Re: [PATCH 3/4] OMAPDSS: panel-sharp-ls037v7dw01: add device tree support

[Sebastian Reichel <sre@ring0.de>]

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On Fri, May 16, 2014 at 09:07:17AM -0700, Tony Lindgren wrote:
> * Tomi Valkeinen <tomi.valkeinen@ti.com> [140515 22:57]:
> > On 15/05/14 21:21, Tony Lindgren wrote:
> > >> But you're right, having "sharp,ls037v7dw01-omap-dss" in the .dts is an
> > >> alternative for the compatible-string conversion we do now. I guess it's
> > >> a matter of taste, but I rather hide it inside the kernel, in an
> > >> internal omapdss file, than pollute the .dts files with those compatible
> > >> strings.
> > > 
> > > Well it avoid you parsing through all the nodes during booting
> > > and leaves out the function to do remapping. And removes the need
> > > for maintaining a custom display mapping table. I'd say that's a
> > > pretty good list of advantages right there :)
> > 
> > Yep... I don't know. Maybe I'm being too careful about doing wrong
> > things with .dts. I just like it more if any hacks are in kernel code,
> > which I can remove without anyone noticing.
> > 
> > Anyway, we already have board.dts files using the non-omapified
> > compatible strings in the mainline, so if I would now add the omapified
> > compatible strings to .dts files, those old board.dts files would break.
> > 
> > So I guess the choice has already been made.
> 
> I really think you should remove this misuse of device tree code ASAP.
> It's better to fix it up now than carry the hack for next two years
> and keep on adding to it.

IMHO appending -omap-dss to a random device is an even bigger hack,
since its adding lots of bloat to the API. Let's assume there is
another OS using DT for ARM, but has no proper API for SPI
controllers and it introduces your hack to SPI devices. That would
mean each SPI device has -omap-spi appended (or -exynos-spi,
-foo-spi, ...). At least I would blame them for creating a huge
unmaintainable mess.

I think Tomi's workaround is a much better hack, since it keeps the
API clean. If the code simply prefixes "omapdss," to all
"child"-devices of omapdss it can be left mostly untouched, too.

-- Sebastian

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