linux-kernel - Re: [PATCH 1/2] tpm: add sysfs attributes for tpm2

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Date:	Fri, 15 Jul 2016 09:56:58 -0700
From:	Andrey Pronin <apronin@...omium.org>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Peter Huewe <peterhuewe@....de>,
	Marcel Selhorst <tpmdd@...horst.net>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	groeck@...omium.org, smbarber@...omium.org, dianders@...omium.org
Subject: Re: [PATCH 1/2] tpm: add sysfs attributes for tpm2

On Thu, Jul 14, 2016 at 09:34:39PM -0600, Jason Gunthorpe wrote:
> On Thu, Jul 14, 2016 at 08:32:01PM -0700, Andrey Pronin wrote:
> 
> > tpm2 shares some of the attributes with tpm1 (e.g. timeouts). Do I still
> > just add those separately for tpm2 to groups[1] and keep groups[0] empty?

Just realized that if we keep tpm_add_legacy_sysfs() intact, it doesn't
create symlinks for tpm2 case for any of the groups, including groups[0].
So, in tpm_sysfs_add_device() can just do smth like:

if (chip->flags & TPM_CHIP_FLAG_TPM2)
	chip->groups[chip->groups_cnt++] = &tpm2_dev_group;
else
	chip->groups[chip->groups_cnt++] = &tpm_dev_group;

Is that acceptable? Will submit the next version along those lines.

> 
> I think so. Since the file never exists for tpm2, nothing coded for
> tpm2 will ever look in the old location.
> 

There can be a common code working with tpm1.2 that will just continue
working with tpm2 if the common attributes are in the same place. So, some
part of code can be re-used as is, but I agree that there are not too
many common attributes. Will drop for now. Can be addressed later if
the clear need arises.