[2/2] i2c: Add 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 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@redhat.com>
---
 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

On Fri, 2018-06-08 at 23:11 +0200, Hans de Goede wrote:
> 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.
> 

You forgot to Cc Heikki.

> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  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@redhat.com>
> + */
> +
> +#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@redhat.com>");
> +MODULE_LICENSE("GPL");