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

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Date:	Tue, 13 Jan 2015 11:27:05 -0600
From:	atull <atull@...nsource.altera.com>
To:	Pavel Machek <pavel@...x.de>
CC:	Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
	Michal Simek <michal.simek@...inx.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, 13 Jan 2015, Pavel Machek wrote:

> 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...)
> 

Hi Pavel,

I still don't get what you are saying.  It's not a symlink.  I'm not
changing it.  

Alan


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