Date: Sat, 9 Feb 2013 23:03:38 -0800 From: Tim Kientzle <tim@kientzle.com> To: Brett Wynkoop <wynkoop@wynn.com> Cc: freebsd-arm@freebsd.org Subject: Re: building RaspPi Images Message-ID: <58DCA6BE-8C06-4F69-81A2-A3582FBB5B12@kientzle.com> In-Reply-To: <20130210012052.4d7e1a46@ivory.local> References: <5116CB50.9080303@ceetonetechnology.com> <7757848F-45C6-4DEF-A4A2-5F900EB10A06@kientzle.com> <20130210012052.4d7e1a46@ivory.local>
next in thread | previous in thread | raw e-mail | index | archive | help
On Feb 9, 2013, at 10:20 PM, Brett Wynkoop wrote:
>
> I was thinking that we should be able to generate a generic image that
> will boot on both the Pi and the Bone. Maybe a config file that
> includes the needed drivers for both boards.
I've thought about this and believe it is pretty routine,
though I've not had time to actually try implementing it.
This specific combination is simplified by the fact
that the boot bits are so different, so you can just
put them all on the same SD card image.
There are a few pieces you'll need to work through:
1. An MSDOS partition with all the boot bits from both systems
2. A kernel with all of the drivers for both systems
3. ubldr will need to identify the board somehow
4. ubldr will need to obtain the correct FDT
Except for #3, this should all be entirely routine.
For #4, the trick is to not compile any DTB into the
kernel. Instead, the DTB is given to the kernel by
the boot bits:
* For RPi, this already happens: the first-stage boot
loads a DTB, ubldr uses "fdt addr" to access that DTB
in a known location and then passes it to the kernel.
* For Beaglebone, you can use loader.rc commands to load
the proper DTB from the UFS partition. I'm using the following
on my BeagleBone right now:
/boot/beaglebone.dtb
/boot/loader.rc contains
load /boot/kernel/kernel
load -t dtb /boot/beaglebone.dtb
autoboot
This should be an afternoon's work for someone who already
has a good understanding of FreeBSD boot processes.
Tim
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?58DCA6BE-8C06-4F69-81A2-A3582FBB5B12>