Block based OTA update needs mtdblock

[Miquel Raynal]

Hello,

On 20/11/2024 at 12:52:57 +0530, Pintu Agarwal <pintu.ping at gmail.com> wrote:

> Hi,
>
> On Mon, 4 Nov 2024 at 21:31, Pintu Agarwal <pintu.ping at gmail.com> wrote:
>>
>> Hi All,
>>
>> For one of our automotive products we have the following configuration:
>> QC chipset, arm64, Kernel-5.15, NAND Flash 1GB, A/B system, UBI
>> volumes (squashfs, ubifs), DM-verity for rootfs (squashfs), simple
>> busybox platform.
>>
>> For OTA updates we have a strong dependency with MTD_BLOCK.
>>
>> Till now, we were using ubiblock for mounting squashfs volumes and
>> completely got rid of mtd_block by configuring it as a loadable
>> module.
>> But, we also need to support OTA updates (Full, Incremental) on A/B
>> volumes using the same Android OTA framework.
>> https://source.android.com/docs/core/ota/nonab/block
>>
>> OTA update will be applied to the B (inactive) partition.
>> OTA updates prefer block based update over file based especially for
>> dm-verity enabled devices.
>>
>> Now, the problem is, on MTD we only have 2 options for block based
>> updates; ubi_block or mtd_block.
>> We cannot use ubiblock for OTA updates as it is read only.
>> For full update volume, we can use "ubiupdatevol" interface to
>> completely replace the volume content, but for partial or incremental
>> update we need to update only specific blocks and not entire
>> partitions.
>> Thus, we have to use the MTD_BLOCK (/dev/mtdblock) interface to
>> support block based OTA updates on UBI volumes.
>> Thus, during ota updates (only) we need to install the mtdblock
>> module, perform the update and then uninstall the module.
>>
>> That means, we cannot completely get rid of MTD_BLOCK from our product
>> especially for OTA use cases.
>>
>> Is this the only way, or do we have any other option to support OTA
>> updates over UBI volumes ?
>>
> Restarting this thread again...
> Any further comment on this ?
>
> Did anybody used block based OTA update NAND A/B system without using
> mtd_block ?

Not on my side, it is actually a good question. Richard, any ideas?

> Since ubiblock is read-only, it seems there is no other way to perform
> OTA update, if mtd_block is disabled.
> Or, we need to make ubiblock also as read/write.

Doesn't sound possible/a good idea.

I'm sorry for this unhelpful answer :-)

Miquèl