mirror of https://gitee.com/openkylin/linux.git
docs: dt: convert overlay-notes.txt to ReST format
- Add a SPDX header; - Adjust document title; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add it to devicetree/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Rob Herring <robh@kernel.org>
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Mauro Carvalho Chehab
Rob Herring
parent
218e1b3d10
commit
642e6e5ce0
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@ -12,3 +12,4 @@ Open Firmware and Device Tree
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changesets
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dynamic-resolution-notes
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of_unittest
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overlay-notes
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@ -1,5 +1,8 @@
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.. SPDX-License-Identifier: GPL-2.0
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=========================
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Device Tree Overlay Notes
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-------------------------
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=========================
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This document describes the implementation of the in-kernel
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device tree overlay functionality residing in drivers/of/overlay.c and is a
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@ -15,9 +18,9 @@ Since the kernel mainly deals with devices, any new device node that result
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in an active device should have it created while if the device node is either
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disabled or removed all together, the affected device should be deregistered.
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Lets take an example where we have a foo board with the following base tree:
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Lets take an example where we have a foo board with the following base tree::
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---- foo.dts -----------------------------------------------------------------
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---- foo.dts ---------------------------------------------------------------
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/* FOO platform */
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/dts-v1/;
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/ {
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@ -33,11 +36,12 @@ Lets take an example where we have a foo board with the following base tree:
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peripheral1 { ... };
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};
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};
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---- foo.dts -----------------------------------------------------------------
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---- foo.dts ---------------------------------------------------------------
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The overlay bar.dts,
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::
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---- bar.dts - overlay target location by label ------------------------------
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---- bar.dts - overlay target location by label ----------------------------
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/dts-v1/;
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/plugin/;
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&ocp {
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@ -47,11 +51,11 @@ The overlay bar.dts,
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... /* various properties and child nodes */
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};
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};
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---- bar.dts -----------------------------------------------------------------
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---- bar.dts ---------------------------------------------------------------
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when loaded (and resolved as described in [1]) should result in foo+bar.dts
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when loaded (and resolved as described in [1]) should result in foo+bar.dts::
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---- foo+bar.dts -------------------------------------------------------------
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---- foo+bar.dts -----------------------------------------------------------
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/* FOO platform + bar peripheral */
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/ {
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compatible = "corp,foo";
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@ -72,7 +76,7 @@ when loaded (and resolved as described in [1]) should result in foo+bar.dts
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};
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};
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};
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---- foo+bar.dts -------------------------------------------------------------
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---- foo+bar.dts -----------------------------------------------------------
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As a result of the overlay, a new device node (bar) has been created
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so a bar platform device will be registered and if a matching device driver
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@ -84,9 +88,9 @@ in the base DT. In this case, the target path can be provided. The target
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location by label syntax is preferred because the overlay can be applied to
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any base DT containing the label, no matter where the label occurs in the DT.
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The above bar.dts example modified to use target path syntax is:
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The above bar.dts example modified to use target path syntax is::
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---- bar.dts - overlay target location by explicit path ----------------------
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---- bar.dts - overlay target location by explicit path --------------------
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/dts-v1/;
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/plugin/;
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&{/ocp} {
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@ -96,7 +100,7 @@ The above bar.dts example modified to use target path syntax is:
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... /* various properties and child nodes */
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}
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};
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---- bar.dts -----------------------------------------------------------------
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---- bar.dts ---------------------------------------------------------------
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Overlay in-kernel API
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@ -104,12 +108,12 @@ Overlay in-kernel API
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The API is quite easy to use.
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1. Call of_overlay_fdt_apply() to create and apply an overlay changeset. The
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return value is an error or a cookie identifying this overlay.
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1) Call of_overlay_fdt_apply() to create and apply an overlay changeset. The
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return value is an error or a cookie identifying this overlay.
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2. Call of_overlay_remove() to remove and cleanup the overlay changeset
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previously created via the call to of_overlay_fdt_apply(). Removal of an
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overlay changeset that is stacked by another will not be permitted.
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2) Call of_overlay_remove() to remove and cleanup the overlay changeset
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previously created via the call to of_overlay_fdt_apply(). Removal of an
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overlay changeset that is stacked by another will not be permitted.
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Finally, if you need to remove all overlays in one-go, just call
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of_overlay_remove_all() which will remove every single one in the correct
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@ -12536,7 +12536,7 @@ M: Frank Rowand <frowand.list@gmail.com>
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L: devicetree@vger.kernel.org
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S: Maintained
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F: Documentation/devicetree/dynamic-resolution-notes.rst
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F: Documentation/devicetree/overlay-notes.txt
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F: Documentation/devicetree/overlay-notes.rst
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F: drivers/of/overlay.c
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F: drivers/of/resolver.c
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K: of_overlay_notifier_
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