linux-kernel - Re: [PATCH] tpm: Add explicit chip->ops locking for sysfs attributes.

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Message-ID: <20171120231728.GR29075@ziepe.ca>
Date:   Mon, 20 Nov 2017 16:17:28 -0700
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <peterhuewe@....de>,
        Andrey Pronin <apronin@...omium.org>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tpm: Add explicit chip->ops locking for sysfs attributes.

On Mon, Nov 20, 2017 at 02:45:23PM -0800, Guenter Roeck wrote:

> "tpm: Enable sysfs support for TPM2 devices
> 
> Access to chip->ops on TPM2 devices requires an explicit lock,
> since the pointer is set to NULL in tpm_class_shutdown().
> Implement that lock for sysfs access functions and enable sysfs
> support for TPM2 devices."

Wait.. one of the reasons we let it go with no sysfs for so long was
because there was not many sysfs files that were compatible with tpm2?

For TPM2 we have sort of had an API break of sorts from TPM1 in a
couple places around sysfs, and I would like to not re-introduce any
badly designed sysfs files for TPM2..

So.. When you apply this patch, what changes actually happen in the
sysfs directory?

Jason