From 80bf3ad51190dd7a52aea5767c1efad9ee30b82e Mon Sep 17 00:00:00 2001
From: Fiona Klute <fiona.klute@gmx.de>
Date: Mon, 30 Jun 2025 12:53:21 +0200
Subject: [PATCH] doc: move PXE README into usage documentation

This is only a reformatting, with a few grammar fixes (capitalization,
and a missing "is" and "be" added each).

Signed-off-by: Fiona Klute <fiona.klute@gmx.de>
Cc: Tom Rini <trini@konsulko.com>
---
 doc/README.pxe      | 292 --------------------------------------
 doc/usage/index.rst |   1 +
 doc/usage/pxe.rst   | 335 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 336 insertions(+), 292 deletions(-)
 delete mode 100644 doc/README.pxe
 create mode 100644 doc/usage/pxe.rst

diff --git a/doc/README.pxe b/doc/README.pxe
deleted file mode 100644
index ba189080e8c..00000000000
--- a/doc/README.pxe
+++ /dev/null
@@ -1,292 +0,0 @@
-SPDX-License-Identifier: GPL-2.0+
-/*
- * Copyright 2010-2011 Calxeda, Inc.
- */
-
-The 'pxe' commands provide a near subset of the functionality provided by
-the PXELINUX boot loader. This allows U-Boot based systems to be controlled
-remotely using the same PXE based techniques that many non U-Boot based servers
-use.
-
-Commands
-========
-
-pxe get
--------
-     syntax: pxe get
-
-     follows PXELINUX's rules for retrieving configuration files from a tftp
-     server, and supports a subset of PXELINUX's config file syntax.
-
-     Environment
-     -----------
-     'pxe get' requires two environment variables to be set:
-
-     pxefile_addr_r - should be set to a location in RAM large enough to hold
-     pxe files while they're being processed. Up to 16 config files may be
-     held in memory at once. The exact number and size of the files varies with
-     how the system is being used. A typical config file is a few hundred bytes
-     long.
-
-     bootfile,serverip - these two are typically set in the DHCP response
-     handler, and correspond to fields in the DHCP response.
-
-     'pxe get' optionally supports these two environment variables being set:
-
-     ethaddr - this is the standard MAC address for the ethernet adapter in use.
-     'pxe get' uses it to look for a configuration file specific to a system's
-     MAC address.
-
-     pxeuuid - this is a UUID in standard form using lower case hexadecimal
-     digits, for example, 550e8400-e29b-41d4-a716-446655440000. 'pxe get' uses
-     it to look for a configuration file based on the system's UUID.
-
-     File Paths
-     ----------
-     'pxe get' repeatedly tries to download config files until it either
-     successfully downloads one or runs out of paths to try. The order and
-     contents of paths it tries mirrors exactly that of PXELINUX - you can
-     read in more detail about it at:
-
-     http://syslinux.zytor.com/wiki/index.php/Doc/pxelinux
-
-pxe boot
---------
-     syntax: pxe boot [pxefile_addr_r]
-
-     Interprets a pxe file stored in memory.
-
-     pxefile_addr_r is an optional argument giving the location of the pxe file.
-     The file must be terminated with a NUL byte.
-
-     Environment
-     -----------
-     There are some environment variables that may need to be set, depending
-     on conditions.
-
-     pxefile_addr_r - if the optional argument pxefile_addr_r is not supplied,
-     an environment variable named pxefile_addr_r must be supplied. This is
-     typically the same value as is used for the 'pxe get' command.
-
-     bootfile - typically set in the DHCP response handler based on the
-     same field in the DHCP respone, this path is used to generate the base
-     directory that all other paths to files retrieved by 'pxe boot' will use.
-     If no bootfile is specified, paths used in pxe files will be used as is.
-
-     serverip - typically set in the DHCP response handler, this is the IP
-     address of the tftp server from which other files will be retrieved.
-
-     kernel_addr_r, initrd_addr_r - locations in RAM at which 'pxe boot' will
-     store the kernel(or FIT image) and initrd it retrieves from tftp. These
-     locations will be passed to the bootm command to boot the kernel. These
-     environment variables are required to be set.
-
-     fdt_addr_r - location in RAM at which 'pxe boot' will store the fdt blob it
-     retrieves from tftp. The retrieval is possible if 'fdt' label is defined in
-     pxe file and 'fdt_addr_r' is set. If retrieval is possible, 'fdt_addr_r'
-     will be passed to bootm command to boot the kernel.
-
-     fdt_addr - the location of a fdt blob. 'fdt_addr' will be passed to bootm
-     command if it is set and 'fdt_addr_r' is not passed to bootm command.
-
-     fdtoverlay_addr_r - location in RAM at which 'pxe boot' will temporarily store
-     fdt overlay(s) before applying them to the fdt blob stored at 'fdt_addr_r'.
-
-     pxe_label_override - override label to be used, if exists, instead of the
-     default label. This will allow consumers to choose a pxe label at
-     runtime instead of having to prompt the user. If "pxe_label_override" is set
-     but does not exist in the pxe menu, pxe would fallback to the default label if
-     given, and no failure is returned but rather a warning message.
-
-pxe file format
-===============
-The pxe file format is nearly a subset of the PXELINUX file format; see
-http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed of one line
-commands - global commands, and commands specific to labels. Lines begining
-with # are treated as comments. White space between and at the beginning of
-lines is ignored.
-
-The size of pxe files and the number of labels is only limited by the amount
-of RAM available to U-Boot. Memory for labels is dynamically allocated as
-they're parsed, and memory for pxe files is statically allocated, and its
-location is given by the pxefile_addr_r environment variable. The pxe code is
-not aware of the size of the pxefile memory and will outgrow it if pxe files
-are too large.
-
-Supported global commands
--------------------------
-Unrecognized commands are ignored.
-
-default <label>	    - the label named here is treated as the default and is
-		      the first label 'pxe boot' attempts to boot.
-
-fallback <label>    - the label named here is treated as a fallback option that
-		      may be attempted should it be detected that booting of
-		      the default has failed to complete, for example via
-		      U-Boot's boot count limit functionality.
-
-menu title <string> - sets a title for the menu of labels being displayed.
-
-menu include <path> - use tftp to retrieve the pxe file at <path>, which
-		      is then immediately parsed as if the start of its
-		      contents were the next line in the current file. nesting
-		      of include up to 16 files deep is supported.
-
-prompt <flag>	    - if 1, always prompt the user to enter a label to boot
-		      from. if 0, only prompt the user if timeout expires.
-
-timeout <num>	    - wait for user input for <num>/10 seconds before
-		      auto-booting a node.
-
-label <name>	    - begin a label definition. labels continue until
-		      a command not recognized as a label command is seen,
-		      or EOF is reached.
-
-Supported label commands
-------------------------
-labels end when a command not recognized as a label command is reached, or EOF.
-
-menu default	    - set this label as the default label to boot; this is
-		      the same behavior as the global default command but
-		      specified in a different way
-
-kernel <path>	    - if this label is chosen, use tftp to retrieve the kernel
-		      (or FIT image) at <path>. it will be stored at the address
-		      indicated in the kernel_addr_r environment variable, and
-		      that address will be passed to bootm to boot this kernel.
-		      For FIT image, The configuration specification can be
-		      appended to the file name, with the format:
-		        <path>#<conf>[#<extra-conf[#...]]
-		      It will passed to bootm with that address.
-		      (see: doc/uImage.FIT/command_syntax_extensions.txt)
-		      It useful for overlay selection in pxe file
-		      (see: doc/usage/fit/overlay-fdt-boot.rst).
-
-fdtoverlays <path> [...] - if this label is chosen, use tftp to retrieve the DT
-                      overlay(s) at <path>. it will be temporarily stored at the
-                      address indicated in the fdtoverlay_addr_r environment variable,
-                      and then applied in the load order to the fdt blob stored at the
-                      address indicated in the fdt_addr_r environment variable.
-
-devicetree-overlay <path> [...] - if this label is chosen, use tftp to retrieve the DT
-                      overlay(s) at <path>. it will be temporarily stored at the
-                      address indicated in the fdtoverlay_addr_r environment variable,
-                      and then applied in the load order to the fdt blob stored at the
-                      address indicated in the fdt_addr_r environment variable.
-                      Alias for fdtoverlays.
-
-kaslrseed           - set this label to request random number from hwrng as kaslr seed.
-
-append <string>	    - use <string> as the kernel command line when booting this
-		      label. Environment variable references like ${var} are
-		      substituted before boot.
-
-initrd <path>	    - if this label is chosen, use tftp to retrieve the initrd
-		      at <path>. it will be stored at the address indicated in
-		      the initrd_addr_r environment variable, and that address
-		      will be passed to bootm.
-		      For FIT image, the initrd can be provided with the same value than
-		      kernel, including configuration:
-		        <path>#<conf>[#<extra-conf[#...]]
-		      In this case, kernel_addr_r is passed to bootm.
-
-fdt <path>	    - if this label is chosen, use tftp to retrieve the fdt blob
-		      at <path>. it will be stored at the address indicated in
-		      the fdt_addr_r environment variable, and that address will
-		      be passed to bootm.
-		      For FIT image, the device tree can be provided with the same value
-		      than kernel, including configuration:
-		        <path>#<conf>[#<extra-conf[#...]]
-		      In this case, kernel_addr_r is passed to bootm.
-
-devicetree <path>   - if this label is chosen, use tftp to retrieve the fdt blob
-		      at <path>. it will be stored at the address indicated in
-		      the fdt_addr_r environment variable, and that address will
-		      be passed to bootm. Alias for fdt.
-
-fdtdir <path>	    - if this label is chosen, use tftp to retrieve a fdt blob
-		      relative to <path>. If the fdtfile environment variable
-		      is set, <path>/<fdtfile> is retrieved. Otherwise, the
-		      filename is generated from the soc and board environment
-		      variables, i.e. <path>/<soc>-<board>.dtb is retrieved.
-		      If the fdt command is specified, fdtdir is ignored.
-
-localboot <flag>    - Run the command defined by "localcmd" in the environment.
-		      <flag> is ignored and is only here to match the syntax of
-		      PXELINUX config files.
-
-Example
--------
-Here's a couple of example files to show how this works.
-
-------------/tftpboot/pxelinux.cfg/menus/base.menu-----------
-menu title Linux selections
-
-# This is the default label
-label install
-	menu label Default Install Image
-	kernel kernels/install.bin
-	append console=ttyAMA0,38400 debug earlyprintk
-	initrd initrds/uzInitrdDebInstall
-
-# Just another label
-label linux-2.6.38
-	kernel kernels/linux-2.6.38.bin
-	append root=/dev/sdb1
-
-# The locally installed kernel
-label local
-	menu label Locally installed kernel
-	append root=/dev/sdb1
-	localboot 1
--------------------------------------------------------------
-
-------------/tftpboot/pxelinux.cfg/default-------------------
-menu include pxelinux.cfg/menus/base.menu
-timeout 500
-
-default linux-2.6.38
--------------------------------------------------------------
-
-When a pxe client retrieves and boots the default pxe file,
-'pxe boot' will wait for user input for 5 seconds before booting
-the linux-2.6.38 label, which will cause /tftpboot/kernels/linux-2.6.38.bin
-to be downloaded, and boot with the command line "root=/dev/sdb1"
-
-Differences with PXELINUX
-=========================
-The biggest difference between U-Boot's pxe and PXELINUX is that since
-U-Boot's pxe support is written entirely in C, it can run on any platform
-with network support in U-Boot. Here are some other differences between
-PXELINUX and U-Boot's pxe support.
-
-- U-Boot's pxe does not support the PXELINUX DHCP option codes specified
-  in RFC 5071, but could be extended to do so.
-
-- when U-Boot's pxe fails to boot, it will return control to U-Boot,
-  allowing another command to run, other U-Boot command, instead of resetting
-  the machine like PXELINUX.
-
-- U-Boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it
-  only uses U-Boot.
-
-- U-Boot's pxe doesn't provide the full menu implementation that PXELINUX
-  does, only a simple text based menu using the commands described in
-  this README.	With PXELINUX, it's possible to have a graphical boot
-  menu, submenus, passwords, etc. U-Boot's pxe could be extended to support
-  a more robust menuing system like that of PXELINUX's.
-
-- U-Boot's pxe expects U-Boot uimg's as kernels.  Anything that would work
-  with the 'bootm' command in U-Boot could work with the 'pxe boot' command.
-
-- U-Boot's pxe only recognizes a single file on the initrd command line.  It
-  could be extended to support multiple.
-
-- in U-Boot's pxe, the localboot command doesn't necessarily cause a local
-  disk boot - it will do whatever is defined in the 'localcmd' env
-  variable. And since it doesn't support a full UNDI/PXE stack, the
-  type field is ignored.
-
-- the interactive prompt in U-Boot's pxe only allows you to choose a label
-  from the menu.  If you want to boot something not listed, you can ctrl+c
-  out of 'pxe boot' and use existing U-Boot commands to accomplish it.
diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index e9e0bd04e05..b9de87a6ed9 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -12,6 +12,7 @@ Use U-Boot
    fit/index
    netconsole
    partitions
+   pxe
    cmdline
    semihosting
    measured_boot
diff --git a/doc/usage/pxe.rst b/doc/usage/pxe.rst
new file mode 100644
index 00000000000..175938b942a
--- /dev/null
+++ b/doc/usage/pxe.rst
@@ -0,0 +1,335 @@
+.. SPDX-License-Identifier: GPL-2.0+
+   Copyright 2010-2011 Calxeda, Inc.
+
+PXE Boot
+========
+
+The ``pxe`` commands provide a near subset of the functionality
+provided by the PXELINUX boot loader. This allows U-Boot based systems
+to be controlled remotely using the same PXE based techniques that
+many non U-Boot based servers use.
+
+Commands
+--------
+
+``pxe get``
+        **syntax:** ``pxe get``
+
+	follows PXELINUX's rules for retrieving configuration files
+	from a tftp server, and supports a subset of PXELINUX's config
+	file syntax.
+
+	**Environment**
+
+	``pxe get`` requires two environment variables to be set:
+
+	``pxefile_addr_r`` - should be set to a location in RAM large
+	enough to hold pxe files while they're being processed. Up to
+	16 config files may be held in memory at once. The exact
+	number and size of the files varies with how the system is
+	being used. A typical config file is a few hundred bytes long.
+
+	``bootfile``, ``serverip`` - these two are typically set in
+	the DHCP response handler, and correspond to fields in the
+	DHCP response.
+
+	``pxe get`` optionally supports these two environment
+	variables being set:
+
+	``ethaddr`` - this is the standard MAC address for the
+	ethernet adapter in use. ``pxe get`` uses it to look for a
+	configuration file specific to a system's MAC address.
+
+	``pxeuuid`` - this is a UUID in standard form using lower case
+	hexadecimal digits, for example,
+	550e8400-e29b-41d4-a716-446655440000. ``pxe get`` uses it to
+	look for a configuration file based on the system's UUID.
+
+	**File Paths**
+
+	``pxe get`` repeatedly tries to download config files until it
+	either successfully downloads one or runs out of paths to
+	try. The order and contents of paths it tries mirrors exactly
+	that of PXELINUX - you can read in more detail about it at:
+
+	http://syslinux.zytor.com/wiki/index.php/Doc/pxelinux
+
+``pxe boot``
+        **syntax:** ``pxe boot [pxefile_addr_r]``
+
+	Interprets a pxe file stored in memory.
+
+	``pxefile_addr_r`` is an optional argument giving the location
+	of the pxe file. The file must be terminated with a NUL byte.
+
+	**Environment**
+
+	There are some environment variables that may need to be set,
+	depending on conditions.
+
+	``pxefile_addr_r`` - if the optional argument
+	``pxefile_addr_r`` is not supplied, an environment variable
+	named ``pxefile_addr_r`` must be supplied. This is typically
+	the same value as is used for the ``pxe get`` command.
+
+	``bootfile`` - typically set in the DHCP response handler
+	based on the same field in the DHCP respone, this path is used
+	to generate the base directory that all other paths to files
+	retrieved by ``pxe boot`` will use. If no bootfile is
+	specified, paths used in pxe files will be used as is.
+
+	``serverip`` - typically set in the DHCP response handler,
+	this is the IP address of the tftp server from which other
+	files will be retrieved.
+
+	``kernel_addr_r``, ``initrd_addr_r`` - locations in RAM at
+	which ``pxe boot`` will store the kernel(or FIT image) and
+	initrd it retrieves from tftp. These locations will be passed
+	to the bootm command to boot the kernel. These environment
+	variables are required to be set.
+
+	``fdt_addr_r`` - location in RAM at which ``pxe boot`` will
+	store the fdt blob it retrieves from tftp. The retrieval is
+	possible if ``fdt`` label is defined in pxe file and
+	``fdt_addr_r`` is set. If retrieval is possible,
+	``fdt_addr_r`` will be passed to bootm command to boot the
+	kernel.
+
+	``fdt_addr`` - the location of a fdt blob. ``fdt_addr`` will
+	be passed to ``bootm`` command if it is set and ``fdt_addr_r``
+	is not passed to bootm command.
+
+	``fdtoverlay_addr_r`` - location in RAM at which 'pxe boot'
+	will temporarily store fdt overlay(s) before applying them to
+	the fdt blob stored at ``fdt_addr_r``.
+
+	``pxe_label_override`` - override label to be used, if exists,
+	instead of the default label. This will allow consumers to
+	choose a pxe label at runtime instead of having to prompt the
+	user. If ``pxe_label_override`` is set but does not exist in
+	the pxe menu, pxe would fallback to the default label if
+	given, and no failure is returned but rather a warning
+	message.
+
+pxe file format
+---------------
+
+The pxe file format is nearly a subset of the PXELINUX file format;
+see http://syslinux.zytor.com/wiki/index.php/PXELINUX. It's composed
+of one line commands - global commands, and commands specific to
+labels. Lines beginning with # are treated as comments. White space
+between and at the beginning of lines is ignored.
+
+The size of pxe files and the number of labels is only limited by the amount
+of RAM available to U-Boot. Memory for labels is dynamically allocated as
+they're parsed, and memory for pxe files is statically allocated, and its
+location is given by the pxefile_addr_r environment variable. The pxe code is
+not aware of the size of the pxefile memory and will outgrow it if pxe files
+are too large.
+
+Supported global commands
+^^^^^^^^^^^^^^^^^^^^^^^^^
+Unrecognized commands are ignored.
+
+``default <label>``
+        The label named here is treated as the default and is the
+	first label 'pxe boot' attempts to boot.
+
+``fallback <label>``
+        The label named here is treated as a fallback option that may
+	be attempted should it be detected that booting of the default
+	has failed to complete, for example via U-Boot's boot count
+	limit functionality.
+
+``menu title <string>``
+        Sets a title for the menu of labels being displayed.
+
+``menu include <path>``
+        Use tftp to retrieve the pxe file at ``<path>``, which is then
+        immediately parsed as if the start of its contents were the
+        next line in the current file. nesting of include up to 16
+        files deep is supported.
+
+``prompt <flag>``
+        If 1, always prompt the user to enter a label to boot from. If
+        0, only prompt the user if timeout expires.
+
+``timeout <num>``
+        Wait for user input for <num>/10 seconds before auto-booting a
+        node.
+
+``label <name>``
+        Begin a label definition. Labels continue until a command not
+        recognized as a label command is seen, or EOF is reached.
+
+Supported label commands
+^^^^^^^^^^^^^^^^^^^^^^^^
+Labels end when a command not recognized as a label command is reached, or EOF.
+
+``menu default``
+        set this label as the default label to boot; this is the same
+        behavior as the global default command but specified in a
+        different way
+
+``kernel <path>``
+        If this label is chosen, use tftp to retrieve the kernel (or
+        FIT image) at ``<path>``. it will be stored at the address
+        indicated in the ``kernel_addr_r`` environment variable, and
+        that address will be passed to ``bootm`` to boot this
+        kernel. For FIT image, the configuration specification can be
+        appended to the file name, with the format:
+
+                ``<path>#<conf>[#<extra-conf[#...]]``
+
+        It will be passed to bootm with that address (see:
+        doc/uImage.FIT/command_syntax_extensions.txt). It is useful
+        for overlay selection in pxe file (see
+        :doc:`./fit/overlay-fdt-boot`).
+
+``fdtoverlays <path> [...]``
+        If this label is chosen, use tftp to retrieve the DT
+        overlay(s) at ``<path>``. It will be temporarily stored at the
+        address indicated in the ``fdtoverlay_addr_r`` environment
+        variable, and then applied in the load order to the fdt blob
+        stored at the address indicated in the ``fdt_addr_r``
+        environment variable.
+
+``devicetree-overlay <path> [...]``
+        if this label is chosen, use tftp to retrieve the DT
+        overlay(s) at ``<path>``. It will be temporarily stored at the
+        address indicated in the ``fdtoverlay_addr_r`` environment
+        variable, and then applied in the load order to the fdt blob
+        stored at the address indicated in the ``fdt_addr_r``
+        environment variable. Alias for fdtoverlays.
+
+``kaslrseed``
+        set this label to request random number from hwrng as kaslr seed.
+
+``append <string>``
+        Use ``<string>`` as the kernel command line when booting this
+        label. Environment variable references like ``${var}`` are
+        substituted before boot.
+
+``initrd <path>``
+        If this label is chosen, use tftp to retrieve the initrd at
+        ``<path>``. it will be stored at the address indicated in the
+        ``initrd_addr_r`` environment variable, and that address will
+        be passed to ``bootm``. For FIT image, the initrd can be
+        provided with the same value than kernel, including
+        configuration:
+
+                ``<path>#<conf>[#<extra-conf[#...]]``
+
+        In this case, ``kernel_addr_r`` is passed to ``bootm``.
+
+``fdt <path>``
+        If this label is chosen, use tftp to retrieve the fdt blob at
+        ``<path>``. It will be stored at the address indicated in the
+        ``fdt_addr_r`` environment variable, and that address will be
+        passed to ``bootm``. For FIT image, the device tree can be
+        provided with the same value than kernel, including
+        configuration:
+
+                ``<path>#<conf>[#<extra-conf[#...]]``
+
+        In this case, ``kernel_addr_r`` is passed to ``bootm``.
+
+``devicetree <path>``
+        If this label is chosen, use tftp to retrieve the fdt blob at
+        ``<path>``. it will be stored at the address indicated in the
+        ``fdt_addr_r`` environment variable, and that address will be
+        passed to ``bootm``. Alias for fdt.
+
+``fdtdir <path>``
+        If this label is chosen, use tftp to retrieve a fdt blob
+        relative to ``<path>``. If the ``fdtfile`` environment
+        variable is set, ``<path>/<fdtfile>`` is retrieved. Otherwise,
+        the filename is generated from the ``soc`` and ``board``
+        environment variables, i.e. ``<path>/<soc>-<board>.dtb`` is
+        retrieved. If the ``fdt`` command is specified, ``fdtdir`` is
+        ignored.
+
+``localboot <flag>``
+        Run the command defined by ``localcmd`` in the
+        environment. ``<flag>`` is ignored and is only here to match
+        the syntax of PXELINUX config files.
+
+Example
+-------
+Here's a couple of example files to show how this works.
+
+.. code-block::
+   :caption: /tftpboot/pxelinux.cfg/menus/base.menu
+
+   menu title Linux selections
+
+   # This is the default label
+   label install
+       menu label Default Install Image
+       kernel kernels/install.bin
+       append console=ttyAMA0,38400 debug earlyprintk
+       initrd initrds/uzInitrdDebInstall
+
+   # Just another label
+   label linux-2.6.38
+       kernel kernels/linux-2.6.38.bin
+       append root=/dev/sdb1
+
+   # The locally installed kernel
+   label local
+       menu label Locally installed kernel
+       append root=/dev/sdb1
+       localboot 1
+
+.. code-block::
+   :caption: /tftpboot/pxelinux.cfg/default
+
+   menu include pxelinux.cfg/menus/base.menu
+   timeout 500
+
+   default linux-2.6.38
+
+When a pxe client retrieves and boots the default pxe file, ``pxe
+boot`` will wait for user input for 5 seconds before booting the
+``linux-2.6.38`` label, which will cause
+``/tftpboot/kernels/linux-2.6.38.bin`` to be downloaded, and boot with
+the command line ``root=/dev/sdb1``
+
+Differences with PXELINUX
+-------------------------
+
+The biggest difference between U-Boot's pxe and PXELINUX is that since
+U-Boot's pxe support is written entirely in C, it can run on any platform
+with network support in U-Boot. Here are some other differences between
+PXELINUX and U-Boot's pxe support.
+
+- U-Boot's pxe does not support the PXELINUX DHCP option codes specified
+  in RFC 5071, but could be extended to do so.
+
+- when U-Boot's pxe fails to boot, it will return control to U-Boot,
+  allowing another command to run, other U-Boot command, instead of resetting
+  the machine like PXELINUX.
+
+- U-Boot's pxe doesn't rely on or provide an UNDI/PXE stack in memory, it
+  only uses U-Boot.
+
+- U-Boot's pxe doesn't provide the full menu implementation that PXELINUX
+  does, only a simple text based menu using the commands described in
+  this README. With PXELINUX, it's possible to have a graphical boot
+  menu, submenus, passwords, etc. U-Boot's pxe could be extended to support
+  a more robust menuing system like that of PXELINUX's.
+
+- U-Boot's pxe expects U-Boot uimg's as kernels.  Anything that would work
+  with the 'bootm' command in U-Boot could work with the 'pxe boot' command.
+
+- U-Boot's pxe only recognizes a single file on the initrd command line.  It
+  could be extended to support multiple.
+
+- in U-Boot's pxe, the localboot command doesn't necessarily cause a local
+  disk boot - it will do whatever is defined in the 'localcmd' env
+  variable. And since it doesn't support a full UNDI/PXE stack, the
+  type field is ignored.
+
+- the interactive prompt in U-Boot's pxe only allows you to choose a label
+  from the menu.  If you want to boot something not listed, you can ctrl+c
+  out of 'pxe boot' and use existing U-Boot commands to accomplish it.
-- 
2.47.2