maemo.org - Talk - MTD devices

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- Nokia N900 (https://talk.maemo.org/forumdisplay.php?f=44)

- - MTD devices (https://talk.maemo.org/showthread.php?t=62468)

Hi to all,

I would like to understand somethings better of the mtd devices.

Code:

# cat /proc/mtd

dev:    size   erasesize  name

mtd0: 00020000 00020000 "bootloader"

mtd1: 00060000 00020000 "config"

mtd2: 00040000 00020000 "log"

mtd3: 00200000 00020000 "kernel"

mtd4: 00200000 00020000 "initfs"

mtd5: 0fb40000 00020000 "rootfs"

mtd0 the bootloader can I flash it? I read the thread. Is it possible to flash an empty internal flash without solder? I think no, so is better don't touch this part of internal flash.
mtd1 which config?
mtd2 which log?
mtd3 ok the kernel
mtd4 initfs????
mtd5 the root filesystem ubifs. Can I mount the image on PC with linux? I tried to mount with a kernel 2.6.27.48 but I got the error -22.

Thank you

kernel OOPSes end up in mtd2

mtd2 is not cleared even if full reflash is done, have you noticed?
I've done both flashing from Linux rootfs and eMMC and then also with Nokia PC-suite, but mtd2 stays the same over the firmware updates.

Kinda interesting OOPSes there.

Code:

strings /dev/mtd2ro | less

If mtd2 log shows you have used maemo Extras-devel and -test packages, does it destroy your warranty? Kernel-power usage shows there for most people I am sure.

mtd0 - if you re-flash it and do something wrong you can trash your N900 or try to exchange. W/out special means it could be impossible to revive N900. Then you type 'u' during switch ON while on USB it is actually bootloader which responds to this. So - refrain to change mtd0.

mtd1 - it has all radio chips and other Nokia configuration... in encoded form, I think. And I think it keeps lock and other stuff like this.

mtd2 - crash log. Kernel writes crash messages to it, sequentially. You can copy it via "cat /dev/mtd2 >somefile" and send it to bugs.maemo.org or directly to Nokia for analysis.

mtd3 - current kernel. If you corrupt it you may still able to restore N900 via reflashing kernel and I think noloboot bootloader can handle this while you press 'u' during switching ON on USB cable connected.

mtd4 - it is a place for initfs which MAY be used during boot. It seems it is not used today. It is kept for compatibility or for future. Today you can keep your porn here.

mtd5 - root FS with UBIFS file system type. You can't mount it without proper kernel drivers. It includes UBIFS and some low-level drivers too. I have no idea - is it possible to ignore low-level drivers to mount an image, because UBIFS module uses 'erase' or 'flash' feature of low-level driver. Just read/write is not enough.

EDIT: look into this - https://wiki.maemo.org/Updating_the_.../Cold_Flashing - it seems it is still possible to restore nolo bootloader in mtd0 after corruption by cold flush. I didn't verify that, of course.