linux-kernel - [discuss] Improve and merge a driver proposed in 2013: sysfs interfaces to access TXT config space

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Message-ID: <4febd50da7e5007a2797e0f4c969fa5edd0bf725.camel@fb.com>
Date:   Thu, 17 Feb 2022 11:47:21 +0000
From:   Dmitrii Okunev <xaionaro@...com>
To:     "pavel@....cz" <pavel@....cz>,
        "qiaowei.ren@...el.com" <qiaowei.ren@...el.com>
CC:     "matthew.garrett@...ula.com" <matthew.garrett@...ula.com>,
        "greg@...ah.com" <greg@...ah.com>,
        "xiaoyan.zhang@...el.com" <xiaoyan.zhang@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "gang.wei@...el.com" <gang.wei@...el.com>,
        Jonathan McDowell <noodles@...com>
Subject: [discuss] Improve and merge a driver proposed in 2013: sysfs
 interfaces to access TXT config space

Hello!

As far as I see the patch wasn't merged. And I see that this is the
only unsolved thread in the discussion:

On Thu, 2013-05-16 at 18:03 +0200, Pavel Machek wrote:
> On Tue 2013-05-14 01:24:43, Qiaowei Ren wrote:
> > These interfaces are located in
> > /sys/devices/platform/intel_txt/config,
> > and including totally 37 files, providing access to Intel TXT
> > configuration registers.
> 
> This looks like very wrong interface... equivalent of /dev/mem.

As an active user of these registers I hope it will be merged, so I
would like to improve this patch (or rewrite it from scratch) to make
that happen. Otherwise one have to do hackery around `/dev/mem`, which
also creates problems with proper access control.

To be able to improve the patch, could somebody clarify why exactly
this is a "very wrong interface"?

> > +What:          /sys/devices/platform/intel_txt/config/STS_raw
> > +Date:          May 2013
> > +KernelVersion: 3.9
> > +Contact:       "Qiaowei Ren" <qiaowei.ren@...el.com>
> > +Description:   TXT.STS is the general status register. This read-
> > only register
> > +               is used by AC modules and the MLE to get the status
> > of various
> > +               Intel TXT features.
> 
> This is not enough to allow people to understand what this
> does/should
> do, nor does it allow (for example) ARM people to implement something
> compatible.
> 
> Is there specific reason why "better" interface is impossible?

I would love to reuse Intel's public documentation [1] to provide a
proper description (with bit layout of the value).

[1] https://cdrdv2.intel.com/v1/dl/getContent/315168

> [...], nor does it allow (for example) ARM people to
> implement something compatible.

Do I understand correctly that a proper documentation of the registers
solves the problem?

> Is there specific reason why "better" interface is impossible?

What are specific problems with the current interface?

Best regards,
Dmitrii Okunev.