linux-kernel - Re: Block based OTA update needs mtdblock

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Message-ID: <CAOuPNLhhWzoBQH85zEd95LbONtrknq+b7tfcze50VPa9bEnXzw@mail.gmail.com>
Date: Wed, 20 Nov 2024 12:52:57 +0530
From: Pintu Agarwal <pintu.ping@...il.com>
To: Miquel Raynal <miquel.raynal@...tlin.com>, Richard Weinberger <richard@....at>, 
	Vignesh Raghavendra <vigneshr@...com>, linux-mtd <linux-mtd@...ts.infradead.org>, chengzhihao1@...wei.com, 
	open list <linux-kernel@...r.kernel.org>, kernelnewbies@...linux.org
Subject: Re: Block based OTA update needs mtdblock

Hi,

On Mon, 4 Nov 2024 at 21:31, Pintu Agarwal <pintu.ping@...il.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 ?
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.


Thanks,
Pintu