IBM Maple platform: Booting yaboot

kksol girmaji7 at
Wed Sep 19 23:52:07 EST 2007

Hi simon,

I am working on PPC970 based platform.This board has PIBS firmware running
on it.My goal is to boot linux from an external SATA hard drive( assuming
PIBS support SATA).I want to use yaboot to load kernel images from SATA hard
drive.I know that PIBS builds OF device tree and provide callbacks for
yaboot.I am not clear with callback registering mechanism.Can anyone explain
what's the exact link between PIBS and yaboot and where to find it?If you
feel PIBS is too specific, co-relate Openfirmware and Yaboot and clear my

Thanks in advance.

jean-francois simon wrote:
> Hi,
> I am using the IBM Maple reference platftorm (dual ppc64 IBM 970FX CPU).
> This board is using a firmware called PIBS that has OpenFirmware 
> extension (builds an OF tree and provides call-backs for yaboot).
> On our final platform we will need to be able to boot from the SCSI bus. 
> So I have written a scsi driver for the PIBS firmware as this wasn't 
> supported.
> I am able to boot the  Yellow dog linux  CDROM  through a SCSI PCI card 
> and run a full install of  YDL linux onto a linux hard drive. This hard 
> drive is intended to be the system drive, and  I need to be able to boot 
> from it.
> My problem is that I am not sure how and where to fetch yaboot from the 
> hard disk.
> Booting yaboot from the yellow dog cdrom was easy: In may scsi driver,  
> I navigate in the ISO9660 file system and I read the file 
> /ppc/bootinfo.txt. This tells me where to find yaboot (in /boot/yaboot). 
> So I load it and all is fine.
> Looking at the hard disk I generated, I can see a /boot/etc/yaboot.conf 
> file:
> ----
> # yaboot.conf generated by anaconda
> boot=/dev/sda
> init-message="Welcome to Yellow Dog Linux! Hit <TAB> for boot options."
> partition=1
> timeout=30
> install=/usr/lib/yaboot/yaboot
> magicboot=/usr/lib/yaboot/ofboot
> delay=10
> enablecdboot
> image=/vmlinux-2.6.10-1.yhpc.6maple
>         label=linux
>         read-only
>         initrd=/initrd-2.6.10-1.yhpc.6maple.img
>         root=/dev/sda2
>         append="console=ttyS0,115200 rhgb quiet"
> ---
> Does it mean the yaboot I need to load and run is /usr/lib/yaboo/yaboot? 
> This is an ELF32 ppc which seems OK.
> My problem is that I need to implement in my firmware scsi driver a 
> layer that undertands linux ext3 partitions,  so that I can reach these 
> files.  I don't mind doing it if this is the right approach but prefer 
> to check first.
> In short I would do the following to boot the scsi hard disk:
> -fetch the MBR (partition table) from the hard disk at offset 0x1be. The 
> table points to the linux ext3 partitions /boot(/dev/sda1)  and / 
> (/dev/sda2)
> -locate the /boot partition and load the /boot/etc/yaboot.conf file.
> -read that file and load the file that is referenced in the install 
> entry (like install=/usr/lib/yaboot/yaboot).
> -yaboot will load  the linix kernel and initrd and I am done.
> Does it seem correct?
> Also I am not sure if I need to use the file "ofboot". In fact I don't 
> understand what is it for?
> Thanks a lot,
> -jf simon
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