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From: Trent Piepho <>
To: Ahmad Fatoum <>
Cc: Barebox List <>
Subject: Re: [PATCH 16/17] Documentation: Add documentation for device tree overlays
Date: Wed, 23 Jun 2021 12:37:23 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Jun 22, 2021 at 11:14 PM Ahmad Fatoum <> 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.

> > +``global.of_overlay_filepattern``
> > +  This is a space separated list of file patterns. An overlay is only applied
> > +  when its filename matches one of the patterns. The patterns can contain
> > +  ``*`` and ``?`` as wildcards. When empty, all files are applied.
> Similarly, we could have ``*`` as a default.

If the default value is "*", and it's necessary to use a space
separated list, then a script adding another pattern will use
something like:
global.of_overlay_filepattern="${global.of_overlay_filepattern} new-overlay.dtb"

But that doesn't work if the variable doesn't start as empty.  Using
"global.of.filepatterns.*" as a set of variables would help.

barebox mailing list

  reply	other threads:[~2021-06-23 19:39 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 [this message]
2021-06-24  8:48       ` Sascha Hauer
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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