linux-kernel - Re: [PATCH v2 0/9] Add support for Microsoft Surface System Aggregator Module

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Date:   Sun, 6 Dec 2020 10:35:24 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Maximilian Luz <luzmaximilian@...il.com>,
        linux-kernel@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Barnabás Pőcze <pobrn@...tonmail.com>,
        Arnd Bergmann <arnd@...db.de>, Rob Herring <robh@...nel.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Jonathan Corbet <corbet@....net>,
        Blaž Hrastnik <blaz@...n.io>,
        Dorian Stoll <dorian.stoll@...p.io>,
        platform-driver-x86@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 0/9] Add support for Microsoft Surface System
 Aggregator Module

On Sun, Dec 06, 2020 at 09:32:30AM +0100, Greg Kroah-Hartman wrote:
> On Sun, Dec 06, 2020 at 09:07:05AM +0200, Leon Romanovsky wrote:
> > On Thu, Dec 03, 2020 at 10:26:31PM +0100, Maximilian Luz wrote:
> > > Hello,
> > >
> > > Here is version two of the Surface System Aggregator Module (SAM/SSAM)
> > > driver series, adding initial support for the embedded controller on 5th
> > > and later generation Microsoft Surface devices. Initial support includes
> > > the ACPI interface to the controller, via which battery and thermal
> > > information is provided on some of these devices.
> > >
> > > The previous version and cover letter detailing what this series is
> > > about can be found at
> > >
> > >   https://lore.kernel.org/platform-driver-x86/20201115192143.21571-1-luzmaximilian@gmail.com/
> > >
> > > This patch-set can also be found at the following repository and
> > > reference, if you prefer to look at a kernel tree instead of these
> > > emails:
> > >
> > >   https://github.com/linux-surface/kernel tags/s/surface-aggregator/v2
> > >
> > > Thank you all for the feedback to v1, I hope I have addressed all
> > > comments.
> >
> >
> > I think that it is too far fetched to attempt and expose UAPI headers
> > for some obscure char device that we are all know won't be around in
> > a couple of years from now due to the nature of how this embedded world
> > works.
>
> No, that's not ok, we do this for loads of devices out there.  If there
> is a device that wants to be supported for Linux, and a developer that
> wants to support it, we will take it.
>
> > More on that, the whole purpose of proposed interface is to debug and
> > not intended to be used by any user space code.
>
> I thought that debugfs was going to be used for most of the debugging
> code, or has that changed in newer versions of this patchset?

https://lore.kernel.org/lkml/20201203212640.663931-9-luzmaximilian@gmail.com/#Z30include:uapi:linux:surface_aggregator:cdev.h

+ * Definitions, structs, and IOCTLs for the /dev/surface/aggregator misc
+ * device. This device provides direct user-space access to the SSAM EC.
+ * Intended for debugging and development.

>
> thanks,
>
> greg k-h