_enumeration_by_parent().
+ */
+static const struct acpi_device_id i2c_multi_inst_acpi_ids[] = {
+	{ "BSG1160", (unsigned long)bsg1160_data },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, i2c_multi_inst_acpi_ids);
+
+static struct platform_driver i2c_multi_inst_driver = {
+	.driver	= {
+		.name = "I2C multi instantiate pseudo device driver",
+		.acpi_match_table = ACPI_PTR(i2c_multi_inst_acpi_ids),
+	},
+	.probe = i2c_multi_inst_probe,
+	.remove = i2c_multi_inst_remove,
+};
+module_platform_driver(i2c_multi_inst_driver);
+
+MODULE_DESCRIPTION("I2C multi instantiate pseudo device driver");
+MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
+MODULE_LICENSE("GPL");