[U-Boot-Users] RFC: new bootm syntax v2

[Bartlomiej Sieka]

Bartlomiej Sieka wrote:
[...]
> As part of adding support for the new uImage format, bootm command will
> be reworked quite a bit. Below is a note that summarizes bootm usage
> scenarios (present and planned), and defines extensions to bootm
> arguments' syntax. The note, or its portions, can be later on added to
> the tree as documentation.

Here's a revised note, with the following changes from the first version:
- addressed Wolfgang's comments posted to the list
- dropped support for standalone applications from bootm

Looking forward to any comments, questions, etc.

Thanks,
Bartlomiej



New syntax for bootm (v2)
=========================

As part of adding support for new uImage format, bootm command (and other
commands as well) will 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 both current and future bootm usage scenarios, and then
introduces new argument syntax.


bootm usage scenarios
---------------------

Below is a summary of bootm usage scenarios, focused on booting a PowerPC
Linux kernel. Some of the scenarios exist and are supported already, some
will be extended/added along with the new uImage format. The purpose of
the following list is to document a complete list of supported bootm
usages.

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.


1.  bootm               boot image at the current address, equivalent to 
2,3,8

Old uImage:
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> */

New uImage:
8.  bootm <addr1>
9.  bootm [<addr1>]:<subimg1>
10. bootm [<addr1>]#<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>


Ad. 1. This is equivalent to cases 2,3,8, depending on the type of image
at the current image address.
- boot method: see cases 2,3,8

Ad. 2. Boot kernel image located at <addr1>.ddr1> with initrd loaded 
with ramdisk <subimg2> from the image
at <addr2>.
- boot method: non-FDT

Ad. 12. 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

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

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>.
- 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


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
CFG_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, is
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 at 1
Last command is equivalent to:
bootm 200000:kernel at 1

tftp 200000 /tftpboot/uImage
bootm 400000:kernel at 1 :ramdisk at 1
Last command is equivalent to:
bootm 400000:kernel at 1 400000:ramdisk at 1

tftp 200000 /tftpboot/uImage
bootm :kernel at 1 400000:ramdisk at 1 :fdt at 1
Last command is equivalent to:
bootm 200000:kernel at 1 400000:ramdisk at 1 400000:fdt at 1