[PATCH v2 14/14] doc: Improve documentation for the bootm command
Simon Glass
sjg at chromium.org
Fri Jun 23 14:22:14 CEST 2023
Reformat and rewrite the documentation for this command.
This is a complicated command, so further improvements are welcome.
Signed-off-by: Simon Glass <sjg at chromium.org>
---
(no changes since v1)
doc/usage/cmd/bootm.rst | 327 ++++++++++++++++++++++++----------------
doc/usage/fit/index.rst | 1 -
doc/usage/index.rst | 1 +
3 files changed, 201 insertions(+), 128 deletions(-)
diff --git a/doc/usage/cmd/bootm.rst b/doc/usage/cmd/bootm.rst
index 65b7891c8a69..a7e5f6ce69ab 100644
--- a/doc/usage/cmd/bootm.rst
+++ b/doc/usage/cmd/bootm.rst
@@ -1,161 +1,267 @@
.. SPDX-License-Identifier: GPL-2.0+
-Command syntax extensions for the new uImage format
-===================================================
+bootm command
+=============
-Author: Bartlomiej Sieka <tur at semihalf.com>
+Synopsis
+--------
-With the introduction of the new uImage format, bootm command (and other
-commands as well) have to understand new syntax of the arguments. This is
-necessary in order to specify objects contained in the new uImage, on which
-bootm has to operate. This note attempts to first summarize bootm usage
-scenarios, and then introduces new argument syntax.
+::
+ bootm [fit_addr]#<conf>[#extra-conf]
+ bootm [[fit_addr]:<os_subimg>] [[<fit_addr2>]:<rd_subimg2>] [[<fit_addr3>]:<fdt_subimg>]
-bootm usage scenarios
----------------------
+ bootm <addr1> [[<addr2> [<addr3>]] # Legacy boot
-Below is a summary of bootm usage scenarios, focused on booting a PowerPC
-Linux kernel. The purpose of the following list is to document a complete list
-of supported bootm usages.
+Description
+-----------
-Note: U-Boot supports two methods of booting a PowerPC Linux kernel: old way,
-i.e., without passing the Flattened Device Tree (FDT), and new way, where the
-kernel is passed a pointer to the FDT. The boot method is indicated for each
-scenario::
+The *bootm* command is used to boot an Operating System. It has a large number
+of options depending on what needs to be booted.
- 1. bootm boot image at the current address, equivalent to 2,3,8
+Note that the second form supports the first and/or second arguments to be
+omitted by using a hyphen '-' instead.
-Old uImage::
+fit_addr / fit_addr2 / fit_addr3
+ address of FIT to boot, defaults to CONFIG_SYS_LOAD_ADDR. See notes below.
- 2. bootm <addr1> /* single image at <addr1> */
- 3. bootm <addr1> /* multi-image at <addr1> */
- 4. bootm <addr1> - /* multi-image at <addr1> */
- 5. bootm <addr1> <addr2> /* single image at <addr1> */
- 6. bootm <addr1> <addr2> <addr3> /* single image at <addr1> */
- 7. bootm <addr1> - <addr3> /* single image at <addr1> */
+conf
+ configuration unit to boot (must be preceded by hash '#')
-New uImage::
+extra-conf
+ extra configuration to boot. This is supported only for additional
+ devicetree overlays to apply on the base device tree supplied by the first
+ configuration unit.
- 8. bootm <addr1>
- 9. bootm [<addr1>]:<subimg1>
- 10. bootm [<addr1>]#<conf>[#<extra-conf[#...]]
- 11. bootm [<addr1>]:<subimg1> [<addr2>]:<subimg2>
- 12. bootm [<addr1>]:<subimg1> [<addr2>]:<subimg2> [<addr3>]:<subimg3>
- 13. bootm [<addr1>]:<subimg1> [<addr2>]:<subimg2> <addr3>
- 14. bootm [<addr1>]:<subimg1> - [<addr3>]:<subimg3>
- 15. bootm [<addr1>]:<subimg1> - <addr3>
+os_subimg
+ OS sub-image to boot (must be preceded by colon ':')
+
+rd_subimg
+ ramdisk sub-image to boot. Use a hyphen '-' if there is no ramdisk but an
+ FDT is needed.
+
+fdt_subimg
+ FDT sub-image to boot
+
+See below for legacy boot. Booting using :doc:`../fit/index` is recommended.
+
+Note on current image address
+-----------------------------
+
+When bootm is called without arguments, the image at current image address is
+booted. The current image address is the address set most recently by a load
+command, etc, and is by default equal to CONFIG_SYS_LOAD_ADDR. For example,
+consider the following commands::
+
+ tftp 200000 /tftpboot/kernel
+ bootm
+ # Last command is equivalent to:
+ # bootm 200000
+
+As shown above, with FIT the address portion of any argument
+can be omitted. If <addr3> is omitted, then it is assumed that image at
+<addr2> should be used. Similarly, when <addr2> is omitted, it is assumed that
+image at <addr1> should be used. If <addr1> is omitted, it is assumed that the
+current image address is to be used. For example, consider the following
+commands::
+
+ tftp 200000 /tftpboot/uImage
+ bootm :kernel-1
+ # Last command is equivalent to:
+ # bootm 200000:kernel-1
+
+ tftp 200000 /tftpboot/uImage
+ bootm 400000:kernel-1 :ramdisk-1
+ # Last command is equivalent to:
+ # bootm 400000:kernel-1 400000:ramdisk-1
+
+ tftp 200000 /tftpboot/uImage
+ bootm :kernel-1 400000:ramdisk-1 :fdt-1
+ # Last command is equivalent to:
+ # bootm 200000:kernel-1 400000:ramdisk-1 400000:fdt-1
+
+
+Legacy boot
+-----------
+
+U-Boot supports a legacy image format, enabled by `CONFIG_LEGACY_IMAGE_FORMAT`.
+This is not recommended as it is quite limited and insecure. Use
+:doc:`../fit/index` instead. It is documented here for old boards which still
+use it.
+
+Arguments are:
+
+addr1
+ address of legacy image to boot. If the image includes a second component
+ (ramdisk) it is used as well, unless the second parameter is hyphen '-'.
+
+addr2
+ address of legacy image to use as ramdisk
-Ad. 1. This is equivalent to cases 2,3,8, depending on the type of image at
+addr3
+ address of legacy image to use as FDT
+
+
+Example syntax
+--------------
+
+This section provides various examples of possible usage::
+
+ 1. bootm /* boot image at the current address, equivalent to 2,3,8 */
+
+This is equivalent to cases 2, 3 or 8, depending on the type of image at
the current image address.
-- boot method: see cases 2,3,8
+Boot method: see cases 2,3,8
+
+Legacy uImage syntax
+~~~~~~~~~~~~~~~~~~~~
-Ad. 2. Boot kernel image located at <addr1>.
+::
+
+ 2. bootm <addr1> /* single image at <addr1> */
-- boot method: non-FDT
+Boot kernel image located at <addr1>.
-Ad. 3. First and second components of the image at <addr1> are assumed to be a
+Boot method: non-FDT
+
+::
+
+ 3. bootm <addr1> /* multi-image at <addr1> */
+
+First and second components of the image at <addr1> are assumed to be a
kernel and a ramdisk, respectively. The kernel is booted with initrd loaded
with the ramdisk from the image.
-- boot method: depends on the number of components at <addr1>, and on whether
- U-Boot is compiled with OF support::
+Boot method: depends on the number of components at <addr1>, and on whether
+U-Boot is compiled with OF support, which it should be.
- ======================================================================
- | 2 components | 3 components|
- | (kernel, initrd) | (kernel, initrd, fdt) |
- ======================================================================
- #ifdef CONFIG_OF_* | non-FDT | FDT |
- #ifndef CONFIG_OF_* | non-FDT | non-FDT |
- ======================================================================
+ ==================== ======================== ========================
+ Configuration 2 components 3 components
+ (kernel, initrd) (kernel, initrd, fdt)
+ ==================== ======================== ========================
+ #ifdef CONFIG_OF_* non-FDT FDT
+ #ifndef CONFIG_OF_* non-FDT non-FDT
+ ==================== ======================== ========================
+
+::
+
+ 4. bootm <addr1> - /* multi-image at <addr1> */
-Ad. 4. Similar to case 3, but the kernel is booted without initrd. Second
+Similar to case 3, but the kernel is booted without initrd. Second
component of the multi-image is irrelevant (it can be a dummy, 1-byte file).
-- boot method: see case 3
+Boot method: see case 3
-Ad. 5. Boot kernel image located at <addr1> with initrd loaded with ramdisk
+::
+
+ 5. bootm <addr1> <addr2> /* single image at <addr1> */
+
+Boot kernel image located at <addr1> with initrd loaded with ramdisk
from the image at <addr2>.
-- boot method: non-FDT
+Boot method: non-FDT
+
+::
-Ad. 6. <addr1> is the address of a kernel image, <addr2> is the address of a
+ 6. bootm <addr1> <addr2> <addr3> /* single image at <addr1> */
+
+<addr1> is the address of a kernel image, <addr2> is the address of a
ramdisk image, and <addr3> is the address of a FDT binary blob. Kernel is
booted with initrd loaded with ramdisk from the image at <addr2>.
-- boot method: FDT
+Boot method: FDT
+
+::
+
+ 7. bootm <addr1> - <addr3> /* single image at <addr1> */
-Ad. 7. <addr1> is the address of a kernel image and <addr3> is the address of
+<addr1> is the address of a kernel image and <addr3> is the address of
a FDT binary blob. Kernel is booted without initrd.
-- boot method: FDT
+Boot method: FDT
+
+FIT syntax
+~~~~~~~~~~
+
+::
+
+ 8. bootm <addr1>
-Ad. 8. Image at <addr1> is assumed to contain a default configuration, which
+Image at <addr1> is assumed to contain a default configuration, which
is booted.
-- boot method: FDT or non-FDT, depending on whether the default configuration
- defines FDT
+Boot method: FDT or non-FDT, depending on whether the default configuration
+defines FDT
+
+::
+
+ 9. bootm [<addr1>]:<subimg1>
-Ad. 9. Similar to case 2: boot kernel stored in <subimg1> from the image at
+Similar to case 2: boot kernel stored in <subimg1> from the image at
address <addr1>.
-- boot method: non-FDT
+Boot method: non-FDT
-Ad. 10. Boot configuration <conf> from the image at <addr1>.
+::
-- boot method: FDT or non-FDT, depending on whether the configuration given
- defines FDT
+ 10. bootm [<addr1>]#<conf>[#<extra-conf[#...]]
+
+Boot configuration <conf> from the image at <addr1>.
+
+Boot method: FDT or non-FDT, depending on whether the configuration given
+defines FDT
+
+::
-Ad. 11. Equivalent to case 5: boot kernel stored in <subimg1> from the image
+ 11. bootm [<addr1>]:<subimg1> [<addr2>]:<subimg2>
+
+Equivalent to case 5: boot kernel stored in <subimg1> from the image
at <addr1> with initrd loaded with ramdisk <subimg2> from the image at
<addr2>.
-- boot method: non-FDT
+Boot method: non-FDT
-Ad. 12. Equivalent to case 6: boot kernel stored in <subimg1> from the image
+::
+
+ 12. bootm [<addr1>]:<subimg1> [<addr2>]:<subimg2> [<addr3>]:<subimg3>
+
+Equivalent to case 6: boot kernel stored in <subimg1> from the image
at <addr1> with initrd loaded with ramdisk <subimg2> from the image at
<addr2>, and pass FDT blob <subimg3> from the image at <addr3>.
-- boot method: FDT
+Boot method: FDT
-Ad. 13. Similar to case 12, the difference being that <addr3> is the address
-of FDT binary blob that is to be passed to the kernel.
+::
-- boot method: FDT
+ 13. bootm [<addr1>]:<subimg1> [<addr2>]:<subimg2> <addr3>
-Ad. 14. Equivalent to case 7: boot kernel stored in <subimg1> from the image
-at <addr1>, without initrd, and pass FDT blob <subimg3> from the image at
-<addr3>.
+Similar to case 12, the difference being that <addr3> is the address
+of FDT binary blob that is to be passed to the kernel.
-- boot method: FDT
+Boot method: FDT
-Ad. 15. Similar to case 14, the difference being that <addr3> is the address
-of the FDT binary blob that is to be passed to the kernel.
+::
-- boot method: FDT
+ 14. bootm [<addr1>]:<subimg1> - [<addr3>]:<subimg3>
+Equivalent to case 7: boot kernel stored in <subimg1> from the image
+at <addr1>, without initrd, and pass FDT blob <subimg3> from the image at
+<addr3>.
-New uImage argument syntax
---------------------------
+Boot method: FDT
-New uImage support introduces two new forms for bootm arguments, with the
-following syntax:
+ 15. bootm [<addr1>]:<subimg1> - <addr3>
-new uImage sub-image specification
- <addr>:<sub-image unit_name>
+Similar to case 14, the difference being that <addr3> is the address
+of the FDT binary blob that is to be passed to the kernel.
-new uImage configuration specification
- <addr>#<configuration unit_name>
+Boot method: FDT
-new uImage configuration specification with extra configuration components
- <addr>#<configuration unit_name>[#<extra configuration unit_name>[#..]]
-The extra configuration currently is supported only for additional device tree
-overlays to apply on the base device tree supplied by the first configuration
-unit.
-Examples:
+Example
+-------
boot kernel "kernel-1" stored in a new uImage located at 200000::
@@ -190,38 +296,5 @@ same new uImage::
bootm 200000:kernel-2 - 200000:fdt-1
-
-Note on current image address
------------------------------
-
-When bootm is called without arguments, the image at current image address is
-booted. The current image address is the address set most recently by a load
-command, etc, and is by default equal to CONFIG_SYS_LOAD_ADDR. For example, consider
-the following commands::
-
- tftp 200000 /tftpboot/kernel
- bootm
- Last command is equivalent to:
- bootm 200000
-
-In case of the new uImage argument syntax, the address portion of any argument
-can be omitted. If <addr3> is omitted, then it is assumed that image at
-<addr2> should be used. Similarly, when <addr2> is omitted, it is assumed that
-image at <addr1> should be used. If <addr1> is omitted, it is assumed that the
-current image address is to be used. For example, consider the following
-commands::
-
- tftp 200000 /tftpboot/uImage
- bootm :kernel-1
- Last command is equivalent to:
- bootm 200000:kernel-1
-
- tftp 200000 /tftpboot/uImage
- bootm 400000:kernel-1 :ramdisk-1
- Last command is equivalent to:
- bootm 400000:kernel-1 400000:ramdisk-1
-
- tftp 200000 /tftpboot/uImage
- bootm :kernel-1 400000:ramdisk-1 :fdt-1
- Last command is equivalent to:
- bootm 200000:kernel-1 400000:ramdisk-1 400000:fdt-1
+.. sectionauthor:: Bartlomiej Sieka <tur at semihalf.com>
+.. sectionauthor:: Simon Glass <sjg at chromium.org>
diff --git a/doc/usage/fit/index.rst b/doc/usage/fit/index.rst
index 92998e724c28..bd25bd30b284 100644
--- a/doc/usage/fit/index.rst
+++ b/doc/usage/fit/index.rst
@@ -17,4 +17,3 @@ doc/uImage.FIT
verified-boot
beaglebone_vboot
overlay-fdt-boot
- command_syntax_extensions
diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index e1fe284b38c1..98dd8614fe53 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -31,6 +31,7 @@ Shell commands
cmd/bootefi
cmd/bootflow
cmd/booti
+ cmd/bootm
cmd/bootmenu
cmd/bootmeth
cmd/button
--
2.41.0.162.gfafddb0af9-goog
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