linux-kernel - Re: [RFC 7/8] fpga-region: add sysfs interface

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Message-ID: <CAAtXAHdG9GP_0LffHMyJ9T=cVuZMJrR8JNTwXXVuYQGj1y=3KQ@mail.gmail.com>
Date:   Wed, 15 Feb 2017 16:16:46 -0800
From:   Moritz Fischer <moritz.fischer@...us.com>
To:     Alan Tull <delicious.quinoa@...il.com>
Cc:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        matthew.gerlach@...ux.intel.com,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-fpga@...r.kernel.org
Subject: Re: [RFC 7/8] fpga-region: add sysfs interface

On Wed, Feb 15, 2017 at 2:42 PM, Alan Tull <delicious.quinoa@...il.com> wrote:
> On Wed, Feb 15, 2017 at 3:36 PM, Moritz Fischer
> <moritz.fischer@...us.com> wrote:
>> Jason,
>>
>> On Wed, Feb 15, 2017 at 1:15 PM, Jason Gunthorpe
>> <jgunthorpe@...idianresearch.com> wrote:
>>> On Wed, Feb 15, 2017 at 12:54:27PM -0800, Moritz Fischer wrote:
>>>
>>>> Well I don't know ;-) With something fdt based we already have
>>>> parsers there,
>>>
>>> Not sure.. How does incbin work in DTB?
>>>
>>> We have the FPGA in a s/g list so we cannot pass the entire file to
>>> libfdt - is that consistent with incbin?
>>
>> Well you could attach the (for lack of better word) blob to the beginning,
>> instead of doing incbin
>>
>>> Can we force a specific alignment for the included data?
>>
>> I'd say probably, but haven't checked.
>>
>>> How complex will the userspace tool be to make the image?
>>
>> Userspace can be as complex as it needs to be, imho, if it makes
>> kernel space easier & safer.
>>
>> I'll need to do some more reading over the weekend before I can make
>> more sensible comments :)
>>
>> Thanks,
>>
>> Moritz
>
> Another thought I have about this is that adding the header to
> bitstreams can be a piece of independence from DT for systems that
> aren't already using DT.  This includes x86 in Linux.  It also
> includes other OS's that aren't using DT, they can reuse the same
> image files without having to add dtc.  As much as I like DT, it is
> something I'm having to think about.

Just to clarify:
I was proposing using the binary format of dts, not actually requiring
devicetree
for it to work. There's plenty of people running u-boot on x86 using FIT images
to boot.

W.r.t to Jason's script, it's there. Almost any company dealing with
Xilinx FPGAs
will have one of those. We have one, too. I recall having seen another one made
and shared by Mike @ topic.

While it's a good starting point ,I *really* don't like the idea
parsing user-land
provided strings in kernel space in a parser that we open-code.

Good discussion ;-)

Cheers,
Moritz