Re: [PATCH] fpga: add simple userspace interface to trigger FPGA programming

[yves.vandervennet@linux.intel.com]

On Sun, 10 Dec 2017, Thomas Petazzoni wrote:

> Hello,
>
> On Sat, 9 Dec 2017 22:03:06 -0600, Alan Tull wrote:
>
>>> We can actually use the Linux device driver model to do that though.
>>> Assuming all peripherals behind the FPGA do have the FPGA manager's
>>> struct device as a parent (which they should), when there is a bistream
>>> load request, we ought to be able to teardown all of these child struct
>>> device's and their corresponding drivers (unbind), load the bistream,
>>> and then rebind the drivers accordingly.
>>
>> Hi Florain,
>>
>> FPGA regions are a way of handling all that plus the bridges [1] or
>> are you proposing something else?  An FPGA region knows what manager
>> to use and what bridges (if any) needs to be disabled while
>> programming is happening.  Applying a DT overlay targeting a FPGA
>> region is used to program the FPGA.
>

Thomas,

> I thought my initial patch made it clear: DT overlays are not an
> applicable solution for my use case, for two reasons:
>
> 1. My platform doesn't use Device Tree at all.
>
>
> 2. The device implemented in the FPGA is self-discoverable because it
>    sits on a PCI bus, so there is no point in doing a static
>    description of the device in a DT overlay.
How is the enumeration triggered? Do you have any bridges to take care of?

>
> So, solutions based on DT overlays are quite irrelevant for my use
> case. Am I missing something here ?

Cheers
Yves

>
> Best regards,
>
> Thomas
> -- 
> Thomas Petazzoni, CTO, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com
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