linux-kernel - Re: [PATCH v11 1/4] tpm: Remove all uses of drvdata from the TPM Core

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Date:	Wed, 20 Apr 2016 08:33:41 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	Stefan Berger <stefanb@...ux.vnet.ibm.com>,
	tpmdd-devel@...ts.sourceforge.net,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 1/4] tpm: Remove all uses of drvdata from the TPM Core

On Tue, Apr 19, 2016 at 11:06:45AM -0600, Jason Gunthorpe wrote:
> On Tue, Apr 19, 2016 at 06:36:22AM -0400, Stefan Berger wrote:
> > On 04/19/2016 06:12 AM, Jarkko Sakkinen wrote:
> > >On Mon, Apr 18, 2016 at 01:26:13PM -0400, Stefan Berger wrote:
> > >>From: Jason Gunthorpe <jgunthorpe@...idianresearch.com>
> > >>
> > >>The final thing preventing this was the way the sysfs files were
> > >>attached to the pdev. Follow the approach developed for ppi and move
> > >>the sysfs files to the chip->dev with symlinks from the pdev
> > >>for compatibility. Everything in the core now sanely uses container_of
> > >>to get the chip.
> > >Can you give me a quick recap why this patch was mandatory to make the
> > >patch set work? Which regression in the earlier versions of the patch
> > >set this fixes?
> > 
> > The below patch removes usage of dev_get_drvdata() for retrieving the chip.
> > With Christophe's series dropping the priv field I now can use the drvdata
> > to store proxy_dev rather than re-introducing the priv field in the chip
> > structure. Besides that it doesn't seem necessary to use the drvdata field
> > to get from the chip to the device if a simple container_of can do it.
> 
> More specifically, since the vtpm patches use a NULL parent, the
> approach of putting the sysfs files on the parent is no longer
> workable.
> 
> The early vtpm patches simply moved the sysfs files to the tpm_chip
> when a parent is NULL, which is inconsistent for userspace. This also
> created a problem where drvdata on the chip now had to point back to
> the chip, meaning it became unusable for its new intended purpose.
> 
> The fix is to make everything uniform and put the sysfs files in the
> correct place for all drivers (under the chip) and use symlinks for
> compat.

OK, thanks for explaining this, make perfect sense now. I'll do a more
detailed review (and testing) later on.

> Jason

/Jarkko