Re: [PATCH v10 0/6] Introduced new Cadence USBSS DRD Driver.

From: Pavel Machek
Date: Mon Jul 22 2019 - 07:56:51 EST


Hi!

> > >> This patch introduce new Cadence USBSS DRD driver to linux kernel.
> > >>
> > >> The Cadence USBSS DRD Controller is a highly configurable IP Core which
> > >> can be instantiated as Dual-Role Device (DRD), Peripheral Only and
> > >> Host Only (XHCI)configurations.
> > >
> > >I see you are using debugfs to select between DRD, peripheral-onlyh and XHCI...
> > >
> > >Is that good idea?
> >
> > Yes driver allows selecting dr_mode by debugfs. Controller also support such functionality
> > so I don't understand why would it not be a good idea.
> >
> > I personally use this for testing but it can be used to limit controller functionality without
> > recompiling kernel.
>
> debugfs is ONLY for debugging, never rely on it being enabled, or
> mounted, on a system in order to have any normal operation happen.
>
> So for testing, yes, this is fine. If this is going to be the normal
> api/interface for how to control this driver, no, that is not acceptable
> at all.

It makes a lot of sense for end-user to toggle this... for example
when he is lacking right cable for proper otg detection. As it is
third driver offering this functionality, I believe we should stop
treating it as debugging.

Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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