Re: [PATCH v4 1/1] tpm: add sysfs exports for all banks of PCR registers

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Tue, Aug 18, 2020 at 07:12:09PM +0300, Jarkko Sakkinen wrote:
> On Mon, Aug 17, 2020 at 02:35:06PM -0700, James Bottomley wrote:
> > Create sysfs per hash groups with 24 PCR files in them one group,
> > named pcr-<hash>, for each agile hash of the TPM.  The files are
> > plugged in to a PCR read function which is TPM version agnostic, so
> > this works also for TPM 1.2 but the hash is only sha1 in that case.
> > 
> > Note: the macros used to create the hashes emit spurious checkpatch
> > warnings.  Do not try to "fix" them as checkpatch recommends, otherwise
> > they'll break.
> > 
> > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > Tested-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> 
> I have hard time understanding why this is required.
> 
> You can grab the information through /dev/tpm0 just fine.

I just think it is principally wrong to add sysfs files if they don't
have any measurable value other than perhaps some convenience.

It is trival to write only a libc dependent program that outputs PCRs.

I think this is essentially an user space problem that is getting sorted
out with kernel code.

/Jarkko