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    SubjectRe: MTD: How to get actual image size from MTD partition
    ----- Ursprüngliche Mail -----
    > Von: "Pintu Agarwal" <pintu.ping@gmail.com>
    > Okay thank you.
    > We have tried dm-verity with squashfs (for our rootfs) but we are
    > facing some mounting issues.
    > [...]
    > [ 4.697757] device-mapper: init: adding target '0 96160 verity 1
    > /dev/mtdblock34 /dev/mtdblock39 4096 4096 12020 8 sha256
    > d7b8a7d0c01b9aec888930841313a81603a50a2a7be44631c4c813197a50d681
    > aee087a5be3b982978c923f566a94613496b417f2af592639bc80d141e34dfe7'
    > [ 4.704771] device-mapper: verity: sha256 using implementation
    > "sha256-generic"
    > [...]
    > [ 4.727366] device-mapper: init: dm-0 is ready
    > [ 4.912558] VFS: Cannot open root device "dm-0" or
    > unknown-block(253,0): error -5
    >
    > The same works with ext4 emulation.
    > So, not sure if there are any changes missing w.r.t. squashfs on 4.14 kernel ?

    I don't know.

    > Anyways, I will create a separate thread for dm-verity issue and keep
    > this thread still open for UBI image size issue.
    > We may use dm-verify for rootfs during booting, but still we need to
    > perform integrity check for other nand partitions and UBI volumes.
    >
    > So, instead of calculating the checksum for the entire partition, is
    > it possible to perform checksum only based on the image size ?
    > Right now, we are still exploring what are the best possible
    > mechanisms available for this.

    I still don't fully understand what you are trying to achieve.
    Is it about cryptographic integrity of your storage or detecting
    errors after the flashing process?

    But let me advertise ubiblock a second time. If you place your squashfs on
    a UBI static volume, UBI knows the exact length and you can checksum it
    more easily.

    Thanks,
    //richard

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