[U-Boot] mtdparts: add bad-block skipping

[Ben Gardiner <bengardiner@nanometrics.ca>]

This patch series is based on the idea of Harald Welte <laforge@gnumonks.org>
and the comments of Wolfgang Denk <wd@denx.de> [1]. I started with Harald's
original patch and migrated it to a new mtdparts sub-command and added an
interface to the new functionality via a 'mtdparts add' variant.

I tried to keep it at the level of the mtd subsystem. Whereas the dynparts patch
was limited to NAND flashes, I believe this patch will work on any mtd device
that can report bad blocks.

These new commands can be useful when gang programming NAND chips where the
gang programmer is capable only of skipping bad blocks. One can use a
master image that contains images of each of the partitions padded-out
to their spec'd sizes; when u-boot first comes up 'mtdparts default;
mtdparts spread' (or a seq of 'mtdpart add.e' commands) will produce a partition
table that matches what was put their by the gang-programmer.

It can also be useful when doing in-situ programming with u-boot as the
flash programmer as demonstrated by the openmoko project's use of the
'dynpart' command [2] upon which this patch series was based.

---

NOTE: I'm not sure what to call the new subcommands, I chose 'spread' because
of the way it changes the existing mtdparts variable; however, I am
open to suggestions for a different name. I chose add.e/add.i because of the
behaviour of the write.e/write.i commands; however, I am once again open to
suggestion.

Testing was performed in the u-boot-omap-l1 tree [3]. Here is an example u-boot
console session to demonstrate how the commands work:

---

U-Boot > nand bad

Device 0 bad blocks:
  062c0000
  0a140000
  128a0000
  12e20000
  18bc0000
  1ff80000
  1ffa0000
  1ffc0000
  1ffe0000
U-Boot > mtdparts default
U-Boot > print mtdparts
mtdparts=mtdparts=davinci_nand.1:768k(zero)ro,2m(conf),4m(kernel_a),4m(initrd_a)
,112m(rootfs_a),4m(kernel_b),4m(initrd_b),112m(rootfs_b)
U-Boot >
U-Boot > mtdparts spread
U-Boot > print mtdparts
mtdparts=mtdparts=davinci_nand.1:768k(zero)ro,2m(conf),4m(kernel_a),4m(initrd_a)
,114816k(rootfs_a),4m(kernel_b),4m(initrd_b),114816k(rootfs_b)
U-Boot >
U-Boot > mtdpart del rootfs_b
U-Boot > mtdpart add.e nand0 112m rootfs_b
U-Boot > print mtdparts
mtdparts=mtdparts=davinci_nand.1:768k(zero)ro,2m(conf),4m(kernel_a),4m(initrd_a)
,114816k(rootfs_a),4m(kernel_b),4m(initrd_b),114816k(rootfs_b)

U-Boot > mtdpart del rootfs_b
U-Boot > mtdpart add.i nand0 112m rootfs_b
U-Boot > print mtdparts
mtdparts=mtdparts=davinci_nand.1:768k(zero)ro,2m(conf),4m(kernel_a),4m(initrd_a)
,114816k(rootfs_a),4m(kernel_b),4m(initrd_b),114816k(rootfs_b)
U-Boot >
U-Boot > mtdparts del rootfs_b
U-Boot > mtdparts add nand0 112m rootfs_b
U-Boot > print mtdparts
mtdparts=mtdparts=davinci_nand.1:768k(zero)ro,2m(conf),4m(kernel_a),4m(initrd_a)
,114816k(rootfs_a),4m(kernel_b),4m(initrd_b),112m(rootfs_b)

---

Here are the MAKEALL results:

./MAKEALL arm on master
--------------------- SUMMARY ----------------------------
Boards compiled: 150
Boards with warnings or errors: 47 ( shannon evb4510 lpc2292sodimm modnet50
SMN42 guruplug mv88f6281gtw_ge netstar openrd_base rd6281a sheevaplug suen3
afeb9260 at91cap9adk at91rm9200dk at91rm9200ek at91sam9260ek at91sam9261ek
at91sam9263ek at91sam9g10ek at91sam9g20ek at91sam9m10g45ek at91sam9rlek cmc_pu2
CPUAT91 CPU9260 CPU9G20 csb637 eb_cpux9k2 kb9202 meesc mp2usb m501sk otc570
pm9261 pm9263 SBC35_A9G20 TNY_A9260 TNY_A9G20 actux1 actux2 actux3 actux4
ixdp425 ixdpg425 pdnb3 scpu )
----------------------------------------------------------

./MAKEALL arm with this patch series applied
--------------------- SUMMARY ----------------------------
Boards compiled: 150
Boards with warnings or errors: 47 ( shannon evb4510 lpc2292sodimm modnet50
SMN42 guruplug mv88f6281gtw_ge netstar openrd_base rd6281a sheevaplug suen3
afeb9260 at91cap9adk at91rm9200dk at91rm9200ek at91sam9260ek at91sam9261ek
at91sam9263ek at91sam9g10ek at91sam9g20ek at91sam9m10g45ek at91sam9rlek cmc_pu2
CPUAT91 CPU9260 CPU9G20 csb637 eb_cpux9k2 kb9202 meesc mp2usb m501sk otc570
pm9261 pm9263 SBC35_A9G20 TNY_A9260 TNY_A9G20 actux1 actux2 actux3 actux4
ixdp425 ixdpg425 pdnb3 scpu )
----------------------------------------------------------

[1] http://article.gmane.org/gmane.comp.boot-loaders.u-boot/43549 
[2] http://wiki.openmoko.org/wiki/NAND_bad_blocks
[3] git://arago-project.org/git/people/sekhar/u-boot-omapl1.git