linux-kernel - Re: [PATCH v2 1/3] ftpm: dt-binding: add dts documentation for fTPM driver

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Date:   Wed, 10 Apr 2019 14:57:08 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>, Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Corbet <corbet@....net>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        linux-integrity@...r.kernel.org, linux-kernel@...rosoft.com,
        thiruan@...rosoft.com, bryankel@...rosoft.com
Subject: Re: [PATCH v2 1/3] ftpm: dt-binding: add dts documentation for fTPM
 driver

On Wed, Apr 10, 2019 at 01:53:59PM -0400, Sasha Levin wrote:
> On Wed, Apr 10, 2019 at 02:03:16PM -0300, Jason Gunthorpe wrote:
> > On Wed, Apr 10, 2019 at 12:01:37PM -0500, Rob Herring wrote:
> > > On Wed, Apr 10, 2019 at 11:19 AM Sasha Levin <sashal@...nel.org> wrote:
> > > >
> > > > On Tue, Apr 09, 2019 at 04:18:29PM -0500, Rob Herring wrote:
> > > > >On Tue, Apr 9, 2019 at 1:50 PM Sasha Levin <sashal@...nel.org> wrote:
> > > > >>
> > > > >> The parameters are similar to the ones used by IBM's vTPM and the
> > > > >> various I2C tpm drivers.
> > > > >
> > > > >Bindings describe h/w (or firmware interfaces in this case), not drivers.
> > > > >
> > > > >>
> > > > >> Signed-off-by: Sasha Levin <sashal@...nel.org>
> > > > >>  .../bindings/security/tpm/tpm_ftpm_tee.txt          | 13 +++++++++++++
> > > > >>  .../devicetree/bindings/vendor-prefixes.txt         |  1 +
> > > > >>  2 files changed, 14 insertions(+)
> > > > >>  create mode 100644 Documentation/devicetree/bindings/security/tpm/tpm_ftpm_tee.txt
> > > > >>
> > > > >> diff --git a/Documentation/devicetree/bindings/security/tpm/tpm_ftpm_tee.txt b/Documentation/devicetree/bindings/security/tpm/tpm_ftpm_tee.txt
> > > > >> new file mode 100644
> > > > >> index 000000000000..20fca67a56c4
> > > > >> +++ b/Documentation/devicetree/bindings/security/tpm/tpm_ftpm_tee.txt
> > > > >> @@ -0,0 +1,13 @@
> > > > >> +Required properties:
> > > > >> +- compatible: should be "microsoft,ftpm"
> > > > >> +- linux,sml-base: 64-bit base address of the reserved memory allocated
> > > > >> +                 for the firmware event log
> > > > >> +- linux,sml-size: size of the memory allocated for the firmware event log
> > > > >
> > > > >Firmware is defining linux specific properties? What if I want to run
> > > > >BSD? We should use 'reg' here instead.
> > > >
> > > > This is based on already existing code that defines these names, see
> > > > tpm_read_log_of() in drivers/char/tpm/eventlog/of.c .
> > > 
> > > BTW, that probably needs updating to handle endianness correctly.
> > 
> > IIRC this legacy IBM code has broken endianness in the firmware..
> > 
> > All that stuff in read_log_of, and the related DT stuff, is historical
> > IBM special case-ness and should not be copied into new things.
> 
> The fTPM driver does not use it on it's own, so I guess I can just drop
> this patch then?

If your ARM system boots via EFI then it should pass the firmware
event log through EFI mechanisms, IIRC.

Otherwise maybe you could make a case for using this, but only if the
old IBM stuff is perfectly emulated, bugs and all.

Do you even have an event log?

Jason