linux-kernel - Re: [Regression] TPM char device not created if TPM 1.2 is disabled, but visible

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Message-ID: <7BE685E0-F107-4E1A-A9E1-72DCB58186AE@fb.com>
Date:   Wed, 7 Mar 2018 22:34:38 +0000
From:   Sahil Rihan <srihan@...com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Alexei Starovoitov" <ast@...com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Subject: Re: [Regression] TPM char device not created if TPM 1.2 is disabled,
 but visible

> On 3/6/18, 3:14 AM, "Jarkko Sakkinen" <jarkko.sakkinen@...ux.intel.com> wrote:
> 
>   On Mon, 2018-03-05 at 19:28 +0000, Sahil Rihan wrote:
> > Agree on keeping the warning. 
> > 
> > I'm guessing you want to return -ENODEV from tpm_bios_log_setup. Doing it from
> > tpm_read_log_acpi will just fall through to calling tpm_read_log_of, which I
> > think will end up returning -EIO again.
> > 
> > In terms of semantics I'm not sure if -ENODEV is the right return code if the
> > BIOS event log is absent. I guess you can claim it's some sort of "device". I
> > don’t have a strong opinion here.
> > 
> > Sahil
>     
> You are absolutely right. Printing warning and returning zero would be
> the right measure to take.
>     
> One more cosmetic detail. Should the log level be info or warn? I mean
> as far as I'm concerned everything is in a legit state.
>     
> /Jarkko
   
Yeah, I tend to agree. I think INFO should be fine. 

My reasoning is as follows: if the TPM is disabled, you shouldn't really be checking/using the BIOS event log measurements anyway. 

Sahil