From 64a1446bd09ec58ab259c9ec2b3160ac604b734f Mon Sep 17 00:00:00 2001
From: Simon Glass <sjg@chromium.org>
Date: Wed, 17 Jul 2024 09:30:55 +0100
Subject: [PATCH] doc: Add a description for bootmeth_pxe
Add documentation for the pxe bootmeth.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
---
doc/develop/bootstd/extlinux.rst | 3 ++-
doc/develop/bootstd/index.rst | 1 +
doc/develop/bootstd/overview.rst | 2 +-
doc/develop/bootstd/pxelinux.rst | 27 +++++++++++++++++++++++++++
4 files changed, 31 insertions(+), 2 deletions(-)
create mode 100644 doc/develop/bootstd/pxelinux.rst
diff --git a/doc/develop/bootstd/extlinux.rst b/doc/develop/bootstd/extlinux.rst
index 46e9ad9eea..bf27dc57aa 100644
--- a/doc/develop/bootstd/extlinux.rst
+++ b/doc/develop/bootstd/extlinux.rst
@@ -14,7 +14,8 @@ under the `boot/` subdirectory. This list of prefixes (``{"/", "/boot"}`` by
default) can be selected with the `filename-prefixes` property in the bootstd
device.
-Note that the PXE bootmeth uses the same file format, but in a network context.
+Note that the :doc:`pxelinux` uses the same file format, but in a
+network context.
When invoked on a bootdev, this bootmeth searches for the file and creates a
bootflow if found.
diff --git a/doc/develop/bootstd/index.rst b/doc/develop/bootstd/index.rst
index 5bbb3d633a..5052afe448 100644
--- a/doc/develop/bootstd/index.rst
+++ b/doc/develop/bootstd/index.rst
@@ -8,3 +8,4 @@ Standard Boot
overview
extlinux
+ pxelinux
diff --git a/doc/develop/bootstd/overview.rst b/doc/develop/bootstd/overview.rst
index 26b798596c..6afa1c2961 100644
--- a/doc/develop/bootstd/overview.rst
+++ b/doc/develop/bootstd/overview.rst
@@ -417,7 +417,7 @@ Available bootmeth drivers
Bootmeth drivers are provided for booting from various media:
- :doc:`extlinux / syslinux <extlinux>` boot from a storage device
- - extlinux boot from a network (PXE)
+ - :doc:`extlinux / syslinux <extlinux>` boot from a network (PXE)
- U-Boot scripts from disk, network or SPI flash
- EFI boot using bootefi from disk
- VBE
diff --git a/doc/develop/bootstd/pxelinux.rst b/doc/develop/bootstd/pxelinux.rst
new file mode 100644
index 0000000000..c4b7fbb4c9
--- /dev/null
+++ b/doc/develop/bootstd/pxelinux.rst
@@ -0,0 +1,27 @@
+.. SPDX-License-Identifier: GPL-2.0+:
+
+PXE Bootmeth
+============
+
+PXE (Preboot eXecution-Environment) provides a way to boot an operating system
+over a network interface. The PXE bootmeth supports PXELINUX and allows U-Boot to
+provide a menu of possible Operating Systems from which the user can choose.
+
+U-Boot includes a parser for the `extlinux.conf` file described
+`here <https://uapi-group.org/specifications/specs/boot_loader_specification>`_.
+It consists primarily of a list of named operating systems along with the
+kernel, initial ramdisk and other settings. The file is retrieved from a network
+server using the TFTP protocol.
+
+When invoked on a bootdev, this bootmeth searches for the file and creates a
+bootflow if found. See
+`PXELINUX <https://wiki.syslinux.org/wiki/index.php?title=PXELINUX>`_ for
+a full description of the search procedure.
+
+When the bootflow is booted, the bootmeth calls ``pxe_setup_ctx()`` to set up
+the context, then ``pxe_process()`` to process the file. Depending on the
+contents, this may boot an Operating System or provide a list of options to the
+user, perhaps with a timeout.
+
+The compatible string "u-boot,extlinux-pxe" is used for the driver. It is
+present if `CONFIG_BOOTMETH_EXTLINUX_PXE` is enabled.
--
2.39.5