Some armv7 machines are shipped with linux images that run USB OTG ports

in client mode and provide serial access to a getty and networking.

Make it clear that a real serial console that can interact with the
firmware is required.

Suggested by and wording tweaks from ian@

diff --git a/distrib/notes/armv7/prep b/distrib/notes/armv7/prep
index c9738dd..4743c22 100644 (file)
--- a/distrib/notes/armv7/prep
+++ b/distrib/notes/armv7/prep
@@ -1,7 +1,13 @@
-dnl    $OpenBSD: prep,v 1.9 2016/07/09 07:19:52 jsg Exp $
+dnl    $OpenBSD: prep,v 1.10 2016/07/23 16:22:17 jsg Exp $
 Please be aware that OpenBSD support for this platform is far from
 complete.
 
+To perform an installation you must be able to interact with the serial
+console of the machine.  USB OTG ports such as the one found on the
+BeagleBone will not function as a console.  You need to be able to
+interact with the firmware on the console.  Often this requires a 3.3V
+TTL level adapter connected to pins or a header on the board.
+
 Firmware which provides an EFI interface with a Device Tree Blob (DTB)
 file is required to boot.  In most cases this is provided by images of
 U-Boot 2016.07 or newer on SD/MMC devices or in SPI flash.  If the