[U-Boot] Multiple device support - none at all?

[ksi at koi8.net]

On Thu, 12 Mar 2009, Detlev Zundel wrote:

> Hi ksi (was it Sergei?),
> 
> >> The fundamental concept of u-boot isn't to handle all your devices, it is to
> >> boot linux (or other OS) and use the OS to handle the multiple devices.
> >
> > The same is true for a PC BIOS, but it DOES handle all of my devices. And it
> > allows me to choose which device to boot from. And it is extendable so I can
> > add a PCI card with e.g. RAID controller and boot off of that RAID. And it
> > is not handling of all devices, it is _BASIC_ functionality...
> 
> Actually I don't know what you're talking about in the PC BIOS area
> here.  Usually the computers I own cannot boot from the devices that are
> bought somewhat after the motherboard.  But maybe you have different
> instances of computers...

First of all, there are several bootable devices on a motherboard itself.
These days almost every motherboard has PATA and some kind of SATA RAID
controller onboard. Then, it can usually boot off of USB while having USB
keyboard/mouse. As for add-on devices, it usually CAN boot off of those
devices. They have their own BIOS for that that gets attached to the
motherboard's one when it initializes and those devices are added to the
boot table.

> > I don't mind reconfiguring and rebuilding the thing for my parcticular
> > configuration instead of just changing some settings in interactive setup
> > utility, but the current implementation won't allow even that...
> 
> Actually we are thinking about "going generic" here also for a while
> already.  Look for example at the BOF session notes of OLS 2007[1]
> "Device Tree Run Time Configuration".
> 
> We are all aware that a "proper" device model will be needed at a
> certain stage, only nobody started into that direction yet.
> 
> As Jerry pointed out - booting embedded hardware used to be a comparably
> simple operation ;)

There is a whole world beyond that keyhole... Embedded devices yes, but
there are other boards that don't fall in that category. My current MPC8548
based board is not an embedded one, it is full-blown mATX motherboard with
several USB controllers, PATA, SATA, Video Capture, VGA/LCD controller,
PCI-X/PCI/PCIe connectors etc.

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