linux-kernel - Re: [PATCH v3 4/4] i2c: Add multi-instantiate pseudo driver

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Date:   Tue, 7 Aug 2018 13:46:18 +0100
From:   John Garry <john.garry@...wei.com>
To:     Hans de Goede <hdegoede@...hat.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>,
        Wolfram Sang <wsa@...-dreams.de>
CC:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        <linux-acpi@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH v3 4/4] i2c: Add multi-instantiate pseudo driver

On 07/08/2018 09:05, 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 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().
>
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
> ---
>  MAINTAINERS                                  |   6 +
>  drivers/platform/x86/Kconfig                 |  11 ++
>  drivers/platform/x86/Makefile                |   1 +
>  drivers/platform/x86/i2c-multi-instantiate.c | 131 +++++++++++++++++++
>  4 files changed, 149 insertions(+)
>  create mode 100644 drivers/platform/x86/i2c-multi-instantiate.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 9b377508f24f..09e16d76cab7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6657,6 +6657,12 @@ F:	drivers/i2c/i2c-mux.c
>  F:	drivers/i2c/muxes/
>  F:	include/linux/i2c-mux.h
>
> +I2C MULTI INSTANTIATE DRIVER
> +M:	Hans de Goede <hdegoede@...hat.com>
> +L:	linux-i2c@...r.kernel.org
> +S:	Maintained
> +F:	drivers/drivers/platform/x86/i2c-multi-instantiate.c

This path looks incorrect

> +
>  I2C MV64XXX MARVELL AND ALLWINNER DRIVER
>  M:	Gregory CLEMENT <gregory.clement@...tlin.com>
>  L:	linux-i2c@...r.kernel.org
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 85a93453237c..8256629f58f7 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -1219,6 +1219,17 @@ 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 bases systems list multiple i2c-devices in a single ACPI

I guess that this should be "Some ACPI-based systems"

> +	  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.
> +

Thanks,
John