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docs:guide-developer:defining-firmware-partitions [2018/11/27 09:40] – created bobafetthotmaildocs:guide-developer:defining-firmware-partitions [2020/04/20 16:25] (current) – you still need mtd splitting, just not the original one karlp
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 +====== Device Tree Usage in OpenWrt (DTS) ======
 +
 +Current development (2019) uses kernel based on Device Tree (DT) files (.dts, .dtsi, .dtb) rather than the older "mach" files.
 +
 +This page tries to pull together some of the knowledge about DT usage and conventions used by the OpenWrt project.
 +
 +===== References =====
 +
 +  * https://elinux.org/Device_Tree_Reference
 +  * https://elinux.org/Device_Tree_Mysteries
 +  * https://elinux.org/Device_Tree_Source_Undocumented
 +  * https://developer.toradex.com/device-tree-customization
 +  * https://events.static.linuxfound.org/sites/events/files/slides/petazzoni-device-tree-dummies.pdf
 +  * Linux binding defintions, in source or online at https://www.kernel.org/doc/Documentation/devicetree/bindings/
 +  * OpenWrt wiki on Defining software partitions in all DTS targets
 +  * https://devicetree-specification.readthedocs.io/en/latest/source-language.html
 +  * https://github.com/devicetree-org/devicetree-specification/blob/master/source/source-language.rst
 +
 +===== General =====
 +
 +Use c-style ''#include'' instead of DT-specific ''/include/''
 +
 +If possible, license the content as ''%%// SPDX-License-Identifier: GPL-2.0-or-later OR MIT%%''
 +
 +Use tab indentation -- see also https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst
 +
 +While upstream, architecture-specific .dtsi files //may// remain stable (such as ''qcom-ipq4019.dtsi''), board-specific files (such as ''qcom-ipq4019-ap.dk07.1.dtsi'') may change, causing breakage to specific devices, perhaps just one, that may go unnoticed. At least if, for example, the generic IPQ4019 .dtsi changes, there is a chance that it would be seen quickly by or more of the boards that use that SoC.
 +
 +
 ===== Defining software partitions in all DTS targets ===== ===== Defining software partitions in all DTS targets =====
 +
 +Partition nodes should be named ''partition@<start address>''
 +
 +Boot loader binaries, firmware, and configuration partitions (such as "ART") should be marked as read-only. This helps reduce the risk of users following outdated or questionable advice in using low-level writes. Users advanced enough to need to write these partitions should be sophisticated enough to be able to compile their own kernel to do so. 
 +
 +The MTD labels of "firmware" and "ubi" have special meaning to the OpenWrt kernel.
 +
 +See below on supplying the proper "compatible" label so that the OpenWrt kernel can properly "split" the partition and ''CONFIG_MTD_SPLIT_FIRMWARE'' is not needed. (note that ''CONFIG_MTD_SPLIT_UIMAGE_FW'' is still required!)
  
 <WRAP center round info 80%> <WRAP center round info 80%>
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 I'd like all DTS supported devices to use that "compatible" and disable CONFIG_MTD_SPLIT_FIRMWARE eventually. I'd like all DTS supported devices to use that "compatible" and disable CONFIG_MTD_SPLIT_FIRMWARE eventually.
 +
 +//Wiki note: This objective may be a challenge for dual-firmware units as the partition to be split will be different depending on which was selected by the boot loader.//
  
 1) Default uimage\\ 1) Default uimage\\
  • Last modified: 2018/11/27 09:40
  • by bobafetthotmail