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

From: Jarkko Sakkinen
Date: Mon Nov 20 2017 - 18:49:57 EST

On Mon, Nov 20, 2017 at 04:17:28PM -0700, Jason Gunthorpe wrote:
> 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

Oops. I was too quick. This will cause all the TPM 1.x attributes
added also for TPM 2.0. That's not a great idea. The tpm_dev_group
should be only assigned for TPM 1.x devices. This commit should only
enable addition of sysfs attributes for TPM 2.0 devices.