Android: modify partition layouts

Storage is never enough!
Fortunately, we can pass partition layouts via kernel command line without kernel modification.
lbcoder, Thanks for post this! Custom partition layouts, ZERO brick risk!

My Nexus One default partition layouts:

# cat /proc/mtd

dev:    size   erasesize  name          size
mtd0: 000e0000 00020000 "misc"          896K

mtd1: 00400000 00020000 "recovery"      4M

mtd2: 00380000 00020000 "boot"          3M

mtd3: 09100000 00020000 "system"        145M

mtd4: 05f00000 00020000 "cache"         95M

mtd5: 0c440000 00020000 "userdata"      196M

# msm_nand MTD info during kernel booting
[   13.353302] msm_nand: DEV_CMD1: f00f3000

[   13.357299] msm_nand: NAND_EBI2_ECC_BUF_CFG: 1ff
[   13.361724] Creating 6 MTD partitions on "msm_nand":
[   13.366790] 0x000003ee0000-0x000003fc0000 : "misc"
[   13.373260] 0x000004240000-0x000004640000 : "recovery"
[   13.381561] 0x000004640000-0x0000049c0000 : "boot"
[   13.386108] 0x0000049c0000-0x00000dac0000 : "system"
[   13.538635] 0x00000dac0000-0x0000139c0000 : "cache"
[   13.637023] 0x0000139c0000-0x00001fe00000 : "userdata"
 

cache partition is too large to me.

I would like to change partition layouts to

dev:    size   erasesize  name          size
mtd0: 000e0000 00020000 "misc"          896K

mtd1: 00400000 00020000 "recovery"      4M

mtd2: 00380000 00020000 "boot"          3M

mtd3: 09100000 00020000 "system"        145M

mtd4: 02800000 00020000 "cache"         95M->40M
mtd5: 0FB00000 00020000 "userdata"      196M->251M

userdata partition up to 251M!

So, I need add kernel command line like below

mtdparts=msm_nand:896k@0x3ee0000(misc),4M@0x4240000(recovery),3M@0x4640000(boot),145M@0x49c0000(system),40M@0xdac0000(cache),251M@0x102C0000(userdata)

But how?

I do it manually. We need to modify both recovery and boot images.

1. Boot to recovery mode
2. Extract recovery image from recovery partition and use hex editor to add kernel command line into recovery image
3. Flash back modified recovery image then boot to recovery again
4. Check MTD information, we are done.
   [    9.726074] msm_nand: DEV_CMD1: f00f3000
   [    9.726257] msm_nand: NAND_EBI2_ECC_BUF_CFG: 1ff
   [    9.726440] 6 cmdlinepart partitions found on MTD device msm_nand
   [    9.726684] Creating 6 MTD partitions on "msm_nand":
   [    9.726837] 0x000003ee0000-0x000003fc0000 : "misc"
   [    9.728668] 0x000004240000-0x000004640000 : "recovery"
   [    9.733581] 0x000004640000-0x000004940000 : "boot"
   [    9.737548] 0x0000049c0000-0x00000dac0000 : "system"
   [    9.893493] 0x00000dac0000-0x0000102c0000 : "cache"
   [    9.937652] 0x0000102c0000-0x00001fdc0000 : "userdata" 
5. Flash zip from SD (I use CM7.2)
6. Extract boot image from boot partition and use hex editor to add kernel command line into boot image
7. Flash back modified boot image then reboot
8. Boot to CM, then check MTD information.