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From: Sascha Hauer <s.hauer@pengutronix.de>
To: Trent Piepho <trent.piepho@igorinstitute.com>
Cc: Ahmad Fatoum <a.fatoum@pengutronix.de>,
	Barebox List <barebox@lists.infradead.org>
Subject: Re: [PATCH 16/17] Documentation: Add documentation for device tree overlays
Date: Thu, 24 Jun 2021 10:48:02 +0200	[thread overview]
Message-ID: <20210624084802.GW9782@pengutronix.de> (raw)
In-Reply-To: <CAMHeXxNoxju8HzqCPMrMyvCUP67WFH6QBOoWLM-cN5n7jeatKg@mail.gmail.com>

On Wed, Jun 23, 2021 at 12:37:23PM -0700, Trent Piepho wrote:
> On Tue, Jun 22, 2021 at 11:14 PM Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
> >
> > Hi,
> >
> > some bikeshedding incoming.
> 
> Well, while we're out here at the shed...
> 
> > Convention seems to be that attributes of the same thing are preceded by a `.', e.g.:
> >
> > global.of.overlay.dir
> > global.of.overlay.compatible
> > global.of.overlay.filepattern
> 
> This looks a lot more Barebox-like to me.
> 
> > (I think the `.' between of and overlay is not a bad idea, as we may decide to have e.g.
> >  global.of.compatible in future)
> 
> Are these only used when bootm is run? Aren't most magivars that work
> this way in the namespace "global.bootm"?
> 
> > > +``global.of_overlay_compatible``
> > > +  This is a space separated list of compatibles. Only overlays matching one of
> > > +  these compatibles will be applied. When this list is empty then all overlays
> > > +  will be applied. Overlays that don't have a compatible are considered being
> > > +  always compatible.
> >
> > Makes sense.
> 
> I've always thought the way Barebox's global.linux.bootargs.*
> variables worked was nice.  It avoids different things that add
> arguments for different reasons from interacting with each other
> trying to write to a single variable.
> 
> There's a similar process with overlays.  Some overlays are based on
> the board variant.  Then an add-on board might bring in an overlay.
> Then another overlay from a second add-on board that is unrelated to
> the 1st.  Then an overlay to configure something at boot time, like
> add an LED trigger at boot.  It's so much easier to just set or unset
> a single variable, than to need to worry about appending or removing
> or modifying a string inside a space separated list.

I see what you mean. I talked to Ahmad and I have now implemented a
filter mechanism for overlays which can be extended when a board has
the need to do so. I think the result is quite flexible and already
quite complex. I am not against using global.linux.bootargs.* style
multi variables for the filepatterns, but maybe we can leave that out
for now until somebody has a concrete need for this.

Sascha


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  reply	other threads:[~2021-06-24  8:49 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23  5:16 [PATCH v2 00/17] Apply device tree overlays to kernel tree Sascha Hauer
2021-06-23  5:16 ` [PATCH 01/17] fdt: Check blob size during unflattening Sascha Hauer
2021-06-23  5:16 ` [PATCH 02/17] firmware: make device_node argument non const Sascha Hauer
2021-06-23  5:16 ` [PATCH 03/17] libbb: Add find_path function Sascha Hauer
2021-06-23  5:16 ` [PATCH 04/17] firmware: consolidate ifdefs Sascha Hauer
2021-06-23  5:16 ` [PATCH 05/17] firmware: Add search path Sascha Hauer
2021-06-23  5:16 ` [PATCH 06/17] firmware: Fix device_node matching Sascha Hauer
2021-06-23  5:16 ` [PATCH 07/17] firmware: recognize by reproducible name Sascha Hauer
2021-06-23  5:16 ` [PATCH 08/17] blspec: Set firmware searchpath Sascha Hauer
2021-06-23  5:16 ` [PATCH 09/17] overlay: only apply compatible trees Sascha Hauer
2021-06-23  5:16 ` [PATCH 10/17] overlay: Add of_overlay_apply_file() Sascha Hauer
2021-06-23  5:16 ` [PATCH 11/17] firmware: Load from global search path Sascha Hauer
2021-06-23  5:16 ` [PATCH 12/17] blspec: Rework firmware load Sascha Hauer
2021-06-23  5:16 ` [PATCH 13/17] of_overlay: apply overlays during booting Sascha Hauer
2021-06-23  5:16 ` [PATCH 14/17] blspec: Apply overlays from rootfs Sascha Hauer
2021-06-23  5:16 ` [PATCH 15/17] doc: devicetree: Refer to internal device tree also as live tree Sascha Hauer
2021-06-23  5:16 ` [PATCH 16/17] Documentation: Add documentation for device tree overlays Sascha Hauer
2021-06-23  6:13   ` Ahmad Fatoum
2021-06-23 19:37     ` Trent Piepho
2021-06-24  8:48       ` Sascha Hauer [this message]
2021-06-23  5:16 ` [PATCH 17/17] of_firmware: Fix handling of firmware-name property Sascha Hauer
  -- strict thread matches above, loose matches on Subject: below --
2021-03-10 13:28 [PATCH 00/17] Apply device tree overlays to kernel tree Sascha Hauer
2021-03-10 13:28 ` [PATCH 16/17] Documentation: Add documentation for device tree overlays Sascha Hauer

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