Changes

We can depict the following approaches to on the field upgrading, depending on the system capabilities and operating environments:

=== U-Boot-based upgrading ===

* Implement software upgrade procedures in u-boot, though possible, is not so easy, due to the limited set of commands provided by the u-boot shell. Moreover, U-Boot usually doesn't support all the available storage devices (for example, on a system with both NOR and NAND flash, it's possible that u-boot supports just the NOR, not allowing to program the NAND flash from the command line).

* Due to the previous considerations, automatic upgrade procedures are hard to implement.

=== Linux-based upgrading ===

* Please note that, in order to erase and write MTD flash partitions, their writability flag must be set in Linux. '''Usually the MTD partition dedicated to u-boot is protected against write in Linux''', so an update of the kernel is required before storing a new u-boot image. Updating U-Boot is not a common operation during the system lifetime, but sometimes it is required to solve some bugs or implement new features.

=== Local upgrading ===