[PATCH 2/2] i2c: Add multi-instantiate pseudo driver

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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 commitintroduces 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 means that we will be instantiating 2 i2c_client-s for the first
I2cSerialBus resource, this is not pretty, but since the multi-instantiate
driver does exactly 0 i2c-transfers this is not a problem.

Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
 drivers/i2c/Kconfig                 |   8 ++
 drivers/i2c/Makefile                |   1 +
 drivers/i2c/i2c-multi-instantiate.c | 125 ++++++++++++++++++++++++++++
 3 files changed, 134 insertions(+)
 create mode 100644 drivers/i2c/i2c-multi-instantiate.c

diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index efc3354d60ae..12ca950e7549 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -120,6 +120,14 @@ config I2C_SLAVE_EEPROM
 
 endif
 
+config I2C_MULTI_INSTANTIATE
+	tristate "I2C multi instantiate pseudo device driver"
+	depends on ACPI
+	help
+	  Some ACPI bases 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.
+
 config I2C_DEBUG_CORE
 	bool "I2C Core debugging messages"
 	help
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index 72c94c60fdd1..d9c5bae1d64f 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_I2C_MUX)		+= i2c-mux.o
 obj-y				+= algos/ busses/ muxes/
 obj-$(CONFIG_I2C_STUB)		+= i2c-stub.o
 obj-$(CONFIG_I2C_SLAVE_EEPROM)	+= i2c-slave-eeprom.o
+obj-$(CONFIG_I2C_MULTI_INSTANTIATE) += i2c-multi-instantiate.o
 
 ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG
 CFLAGS_i2c-core-base.o := -Wno-deprecated-declarations
diff --git a/drivers/i2c/i2c-multi-instantiate.c b/drivers/i2c/i2c-multi-instantiate.c
new file mode 100644
index 000000000000..480b7a694eae
--- /dev/null
+++ b/drivers/i2c/i2c-multi-instantiate.c
@@ -0,0 +1,125 @@
+// 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@xxxxxxxxxx>
+ */
+
+#include <linux/acpi.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+struct i2c_inst_data {
+	const char *type;
+	int irq_idx;
+};
+
+struct i2c_multi_inst_data {
+	int no_clients;
+	struct i2c_client *clients[0];
+};
+
+static int i2c_multi_inst_probe(struct i2c_client *client)
+{
+	struct i2c_multi_inst_data *multi;
+	const struct i2c_inst_data *inst_data;
+	struct i2c_board_info board_info = {};
+	struct device *dev = &client->dev;
+	struct acpi_device *adev;
+	char name[32];
+	int i, ret;
+
+	inst_data = acpi_device_get_match_data(dev);
+	if (!inst_data) {
+		dev_err(dev, "Error ACPI match data is missing\n");
+		return -ENODEV;
+	}
+
+	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->no_clients = i;
+
+	for (i = 0; i < multi->no_clients; i++) {
+		memset(&board_info, 0, sizeof(board_info));
+		strlcpy(board_info.type, inst_data[i].type, I2C_NAME_SIZE);
+		board_info.flags = (i == 0) ? I2C_CLIENT_IGNORE_BUSY : 0;
+		snprintf(name, sizeof(name), "%s-%s", client->name,
+			 inst_data[i].type);
+		board_info.dev_name = name;
+		board_info.irq = 0;
+		if (inst_data[i].irq_idx != -1) {
+			ret = acpi_dev_gpio_irq_get(adev, inst_data[i].irq_idx);
+			if (ret < 0) {
+				dev_err(dev, "Error requesting irq at index %d: %d\n",
+					inst_data[i].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;
+		}
+	}
+
+	return 0;
+
+error:
+	while (--i >= 0)
+		i2c_unregister_device(multi->clients[i]);
+
+	return ret;
+}
+
+static int i2c_multi_inst_remove(struct i2c_client *i2c)
+{
+	struct i2c_multi_inst_data *multi = i2c_get_clientdata(i2c);
+	int i;
+
+	for (i = 0; i < multi->no_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 },
+	{}
+};
+
+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 i2c_driver i2c_multi_inst_driver = {
+	.driver	= {
+		.name = "I2C multi instantiate pseudo device driver",
+		.acpi_match_table = ACPI_PTR(i2c_multi_inst_acpi_ids),
+	},
+	.probe_new = i2c_multi_inst_probe,
+	.remove = i2c_multi_inst_remove,
+};
+
+module_i2c_driver(i2c_multi_inst_driver);
+
+MODULE_DESCRIPTION("I2C multi instantiate pseudo device driver");
+MODULE_AUTHOR("Hans de Goede <hdegoede@xxxxxxxxxx>");
+MODULE_LICENSE("GPL");
-- 
2.17.0

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