--- wikisrc/ports/evbarm/raspberry_pi.mdwn	2020/09/05 12:54:33	1.130
+++ wikisrc/ports/evbarm/raspberry_pi.mdwn	2020/10/15 19:27:27	1.131
@@ -203,23 +203,44 @@ The program vcgencmd, referenced in the 
 
 ## Updating the kernel
 
- - Build a new kernel, e.g. using build.sh. It will tell you where the ELF version of the kernel is, e.g.
-
+ - Run uname -a to determine the name of the config of your current kernel.  For NetBSD <= 8, one ran RPI or RPI2.  For NetBSD >=9, one uses GENERIC.
+ - Build a new kernel, e.g. using build.sh. Ideally, run "build.sh release" and look in releasedir/binary/kernels.  If building just a kernel, it will tell you where the ELF version of the kernel is, e.g.
          ...
-         Kernels built from RPI2:
-          /Users/feyrer/work/NetBSD/cvs/src-current/obj.evbarm-Darwin-XXX/sys/arch/evbarm/compile/RPI2/netbsd
+         Kernels built from GENERIC:
+          /Users/feyrer/work/NetBSD/cvs/src-current/obj.evbarm-Darwin-XXX/sys/arch/evbarm/compile/GENERIC/netbsd
          ...
-
- - Besides the "netbsd" kernel in ELF format, there is also a "netbsd.img" (for current) or "netbsd.bin" (for 7 and 8) kernel that is in a format that the Raspberry can boot.
+ - There are multiple kernel formats produced by a release build, for use with different boot loader schemes..  For GENERIC:
+   - netbsd-GENERIC: A normal kernel in ELF format.
+   - netbsd-GENERIC.img: In NetBSD >= 9, formatted for the RPI bootloader.
+   - netbsd-GENERIC.bin: In NetBSD <= 8, formatted for the RPI bootloader.  In NetBSD >= 9, ??????  In NetBSD 9, this kernel WILL NOT boot.
+   - netbsd-GENERIC.ub: A kernel in uboot format.
  - Depending on your hardware version, copy this either to /boot/kernel.img (First generation Pi, Pi Zero hardware) or to /boot/kernel7.img (Pi 2, Pi 3 hardware)
  - reboot
 
 \todo Explain if updating firmware is necessary when e.g. moving from 8 to 9, or 9 to current.
 
+## Updating dtb files
+
+(This is harder than it should be.)
+Build a release.  gunzip the armv7.img, vnconfig it, and mount the MSDOS partition (e) e.g. on /mnt.  Copy the dtb files from /mnt/*.dtb to /boot, and from /mnt/dtb/*.dtb to /mnt/dtb.
+
+It seems that some systems, including RPI, require dtb files in /boot, and some expect  them in /boot/dtb.
+
+\todo Explain how one is supposed to be able to update these from the dtb files in releasedir/binary/kernel, or fix it to have the same structure.
+
 ## Updating the firmware
 
+It is highly likely that running NetBSD from a given branch X with firmware from a branch Y < X will not go well.  It is unclear if firmware from a branch Y > X will work.   It is standard practice to use firmware from the right branch.
+
 A section below describes the process of updating NetBSD's copy of the firmware from upstream, with testing, by NetBSD developers.  This section is about updating a system's firmware from the firmware in a version of NetBSD.
 
+(Updating the firmware is harder than it should be.)
+Build a release.  gunzip the armv7.img, vnconfig it, and mount the MSDOS partition (e) e.g. on /mnt.  Copy files from that to /boot that have changes, carefully.
+
+Relevant files include bootcode.bin, start.elf and start_cd.elf.
+
+Compare cmdline.txt, but beware that just overwriting it will lose customizations like using the serial console instead of the framebuffer.
+
 \todo Explain where the firmware is in the source tree, and note that it is not in the installed system image (such as /usr/mdec).  Explain how to update a system (presumably /boot) from either an installed system's new firmware files, or the source tree.  Explain any particular cautions.
 
 \todo Explain if using updated firmware from one branch (e.g. netbsd-current) on a system using a different branch (e.g. netbsd-8) is safe.  Explain if pullups are done to release branches with new firmware.