Re: [PATCH v12 2/6] fpga: add bindings document for simple fpga bus

[atull <atull@opensource.altera.com>]

On Wed, 28 Oct 2015, Moritz Fischer wrote:

> On Wed, Oct 28, 2015 at 7:53 AM, atull <atull@opensource.altera.com> wrote:
> 
> >> > +A Simple FPGA Bus is a bus that handles configuring an FPGA and its bridges
> >> > +before populating the devices below its node.  All this happens when a device
> >> > +tree overlay is added to the live tree.  This document describes that device
> >> > +tree overlay.
> >> > +
> >>
> >> This is not really true, is it?
> >> The driver should work without applying the overlay, e.g. the bootloader
> >> might have already done it.
> >>
> >
> > Yes it's true.  I'm not clear what you are saying.  If the bootloader has
> > programmed the FPGA, the overlay can leave out the optional properties
> > and the FPGA won't get reprogrammed; the child devices will still get
> > added and probed.  So this handles both the case where you want to reprogram
> > the FPGA under Linux and where the FPGA was programmed by a bootloader.
> 
> I think what he means is that the document explicitly calls out the overlay,
> when in theory it also works without an overlay. While being the most 'natural'
> use-case, it is not the only one ;-)
> 
> Moritz
> 

Yes, I can just take out the two sentences that refer to overlays and just 
leave:

A Simple FPGA Bus is a bus that handles configuring an FPGA and its bridges
before populating the devices below its node.

Alan