[U-Boot] status of patch to store environment to mmc/sd

[Stefano Babic]

Reinhard Meyer wrote:
> Dear Stefano Babic,

Hi Reinhard,

> Just looking at the patch I see that it writes the env to fixed blocks
> on the SD/MMC card. This will work of course. BUT usually (IMHO) such
> cards are used with partitions/filesystems.

Not always. In the specific case reported by Amit, the mx.51 processor
can boot from a SD card, that must not contain partitions at least for
the early sectors, where it is supposed there is the u-boot's code.

Usage of partitions is not forbidden, however. The partitions must only
start after the space required by u-boot and (as supported by the patch
in question) by the environment.

> How do you make sure the
> blocks don't overwrite files or don't get overwritten by files?

Writing a correct partition table: the first partition must start after
u-boot code and environment, used as raw-blocks. There is then no
possibility for files to overwrite the environment or the code.

> One can, of course, prepare the card with a small partition spanning
> the env blocks.

As I said, it is not required to have a partition for the environment,
because this is read only as raw-block. It is only required to skip the
first blocks (or the block set in the config file).

> 
> Should the env not be saved in a file? Which is probably a bit beyond
> possibility to read when not yet relocated...

Reading the environment from a file should be in a separate patch and
made much more general ;-)

It is not related to a specific storage. We could have a filesystem even
on other storages (SPI-Flash, NAND, HD...) and "reading from file"
should IMHO hide the underlying storage media.

Best regards,
Stefano

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