From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from box.trvn.ru (box.trvn.ru [45.141.101.25]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 533D4227BA5; Thu, 27 Feb 2025 09:01:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.141.101.25 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740646906; cv=none; b=YErW16ssbByrdRFr/q/zVM1sSNMoNRLyRKNcDlMZQ711Ia4XCsR4ymb2lE/v2CcGlu+aJJEg/Ly6KsaRT2581geqQ4+FY2fgQUkjzK+tHVUyNOsKOzZ8GtJyNHVuo+grfFHp9k0t1LqEFhSvJRDr8aook8FPyOX7dX0tSTuPbq0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740646906; c=relaxed/simple; bh=b6xawKG+7vT6ikY3PpBIE1Xreg7uT09HW0pKvc4K62M=; h=MIME-Version:Date:From:To:Cc:Subject:In-Reply-To:References: Message-ID:Content-Type; b=FNsSU9WwsB2mzZMQ9ukK9xENVup8u1QXbyNUVrvQHUO/DH6XFxPhzmLLRVnMiXECXKnyUPdzyMOPhiYZMRnXy31y/Gl/NmA5S/GEDpUYtnaAMRvrzkevv18M4Zt+xuM60jqz3niC00fhkVXZfairRXdGhbYO8F466w8H0pVMmsQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=trvn.ru; spf=pass smtp.mailfrom=trvn.ru; dkim=pass (2048-bit key) header.d=trvn.ru header.i=@trvn.ru header.b=CfEArneS; arc=none smtp.client-ip=45.141.101.25 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=trvn.ru Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=trvn.ru Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=trvn.ru header.i=@trvn.ru header.b="CfEArneS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=trvn.ru; s=mail; t=1740646901; bh=b6xawKG+7vT6ikY3PpBIE1Xreg7uT09HW0pKvc4K62M=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=CfEArneSe8WJxtyotOJ2xbN95m/f4sfT/IXfNy77f08LhPgnt1bk4Z3/p83gy37xj uWx9mufRu90sjk+lDGsbMyZNE2ePyw6Od+Ioeh4LYElFTEEDFQ6D/khEvrYpgtY9oq BMVblAHQqDEMbQRX0vQIlfC06ATfDDtjXQXvCEsXDmrQlEbtno/YipywtnGm139aAb P7Z/4NovCsddchw8QIoGwYvJ5SOqD6jgRaPX0EcywhoV5l5bYXMEBCGndIwsscHD1M m11KFN1Tv44Otrb//s7F/czqDVdwn2+vKdri1SpFBHBFWh7xFNWrNhMVvyRpWbl0Ti 1FgZiqYkCuBBA== Received: from authenticated-user (box.trvn.ru [45.141.101.25]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by box.trvn.ru (Postfix) with ESMTPSA id 70E3B90B1; Thu, 27 Feb 2025 14:01:41 +0500 (+05) Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Thu, 27 Feb 2025 14:01:41 +0500 From: Nikita Travkin To: Dmitry Baryshkov Cc: Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bryan O'Donoghue , Konrad Dybcio , linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] {vision/navigation}-mezzanine: Fix overlay root node In-Reply-To: References: <20250226-qcom-nonroot-overlays-v1-0-26c6e7605833@trvn.ru> Message-ID: <62a53d3222dfc516accd8dcd5e1adca0@trvn.ru> X-Sender: nikita@trvn.ru Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Dmitry Baryshkov писал(а) 27.02.2025 09:16: > On Wed, Feb 26, 2025 at 07:29:54PM +0500, Nikita Travkin wrote: >> While considering to propose WoA EL2 dt overlays upstream I was looking >> at existing overlays and noticed that some of them are broken: they put >> seemingly meaningful fixups into the overlay's "/" node, which places >> them into the overlay "metadata" itself, not into a fixup fragment to be >> applied to the actual dtb. This series fixes those two by changing to >> full path "&{/}" which should work as it was initially intended. >> >> See demonstration of the problem below: >> [...] >> $ dtc extra.dtbo >> /dts-v1/; >> >> / { >> foo; >> >> bar { >> baz; >> }; > > Is this behaviour documented somewhere? I'd say, it would be a surprise > to me. > According to dtc docs [1], 3.b) The Device Tree fragments must be compiled with the same option but they must also have a tag (/plugin/) that allows undefined references to nodes that are not present at compilation time to be recorded so that the runtime loader can fix them. so per my understanding "plugin" directive only changes the meaning of references (i.e. stuff with "&"), to generate fragments/fixups, which are the only way libfdt combines overlays into the base dtb. I suppose the old way of "manually" writing fragments (and thus writing to / as raw nodes) was kept because phandle/path based updates were added later to dtc and many overlays were still defining raw fragments... "/" also allows one to write "raw" nodes into the overlay, which is sometimes used by downstreams. (i.e. they put custom extensions to the overlay format [2] or add metadata into / of the dtbo like "compatible" values to reject incompatible overlays from applying. [3]) This is actually why I started looking here in the first place as for woa el2 overlays I was asked to add compatible metadata as, apparently, NixOS tooling requires it to validate the overlays [4]. [1] https://web.git.kernel.org/pub/scm/utils/dtc/dtc.git/tree/Documentation/dt-object-internal.txt#n120 [2] https://github.com/raspberrypi/linux/blob/rpi-6.6.y/arch/arm/boot/dts/overlays/adafruit-st7735r-overlay.dts#L73 [3] https://github.com/radxa-pkg/radxa-overlays/blob/main/arch/arm64/boot/dts/rockchip/overlays/rk3588-i2c0-m1.dts#L5 [4] https://github.com/TravMurav/slbounce/blob/main/dtbo/x1e-el2.dtso#L12 >> >> fragment@0 { >> target-path = "/"; >> >> __overlay__ { >> whatever-comes-next-after-baz; >> }; >> }; >> }; >> >> $ dtc combine.dtb >> /dts-v1/; >> >> / { >> whatever-comes-next-after-baz; >> compatible = "fake,board"; >> fake,value = <0x2a>; >> }; >> >> In the resulting dtb foo bar and baz are missing. >> >> Signed-off-by: Nikita Travkin >> --- >> Nikita Travkin (2): >> arm64: dts: qcom: qrb5165-rb5-vision-mezzanine: Fix broken overlay root >> arm64: dts: qcom: sdm845-db845c-navigation-mezzanine: Fix the overlay root >> >> arch/arm64/boot/dts/qcom/qrb5165-rb5-vision-mezzanine.dtso | 2 +- >> arch/arm64/boot/dts/qcom/sdm845-db845c-navigation-mezzanine.dtso | 2 +- >> 2 files changed, 2 insertions(+), 2 deletions(-) >> --- >> base-commit: 8433c776e1eb1371f5cd40b5fd3a61f9c7b7f3ad >> change-id: 20250226-qcom-nonroot-overlays-bfe21d33be8c >> >> Best regards, >> -- >> Nikita Travkin >>