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

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Message-ID: <20150113072857.GA11760@amd>
Date:	Tue, 13 Jan 2015 08:28:57 +0100
From:	Pavel Machek <pavel@...x.de>
To:	Michal Simek <michal.simek@...inx.com>
Cc:	atull <atull@...nsource.altera.com>,
	Pantelis Antoniou <pantelis.antoniou@...sulko.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

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).

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.

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