linux-kernel - Re: [PATCH v2 2/3] fpga manager: framework core

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Date:	Mon, 8 Dec 2014 22:55:19 +0000
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Grant Likely <grant.likely@...aro.org>
Cc:	Pavel Machek <pavel@...x.de>, atull@...nsource.altera.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Simek <monstr@...str.eu>,
	Michal Simek <michal.simek@...inx.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
	Rob Herring <robh+dt@...nel.org>,
	Ira Snyder <iws@...o.caltech.edu>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>, philip@...ister.org,
	rubini <rubini@...dd.com>,
	Steffen Trumtrar <s.trumtrar@...gutronix.de>,
	Jason <jason@...edaemon.net>, kyle.teske@...com,
	Nicolas Pitre <nico@...aro.org>,
	"Balbi, Felipe" <balbi@...com>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	David Brown <davidb@...eaurora.org>,
	Rob Landley <rob@...dley.net>,
	David Miller <davem@...emloft.net>, cesarb@...arb.net,
	"sameo@...ux.intel.com" <sameo@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alan Tull <delicious.quinoa@...il.com>,
	dinguyen@...nsource.altera.com,
	Yves Vandervennet <yvanderv@...nsource.altera.com>
Subject: Re: [PATCH v2 2/3] fpga manager: framework core

On Sat, 6 Dec 2014 13:00:17 +0000
Grant Likely <grant.likely@...aro.org> wrote:

> On Fri, Oct 24, 2014 at 11:52 AM, Pavel Machek <pavel@...x.de> wrote:
> > Hi!
> >
> >> * /sys/class/fpga_manager/<fpga>/firmware
> >>   Name of FPGA image file to load using firmware class.
> >>   $ echo image.rbf > /sys/class/fpga_manager/<fpga>/firmware
> >
> > I .. still don't think this is good idea. What about namespaces?
> > The path corresponds to path in which namespace?
> 
> I don't understand your concern here. This allows userspace to name
> the FPGA bitstream that the kernel will use during request_firmware(),
> and it will show up as the $FIRMWARE value in the uevent file, but it
> is still the responsibility of userspace to choose what to load, and
> it can freely ignore the setting of $FIRMWARE if it needs to.

I think the entire model here is basically pedicated on a bogus
assumption that an FPGA is a one shot device. It's not. It's a fast
reloadable reusable device. A lot of work being done with FPGAs in
operating systems already involves basically task switching and
scheduling FPGAs as a shared resource pool. Trying to nail something
together with request_firmware is several years behind the curve.

>From userspace it needs to be a open, load, use, close type model, not a
static or semi-static pile of mappings.

Alan
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