[PATCH v4 18/22] Mark DISTRO_DEFAULTS as deprecated

[Simon Glass]

Standard boot has been in place for a while now. Quite a few problems
have been found and fixed. It seems like a good time to mark the
script-based approach as deprecated and encourage people to use standard
boot.

Update the DISTRO_DEFAULTS Kconfig to encourage people to move to
standard boot, which is able to boot Linux distributions automatically.

Add a short migration guide to make this easier.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

(no changes since v3)

Changes in v3:
- Drop extra newline and quote

Changes in v2:
- Mention in the DISTRO_DEFAULTS option that it is script-based
- Expand and rewrite the commit message
- Use the word 'Mark' instead of 'Make' to improve the English

 boot/Kconfig            |  6 +++++-
 doc/develop/bootstd.rst | 23 +++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/boot/Kconfig b/boot/Kconfig
index 4ebcf3109113..7ef44a26fb92 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -784,7 +784,7 @@ config SYS_BOOT_RAMDISK_HIGH
 endmenu		# Boot images
 
 config DISTRO_DEFAULTS
-	bool "Select defaults suitable for booting general purpose Linux distributions"
+	bool "(deprecated) Script-based booting of Linux distributions"
 	select BOOT_DEFAULTS
 	select AUTO_COMPLETE
 	select CMDLINE_EDITING
@@ -792,6 +792,10 @@ config DISTRO_DEFAULTS
 	select HUSH_PARSER
 	select SYS_LONGHELP
 	help
+	  Note: These scripts have been replaced by Standard Boot. Do not use
+	  them on new boards. See 'Migrating from distro_boot' at
+	  doc/develop/bootstd.rst
+
 	  Select this to enable various options and commands which are suitable
 	  for building u-boot for booting general purpose Linux distributions.
 
diff --git a/doc/develop/bootstd.rst b/doc/develop/bootstd.rst
index e8b90752f083..6172dc906bde 100644
--- a/doc/develop/bootstd.rst
+++ b/doc/develop/bootstd.rst
@@ -464,6 +464,28 @@ ready    File was loaded and is ready for use. In this state the bootflow is
 =======  =======================================================================
 
 
+Migrating from distro_boot
+--------------------------
+
+To migrate from distro_boot:
+
+#. Update your board header files to remove the BOOTENV and BOOT_TARGET_xxx
+   defines. Standard boot finds available boot devices automatically.
+
+#. Remove the "boot_targets" variable unless you need it. Standard boot uses a
+   default order from fastest to slowest, which generally matches the order used
+   by boards.
+
+#. Make sure that CONFIG_BOOTSTD_DEFAULTS is enabled by your board, so it can
+   boot common Linux distributions.
+
+An example patch is at migrate_patch_.
+
+If you are using custom boot scripts for your board, consider creating your
+own bootmeth to hold the logic. There are various examples at
+`boot/bootmeth_...`.
+
+
 Theory of operation
 -------------------
 
@@ -775,3 +797,4 @@ Other ideas:
 .. _BootLoaderSpec: http://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/
 .. _distro_boot: https://github.com/u-boot/u-boot/blob/master/boot/distro.c
 .. _bootflow_h: https://github.com/u-boot/u-boot/blob/master/include/bootflow.h
+.. _migrate_patch: https://patchwork.ozlabs.org/project/uboot/patch/20230727215433.578830-2-sjg@chromium.org/
-- 
2.42.0.283.g2d96d420d3-goog