Block based OTA update needs mtdblock

[Zhihao Cheng]

在 2024/11/5 0:01, Pintu Agarwal 写道:
> 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.

Hi Pintu, how do you export the mtdblock device over on an UBI volume? 
By the gluebi?
> 
> 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 ?
> 
> 
> Thank you,
> Regards,
> Pintu
> .
>