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Hans de Goede authored
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: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: default avatarWolfram Sang <wsa@the-dreams.de>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
e64e8498
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Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.