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Subject: Re: UBI: ignore/overwrite old data/PEBs after flashing
From: Artem Bityutskiy <dedekind1@gmail.com>
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On Thu, 2014-10-16 at 07:34 +0200, Rafał Miłecki wrote:
> Hi,
> 
> I need some help with flashing UBI images.
> 
> I work with Broadcom ARM SoCs that use a CFE bootloader. In most cases
> it doesn't provide a way to clear flash content before flashing the
> firmware. It means that if I have 120 MiB of space for the firmware
> and I flash 20 MiB firmware, the rest of flash (100 MiB) won't be
> cleared. My partitioner driver will create 2 MiB partition for kernel
> and 118 MiB partition for UBI.

So what I hear is that the flasher does not provide users the "erase"
operation, but only provides users a "write" operation?

Then the solution would be to pad your image with 0xFFs and write it.
UBI will notice PEBs which do not contain UBI headers and will erase
them in background.

And by the way, this is not related to your problem, but if you are
using a dumb flasher and you wanna use UBIFS, you may need to check the
"space fixup" stuff:

http://www.linux-mtd.infradead.org/faq/ubifs.html#L_free_space_fixup