Re: [PATCH v2 0/3] Init device ids from ACPI of_compatible

From: Rafael J. Wysocki
Date: Wed Jul 13 2016 - 08:09:49 EST

On Wed, Jul 13, 2016 at 1:53 PM, Crestez Dan Leonard
<leonard.crestez@xxxxxxxxx> wrote:
> When using devicetree stuff like 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.