linux-kernel - Re: [PATCH v8 2/4] fpga manager: add sysfs interface document

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Message-ID: <20150113075651.GB11760@amd>
Date:	Tue, 13 Jan 2015 08:56:51 +0100
From:	Pavel Machek <pavel@...x.de>
To:	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Cc:	Michal Simek <michal.simek@...inx.com>,
	atull <atull@...nsource.altera.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	jgunthorpe@...idianresearch.com, hpa@...or.com,
	Michal Simek <monstr@...str.eu>, rdunlap@...radead.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	devicetree@...r.kernel.org, robh+dt@...nel.org,
	Grant Likely <grant.likely@...aro.org>, iws@...o.caltech.edu,
	linux-doc@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	philip@...ister.org, rubini@...dd.com,
	Steffen Trumtrar <s.trumtrar@...gutronix.de>,
	jason@...edaemon.net, kyle.teske@...com, nico@...aro.org,
	Felipe Balbi <balbi@...com>, m.chehab@...sung.com,
	davidb@...eaurora.org, Rob Landley <rob@...dley.net>,
	davem@...emloft.net, cesarb@...arb.net, sameo@...ux.intel.com,
	akpm@...ux-foundation.org,
	Linus Walleij <linus.walleij@...aro.org>, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, devel@...verdev.osuosl.org,
	Alan Tull <delicious.quinoa@...il.com>,
	dinguyen@...nsource.altera.com, yvanderv@...nsource.altera.com
Subject: Re: [PATCH v8 2/4] fpga manager: add sysfs interface document

On Tue 2015-01-13 09:40:18, Pantelis Antoniou wrote:
> Hi Pavel,
> 
> > On Jan 13, 2015, at 09:28 , Pavel Machek <pavel@...x.de> wrote:
> > 
> > Hi!
> > 
> >>>>>>>>>> +What:		/sys/class/fpga_manager/<fpga>/firmware
> >>>>>>>>>> +Date:		October 2014
> >>>>>>>>>> +KernelVersion:	3.18
> >>>>>>>>>> +Contact:	Alan Tull <atull@...nsource.altera.com>
> >>>>>>>>>> +Description:	Name of the FPGA image file to load using firmware
> >>>>>>>>>> class.
> >>>>>>>>> 
> >>>>>>>>> This one is ugly: it unneccessarily passes firmware name through the
> >>>>>>>>> kernel. Just make interface and code simpler by always passing
> >>>>>>>>> "socfpga-fpga-image" or something like that.
> > ...
> > 
> >>> What is cumbersome about symlink? Why is "fake" symlink in sysfs better?
> >>> 
> >>>> Previous uses of the firmware layer has been to use it to load once after
> >>>> bootup; this is different since some use cases will want to switch out
> >>>> the FPGA image.  If someone wants there to be only one FPGA image on
> >>>> the FGPA forever, they will probably not be using this framework; their
> >>>> FPGA will probably be loaded before Linux boots up.
> >>> 
> >>> Why? I have just one image on the fpga, and would prefer to load it
> >>> from Linux.
> >> 
> >> Pavel: These patches target staging and sysfs interface doesn't need to be stable
> >> at this time. I would prefer to add these patches to staging for 3.20
> >> and feel free to send the patch which fix this.
> > 
> > Interesting way to address patch review. "We'll merge it, and you can
> > fix it up later".
> > 
> >> With your code will be exactly clear how you want to use it and we can
> >> talk about it.
> > 
> > I'm pretty sure Alan knows what I want at this point, he just does not
> > want to do it.
> > 
> > For the record, I want to drop "firmware" file, use fixed firmware
> > name, and deal with multiple firmwares in userspace (using symlink or
> > udev magic).
> 
> That’s completely bogus. Using a fixed firmware file does not respond to
> real world usage, and there are no words to describe the hacks using
> symlinks and udev in an embedded product.

> > I believe this is simplest solution, should be adequate, and is
> > certainly less ugly than implementing fake symlink in
> > /sys/.../firmware. And I have yet to hear what is wrong with that
> > suggestion.
> 
> Everything.

Can you be more specific? Current solution already has a fake symlink,
implemented badly.

Just remove it, and use real symlink (and then you can optionally
think of something better...)


									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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