wanting to clarify terminology regarding kernel and device trees

wanting to clarify terminology regarding kernel and device trees

[Robert P. J. Day]

  reading the user manual, section "Booting Linux", about to do a bit
of cleanup there, and i read this:

"NOTE: it may happen that barebox is probed from the devicetree, but
you have want to start a Kernel without passing a devicetree. In this
case call oftree -f to free the internal devicetree before calling
bootm"

  i'm puzzled by the phrase "it may happen that barebox is probed from
the devicetree". i'm sure this is not meant to imply that the device
tree itself does any actual "probing" of barebox. i'm guessing that
what this should really say is something like, "even if barebox has
been built with an internal device tree, you may want to start the
kernel without passing that device tree."  thus, "oftree -f", etc,
etc.

  also, at the risk of being overly pedantic, i would distinguish
between the actions of "probing" and "consulting." i would normally
use the word "probe" in the sense of probing for possible devices, not
knowing if they're there or not. i would use the word "consult" when
one is reading or processing something that is known to be there, such
as the device tree.

  some probably silly questions about device trees coming up shortly
...

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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Re: wanting to clarify terminology regarding kernel and device trees

[Sascha Hauer]

On Fri, Jul 04, 2014 at 09:01:04AM -0400, Robert P. J. Day wrote:
> 
>   reading the user manual, section "Booting Linux", about to do a bit
> of cleanup there, and i read this:
> 
> "NOTE: it may happen that barebox is probed from the devicetree, but
> you have want to start a Kernel without passing a devicetree. In this
> case call oftree -f to free the internal devicetree before calling
> bootm"
> 
>   i'm puzzled by the phrase "it may happen that barebox is probed from
> the devicetree". i'm sure this is not meant to imply that the device
> tree itself does any actual "probing" of barebox. i'm guessing that
> what this should really say is something like, "even if barebox has
> been built with an internal device tree, you may want to start the
> kernel without passing that device tree."  thus, "oftree -f", etc,
> etc.

That is what I wanted to say, yes.

This sometimes happens on ARM when you have a new barebox with internal
devicetree but want to start an older kernel which needs the ATAG list
to start.

> 
>   also, at the risk of being overly pedantic, i would distinguish
> between the actions of "probing" and "consulting." i would normally
> use the word "probe" in the sense of probing for possible devices, not
> knowing if they're there or not.

Indeed we do not have this kind of probing here, so the term might be
misleading.

> i would use the word "consult" when
> one is reading or processing something that is known to be there, such
> as the device tree.

How about devices that are instantiated or populated from the
devicetree? I never heard the word "consult" in this context.

> 
>   some probably silly questions about device trees coming up shortly

Hm, most of the time such silly question turn out to be not silly at all

Sascha

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