[U-Boot-Users] using a flat device tree to drive u-boot config

Wolfgang Grandegger
2008-07-29T08:41:32Z

Andr? Schwarz wrote:
> Ben Warren schrieb:
>> On Mon, Jul 28, 2008 at 10:43 AM, Scott Wood <scottwood@freescale.com> wrote:
>>> Ben Warren wrote:
>>>> On Mon, Jul 28, 2008 at 10:32 AM, Scott Wood <scottwood@freescale.com>
>>>> wrote:
>>>>> I find a device tree much easier to figure out than a tangled mess of
>>>>> header
>>>>> files, #defines, and #ifdefs...
>>>> In many ways, yes. But are you an average Joe or a Linux kernel
>>>> propellerhead?
>>> Is u-boot work normally done by average Joes, and does the average Joe
>>> really find the preprocessor mess more intuitive than a "propellerhead"?
>>>
>> You know what I mean. Some people like yourself do this for a living,
>> and are involved day-to-day in its specification. Of course it's
>> intuitive to you. For most people, getting U-boot going is one stage
>> in the development process of software for an embedded device. They
>> work on it for a few weeks or months, then on something completely
>> different. A few months or years later, they come back to it.
>
> You're absolutely right - just have a look at the vast lists of
> maintainers/contributors ... they are "average Joes" like myself.
> Realizing 2-3 projects each year should be possible without having to
> re-learn from scratch.
>
>>> While we're at it, let's re-write u-boot in Visual Basic. :-)
>> Uh, yeah. I like the idea of a central repo for hardware info, and
>> the device tree concept is good. My point is that the syntax, while
>> concise and exact, can be intimidating. Just look at the amount of
>> traffic on the mailing lists of people that don't understand what all
>> the fields mean when specifying IRQs etc. Anything we can do to make
>> it less so for noobies is a good thing for everybody.
>>
>
> Please keep in mind that WDenk is always watching if code is slowing
> things down or increasing size significantly. Improving things is very
> good - but not at the cost of size and/or speed. Configuring a board
> using a dtb usually needs far more code being present than needed.
> After all it's a bootloader and not another pseudo OS.
>
> But don't get me wrong ! The device tree is a very nice and usefuly
> thing ... for an OS.

There are customer request for a dynamically configurable U-Boot and the
FDT is the right tool to provide the functionality. It has its price but
U-Boot using a FDT blob for booting would also save some fixup code
(required to boot Linux) and furthermore it would resolves some
dependencies between hardcoded U-Boot and FDT defined addresses and ranges.

Wolfgang.