1/// notes about altboot ///
2
3$NetBSD: README.altboot,v 1.1 2011/01/23 01:05:30 nisimura Exp $
4
5Altboot is a functional bridge to fill the gap between a NAS product
6custom bootloader and the NetBSD kernel startup environment.  Altboot
7irons out and rectifies erroneously configured HW by product
8bootloaders and prepares a sane runtime better suited for booting
9NetBSD kernels.
10
11- provides the foundation of a fast NetBSD porting cycle with functionalities
12  product bootloaders don't have.
13- facilitates a flexible and clean NetBSD implementation tailoured
14  to target HW in detail, minimizing bumpy adjustments and hacks in
15  locore asm and machdeps in very early kernel startup stage.
16- levels out differences among similar-but-not-the-same porting
17  targets to make it possible having common NetBSD kernels for them.
18- builds and hands a bootinfo list to the NetBSD kernel.
19
20Altboot is known working on two models.
21- KuroBox with a popular U-Boot as the replacement of vendor proprietary
22
23   U-Boot 1.1.4 LiSt 2.1.0 (Sep 21 2006 - 00:22:56) LinkStation / KuroBox
24
25- Synology 101g+ with vendor custom PPCboot
26
27   PPCBoot 2.0.0 (Mar  1 2005 - 15:31:41)
28
29The standard use of altboot is to invoke it with a short script from
30U-Boot/PPCboot, where the altboot image is stored in an unoccupied 128KB
31section of the target's HW NOR flash.  Combined with standard
32U-Boot/PPCboot functions, it is possible to boot a NetBSD kernel off
33it right after power-on, without the help of manual intervention.  Note
34that the original U-Boot/PPCboot still remains useful and altboot works
35as a functional extension for them.
36
37Altboot hands the following bootinfo records to the NetBSD/sandpoint
38kernel.
39- processor clock tick value driving MPC8241/8245.
40- serial console selection.
41- booted kernel filename and which device it was fetched from.
42- Ethernet MAC address, if target HW lacks SEEPROM to store a unit unique
43  value.
44- product family indication.
45- preloaded kernel module names (under development).
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