Re: spidev: Instantiating from DT as "spidev"

[Kyle Roeschley <kyle.roeschley@xxxxxx>]

On Thu, Nov 30, 2017 at 09:03:12AM +0100, Geert Uytterhoeven wrote:
> Hi Trent,
> 
> On Thu, Nov 30, 2017 at 3:07 AM, Trent Piepho <tpiepho@xxxxxxxxxx> wrote:
> > On Wed, 2017-11-29 at 23:18 +0100, Geert Uytterhoeven wrote:
> >> To me, the above sounds a bit contradictive: either you have
> >>   1. a simple (trivial) description, which can be handled by spidev and
> >>      userspace, and thus by just writing "<unit-addr> spidev" to a new_device
> >>      sysfs node, or

So you're suggesting that new_device can only be used to create a device which
uses spidev (without yelling about it)? That makes sense to me.

> >>   2. a complex description, for which you need a specialized in-kernel driver,
> >>      so you're gonna need a real DT node (and overlays?) to describe it.
> >>
> >> I don't think writing a complex description to a new_device sysfs node makes
> >> sense.
> >
> > Is there anything one can do with new_device that can't be done with a
> > dt fragment?
> 
> Nope.

Aren't DT overlays via configfs not yet in mainline? So if I did want to use
that mechanism, I'd have call the in-kernel API from within the SPI core.

> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

-- 
Kyle Roeschley
Software Engineer
National Instruments
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