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

[Moritz Fischer]

On Wed, Oct 28, 2015 at 7:53 AM, atull <atull@xxxxxxxxxxxxxxxxxxxxx> 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
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