mtdpartikr - MTD partitioning in kernel runtime

mtdpartikr is a component in the nfiop project, which is intended for providing a capability of partitioning an MTD device in kernel runtime.

mtdpartikr is also a kernel module which registers new character devices for master MTD devices, to allow userspace to create MTD partitions in kernel runtime, without rebooting, after the boot process is completed.

It accomplishes re-partitioning of MTDs by spawning its own proxy MTDs which are backed by existing MTDs, and with tight control over the lifetime model of the proxy MTDs, the kernel module is able to respawn the proxy MTDs with new partition tables when such operation is needed.

Together with mtdpartd, it serves as a vital component in the nfiop ecosystem, where otherwise it would be much harder to handle different parts of a flash chip separately.

mtdpartikr is designed specifically for flash devices and can filter based on the MTD type - for now, either a NAND or NOR flash device.

On the word "partikr"

mtdpartikr is pronounced as "partiker" (em-tee-dee-par-tee-ker).

"partiker" is not a word in English, but its sound might be catchy and the resemblence to the word of "party" could have a somewhat joyful meaning to the name as well.

Prepare for compiling

If not clean, clean the build directory

./build.sh clean

Cross compile (with buildroot)

Simply run (with adjustments to your buildroot path):

./build.sh --buildroot ../buildroot/

Why do you write this module?

Sadly, there's no real easy way to define multiple MTD partitions after the boot process is done.

Traditional embedded platforms have hardcoded offsets for MTD partitions or might include them in a device tree blob, for "convenience".

There's the mtdpart utility in the mtd-utils package that might serve some of the offered functionality of this module.

This kernel module, together with additional userspace code, are meant to allow dynamic partitioning in kernel runtime, after the boot process is completed.

It offers a mechanism to invoke a controlled procedure of defining new MTD partitions on an MTD device, with the ability of controlling flags like MTD_WRITABLE and MTD_POWERUP_LOCK which to the best of my knowledge are not available on the mtdpart utility.

How do I use this module?

This module is not supposed to be installed alone on an embedded machine or a platform that has an MTD device (or even multiple).

It should be paired with the rest of the nfiop ecosystem, serving as a complementary component for ufedm for slicing a backing MTD device to logical chunks for differential processing.

See instructions about testing to learn more about actual usage.

Limitations

• mtdpartikr doesn't intend to support unaligned offsets. You must read the MTD erasesize (also available from our ioctl interface) and calculate an aligned offset.

  The reason for this is to ensure erase semantics are always valid on all platforms and drivers.

• mtdpartikr doesn't provide a way to batch-remove multiple MTD partitions nor "reset" an MTD device back to a state of no partitions.

  The kernel doesn't support such mechanism easily, so I didn't bother to build something complicated when the solution is to either reboot or, (unsafely due a possible userspace race condition) delete each partition on your risk.