real driver

[Geert Stappers <stappers@stappers.nl>]

In-Reply-To: <YOXB7FRqldZik2Xn@kroah.com>
Previous-Subject: Re: [PATCH 00/17] Rust support

On Wed, Jul 07, 2021 at 05:02:04PM +0200, Greg Kroah-Hartman wrote:
> On Wed, Jul 07, 2021 at 03:07:50PM +0100, Wedson Almeida Filho wrote:
> > > Last I looked at this thing, it was not
> > > feature-complete compared to the in-kernel binder code, has that been
> > > resolved and the needed filesystem changes added?
> > 
> > It is not feature-complete in comparison to the C one just yet, it is missing a
> > few things but not for any fundamental reason -- we were mostly focusing on the
> > kernel crate and tests.
> 
> I love it how you call "binderfs is missing" a "few things" :)
> 
> > Miguel's point is that it does implement the vast majority of binder features
> > and is non-trivial, so it could be used as evidence that useful kernel drivers
> > can be built with Rust; not just "transpiled" from C, but written with the Rust
> > safety guarantees.
> 
> As Christoph said, and I and others have said before, binder is in no
> way shape or form anything that resembles any sort of "driver" at all.
> It is a crazy IPC mechanism that is tacked onto the side of the kernel.
> Not to say that it doesn't have its usages, but the interactions between
> binder and the rest of the kernel are very small and specific.
> Something that almost no one else will ever write again.
> 
> Please work on a real driver to help prove, or disprove, that this all
> is going to be able to work properly.  There are huge unanswered
> questions that need to be resolved that you will run into when you do
> such a thing.

Suggesting virtual null modem drivers.

At userland side are character devices visible.
These /dev/tntX  come in pairs  /dev/tnt0 + /dev/tnt1,
/dev/tnt2 + /dev/tnt3, /dev/tnt4 + /dev/tnt5, etcetera.
They behave like serial ports.
The driver inbetween a /dev/tntX-pair mimicks  UARTs.

Yeah, still no true hardware driver.

Things this driver will bring:
* Providing  character devices
* Interrupts upon recieving / transmitting characters.
* Having transmit / recieve buffers
* Timer knowlege  for emulating baud rate  ( speed in bits per second )


Earlier implementations exist on the Internet. I have salvaged two:
* https://gitlab.com/stappersg/tty0tty
* https://gitlab.com/stappersg/nullmodem

 
May this idea bring this project further.


Regards
Geert Stappers

P.S.
I want the share with you the fun  /  the pun I see in "Subject: real driver"

       driver:  that what pushes forward


:-)
-- 
Silence is hard to parse