Re: [PATCH RESEND v4 0/1] add sysfs exports for TPM 2 PCR registers

On Mon, Sep 07, 2020 at 02:52:08PM -0700, James Bottomley wrote:

On Mon, 2020-09-07 at 16:23 +0300, Jarkko Sakkinen wrote:

quoted

On Mon, Sep 07, 2020 at 07:38:24AM +0200, Greg KH wrote:

quoted

Please just use a binary blob format.  Binary sysfs files are
exactly what this is for, you are just passing the data through the
kernel from the hardware to userspace.

You can have 24 binary files if that makes it easier, but the
existing format really is an abuse of sysfs.

There is no existing format for TPM 2.0 ... that's part of the problem
since we certainly didn't want to carry over the TPM 1.2 format.

Ok, then no, if there is not already a binary format then you should not
use a binary sysfs file as you are then just sending a kernel structure
to userspace, not a hardware structure.

I've got to say I think binary attributes are actively evil.  I can see
they're a necessity when there's no good way to represent the data they
contain, like the bios measurement log or firmware code or a raw
interface like we do for the SMP frame code in libsas.  But when
there's a well understood and easy to produce user friendly non-binary
representation, I think dumping binary is inimical to being a good API.

Agreed.

thanks,

greg k-h