Re: [PATCH] tpm: don't destroy chip device prematurely

From: Jason Gunthorpe
Date: Wed Oct 05 2016 - 12:37:40 EST

On Wed, Oct 05, 2016 at 06:15:26PM +0300, Jarkko Sakkinen wrote:

> The important thing is to notice that runtime PM requires the device
> to be "alive" and in the device hierarchy. It's a constraint...

There are two devices.

The chip->dev and the chip->dev.parent (aka the acpi_device)

Runtime PM is *only* attached to the chip->dev.parent - it does not
interact in any significant way with the chip->dev.

device_del is on the chip->dev. The acpi_device remains intact, and
fully functional.

This is why the whole patch is so confusing to me.