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

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Message-ID: <20161005163734.GD18636@obsidianresearch.com>
Date:   Wed, 5 Oct 2016 10:37:34 -0600
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     "Winkler, Tomas" <tomas.winkler@...el.com>,
        "tpmdd-devel@...ts.sourceforge.net" 
        <tpmdd-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: don't destroy chip device prematurely

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.

Jason