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

Pavel Machek
2015-01-13T07:56:57Z

On Tue 2015-01-13 09:40:18, Pantelis Antoniou wrote:
> Hi Pavel,
>
> > On Jan 13, 2015, at 09:28 , Pavel Machek <pavel@denx.de> wrote:
> >
> > Hi!
> >
> >>>>>>>>>> +What: /sys/class/fpga_manager/<fpga>/firmware
> >>>>>>>>>> +Date: October 2014
> >>>>>>>>>> +KernelVersion: 3.18
> >>>>>>>>>> +Contact: Alan Tull <atull@opensource.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
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