Web lists-archives.com

Re: USB "null modem" cables and related Linux driver questions




On Fri 01 Jun 2018 at 09:08:53 (-0500), Richard Owlett wrote:
> On 06/01/2018 08:21 AM, tomas@xxxxxxxxxx wrote:
> >On Fri, Jun 01, 2018 at 08:23:42AM -0400, Stefan Monnier wrote:
> >>>The one choice you have is that one of both sides takes a step
> >>>back and plays "gadget" [...]
> >
> >>The gadget API is the programming API offered by the kernel for the OTG
> >>ports: no OTG => no gadget!
> >>
> >>>[OTG]
> >
> >>More importantly, the USB ports which support OTG are driven by
> >>different hardware.
> >
> >Ah, so the hardware has to play along...
> >
> >>Right, you need both your hardware's USB port to support OTG and you
> >>need your kernel to have a driver that supports this hardware.
> >>AFAIK the driver is usually available.
> >
> >Did I say I was handwaving?
> >
> >Thanks for the clarifications!
> >
> 
> It also suggests that I frequently grasp some of the implications of
> what I read. Thank you.
> As an illustration of my mindset:
> If they had really intended USB to be *UNIVERSAL* serial bus, then
> it should have been OTG from the get go.
> P.S. I know of thousands of reasons they did not.
>      Vast majority preceded by $ ;/

I think you're misunderstanding the use of the word universal.
USB was designed to be a universal way of connecting "any"
peripherals to a PC (sensu lato) which acts as a unique,
controlling host for them.

It wasn't designed to duplicate networking hardware, communicating
between multiple hosts. Nor was OTG. OTG was designed to allow, for
example, what's normally a peripheral to be disconnected from the
host, be connected to a peripheral and effectively become a host
controlling it. Eg, a camera could act as a peripheral while
uploading photos to a PC, then act as a host when connected to an
inkjet to print them.

Cheers,
David.