Re: [PATCH 1/2] of: Add for_each_compatible_node_from iterator

[Yegor Yefremov <yegorslists@googlemail.com>]

On Tue, Jan 5, 2016 at 9:20 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> On Tue, Jan 05, 2016 at 09:05:35AM +0100, Yegor Yefremov wrote:
>> On Tue, Jan 5, 2016 at 8:58 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
>> > On Mon, Jan 04, 2016 at 07:07:27PM +0000, Trent Piepho wrote:
>> >> On Mon, 2016-01-04 at 09:32 +0100, Sascha Hauer wrote:
>> >> > On Sat, Dec 19, 2015 at 12:13:59AM +0000, Trent Piepho wrote:
>> >> > > The existing iterator for_each_compatible_node() searches for each
>> >> > > compatible node starting from the root of the loaded device tree.
>> >> > > This means it only works on the barebox device tree and not the tree
>> >> > > to be passed to the Linux kernel, which is what an of_fixup would
>> >> > > probably want to use.
>> >> > >
>> >> > > This adds for_each_compatible_node_from(), which takes an additional
>> >> > > parameter of a root to search from.  This could be the device tree to
>> >> > > be used for the kernel.  It could also be used to search just a
>> >> > > subtree.
>> >> > >
>> >> > > Signed-off-by: Trent Piepho <tpiepho@kymetacorp.com>
>> >> >
>> >> > Applied, thanks
>> >> >
>> >> > > ---
>> >> > >
>> >> > > It's possible the fixups in cm_cogent_fixup() and hb_fixup() should
>> >> > > be using this.  It's not clear to me if they want to modify the barebox
>> >> > > device tree or the Linux device tree or both.
>> >> >
>> >> > It's always the Linux device tree that is fixed up in the OF fixups.
>> >>
>> >> Sent patch to fix them.
>> >>
>> >> Couldn't one also use the of fixup system to modify the barebox DT?  In
>> >> order to support multiple board variants, I added DT nodes that specify
>> >> what nodes should be enabled and/or disabled for different board
>> >> versions.  An OF fixup applies this to the Linux DT.  I haven't had to
>> >> modify the barebox DT for different boards but anticipate that happening
>> >> for the next board and I was planning to use the same system.
>> >
>> > I think you don't need the fixup system to accomplish that. Just hook up
>> > to an initcall early enough and modify the barebox device tree. It
>> > shouldn't be necessary to register a callback first and then wait for
>> > its execution.
>>
>> What initcall can be used to change the device tree, that is already
>> loaded into memory and before Linux is started?
>
> You want to change the device tree that is passed to Linux, right? In
> this case you can use of_register_fixup(). We were talking about
> changing the device tree that barebox uses for itself. For this
> everything after core_initcall will work. It should be early enough
> though so that the device that is ought to be changed has not probed, so
> I suggest doing it as early as possible, that would be
> postcore_initcall.

OK. Thanks.

Yegor

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