linux-kernel - Re: [PATCH v2 0/3] Init device ids from ACPI of

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Date:	Wed, 13 Jul 2016 14:09:30 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Crestez Dan Leonard <leonard.crestez@...el.com>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Jarkko Nikula <jarkko.nikula@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Len Brown <lenb@...nel.org>,
	linux-i2c <linux-i2c@...r.kernel.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	linux-spi <linux-spi@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Octavian Purdila <octavian.purdila@...el.com>
Subject: Re: [PATCH v2 0/3] Init device ids from ACPI of_compatible

On Wed, Jul 13, 2016 at 1:53 PM, Crestez Dan Leonard
<leonard.crestez@...el.com> wrote:
> When using devicetree stuff like i2c_client.name or spi_device.modalias
> is initialized to the first DT compatible id with the vendor prefix
> stripped. Since some drivers rely on this in order to differentiate between
> hardware variants try to replicate it when using ACPI with DT ids.
>
> This also makes it so that the i2c_device_id parameter passed to probe is
> non-NULL when matching with ACPI and DT ids.
>
> These patches are on top of linux-pm/linux-next. I delayed v2 until ACPI
> overlays got in in order to avoid conflicts. I tested using ACPI overlays but
> there is no actual dependency. This series just extends the PRP0001 feature to
> be more useful for I2C/SPI.
>
> The patches only touches the ACPI-specific parts of the i2c and spi core.
>
> Here is an example .dsl for an SPI accelerometer connected to minnowboard max:
>
> Device (ACCL)
> {
>     Name (_ADR, Zero)
>     Name (_HID, "PRP0001")
>     Name (_CID, "PRP0001")

This is bad ASL.

Generally, it is a bug to use the same device ID in both _HID and
_CID.  It will work, but it is incorrect.

Thanks,
Rafael