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

[Leon Romanovsky]

On Sun, Dec 06, 2020 at 05:58:32PM +0900, Blaž Hrastnik wrote:
> >
> > > More on that, the whole purpose of proposed interface is to debug and
> > > not intended to be used by any user space code.
> >
> > The purpose is to provide raw access to the Surface Serial Hub protocol,
> > just like we provide raw access to USB devices and have hidraw devices.
> >
> > So this goes a litle beyond just debugging; and eventually the choice
> > may be made to implement some functionality with userspace drivers,
> > just like we do for some HID and USB devices.
> >
> > Still I agree with you that adding new userspace API is something which
> > needs to be considered carefully. So I will look at this closely when
> > reviewing this set.
>
> To add to that: this was previously a debugfs interface but was moved to misc after review on the initial RFC:
> https://lkml.org/lkml/2020/9/24/96

There is a huge difference between the suggestion and final implementation.

Greg suggested to add new debug module to the drivers/misc that will
open char device explicitly after user loaded that module to debug this
hub. However, the author added full blown char device as a first citizen
that has all not-break-user constrains.

Thanks