[U-Boot] precedence of specifying mtdparts using DTB versus "mtdparts="?

[Robert P. J. Day]

  i'm sure i'm just being an idiot here (pause for hysterical
laughter), but what is the precedence for overriding the partition
layout of flash using one of:

1) "mtdparts=" added to the kernel command line, or
2) using "fdt" command to hack DTB to change partition layout

  the scenario is a perfectly decent DTB defining the breakdown of 2M
of NOR flash ... that is unfortunately being used on a system with 4M
of flash, where the first 2M should be ignored and the second 2M is
what should be used. so all i want to do is tweak the flash definition
to say that, yes, i have 4M of NOR flash, but let's add a 2M "junk"
partition at the front so i can skip that and get to the normal stuff.

  (i realize that will shift all /dev/mtd* names by one, no problem,
i can handle that.)

  first question -- if i define flash layout both in the DTB and on
the kernel command line, which one takes precedence?

  second question -- if the DTB layout takes precedence (i'm guessing
it does), is it sufficient to use the "fdt" command to remove all of
the partition definitions so that the kernel command line will be
consulted? (i don't mean remove the entire flash node from the DTB,
just the set of internal partition definitions.)

  final question -- i was trying to use mtdparts= on the command
line, and it seemed like i was supplying the wrong value for <mtd-id>
in:

mtdparts=<mtddef>[;<mtddef]
<mtddef>  := <mtd-id>:<partdef>[,<partdef>]
<partdef> := <size>[@offset][<name>][ro]
<mtd-id>  := unique id used in mapping driver/device (number of flash bank)
<size>    := standard linux memsize OR "-" to denote all remaining space
<name>    := '(' NAME ')'

upon further reading, it seems that i can figure out the proper value
for <mtd-id> based on this page:

  http://lists.denx.de/pipermail/u-boot/2011-April/089620.html

so i can just run "mtdparts" and i should get the proper name to use
for mtd-id, is that correct?

rday

-- 

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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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