Re: [RFC PATCH v2 2/3] of: Add support for -@ when compiling overlays

From: Rob Herring <robh@kernel.org>
To: Detlev Casanova <detlev.casanova@collabora.com>
Cc: linux-kernel@vger.kernel.org, arnd@arndb.de,
	bcm-kernel-feedback-list@broadcom.com,
	devicetree@vger.kernel.org, f.fainelli@gmail.com,
	frowand.list@gmail.com, linux-arm-kernel@lists.infradead.org,
	linux-rpi-kernel@lists.infradead.org, masahiroy@kernel.org,
	michal.lkml@markovi.net, ndesaulniers@google.com,
	nsaenz@kernel.org, olof@lixom.net, rjui@broadcom.com,
	sbranden@broadcom.com, soc@kernel.org, stefan.wahren@i2se.com
Subject: Re: [RFC PATCH v2 2/3] of: Add support for -@ when compiling overlays
Date: Wed, 27 Apr 2022 16:24:39 -0500	[thread overview]
Message-ID: <Ymm0l2/oGpt/SeDO@robh.at.kernel.org> (raw)
In-Reply-To: <20220427185243.173594-3-detlev.casanova@collabora.com>

On Wed, Apr 27, 2022 at 02:52:42PM -0400, Detlev Casanova wrote:
> This commit adds an option to compile all device trees with -@ to add the
> symbol table to the Device Tree Blobs.

Why would we want to tie this to the kernel config?

Globally enabling it has already been discussed and rejected.

> It prepares the introduction of device tree overlays that are
> not applied on device trees at compile time (dtbo files.)
> 
> These device tree overlays will be used by either a bootloader or a
> linux userspace tool to extend the base device tree.
> 
> This is used e.g. for drivers that need device tree nodes for optional
> non plug and play devices, like an external DSI touchscreen panel that
> embeds different i2c devices to control it.

You can already set DTC_FLAGS per directory (and target?), so enable it 
for the dtbs that have overlays.

> 
> Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>
> ---
>  drivers/of/Kconfig   | 8 ++++++++
>  scripts/Makefile.lib | 9 +++++++--
>  2 files changed, 15 insertions(+), 2 deletions(-)