--- wikisrc/ports/evbarm/raspberry_pi.mdwn	2020/10/15 19:58:19	1.135
+++ wikisrc/ports/evbarm/raspberry_pi.mdwn	2020/10/16 17:35:05	1.138
@@ -174,8 +174,18 @@ every few weeks.
 
  - <https://github.com/ebijun/NetBSD/blob/master/RPI/RPIimage/Image/README>
 
-## Configuring 802.11
+## Boot Process
+
+https://www.raspberrypi.org/documentation/configuration/config-txt/boot.md
+
+### DTBs
 
+Note that generally, a single dtb is loaded.  On NetBSD 9, the dtb
+file for the system is loaded by the bootloader (in flash).
+
+The RPI bootloader looks for a magic string in a trailer after the kernel to determine if it should use DTB support (the new normal) or something called ATAG (apparently the old way).  See https://github.com/raspberrypi/linux/commit/2367d8a42e2717d8d15a39a9085cc2909fae033a#diff-8f088aca645d10d79b594d58db4136f3e09caee077fe373bb08f02f2040900a9 for more information.
+
+## Configuring 802.11
 After installation, the Ethernet will function as on any other NetBSD system; simply enable dhcpcd or configure a static address.  USB WiFi devices will also function as on any other NetBSD system; in addition to dhcpcd or static, configure and enable wpa_supplicant.
 
 Note that the built-in WiFi in the RPI3 is not yet supported.   USB WiFi interfaces (that work on NetBSD in general) should all work.  In particular, the following are known to work:
@@ -218,8 +228,14 @@ The program vcgencmd, referenced in the 
 
 ## Updating dtb files
 
+### NetBSD 8
+
+On NetBSD 8, dtb files are not used. (\todo Really?)
+
+### NetBSD 9
+
 (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/foo.dtb to /boot, and from /mnt/dtb/foo.dtb to /mnt/dtb.
+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/foo.dtb to /boot, and from /mnt/dtb/foo.dtb to /boot/dtb.
 
 It seems that some systems, including RPI, require dtb files in /boot, and some expect them in /boot/dtb.
 
@@ -227,6 +243,10 @@ It seems that some systems, including RP
 
 \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.
 
+### NetBSD current
+
+When updating, ensure that /boot is mounted and that you unpack the dtb set.
+
 ## 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.