Re: [PATCH] wic: allow creation of partitions not in table

[Maciej Borzecki <maciej.borzecki@open-rnd.pl>]

On 02/05 11:27, Alexandre Belloni wrote:
> Hi,
>
> On 05/02/2015 at 10:02:26 +0100, Maciej Borzecki wrote :
> > On 02/05 00:03, Alexandre Belloni wrote:
> > > For some architectures it is necessary to reserve space on disk without
> > > it being present in the partition table.
> > >
> > > For example, u-boot on i.mx is placed at an offset of 1kB on the sdcard.
> > > While it would be possible to create a partition at that offset and
> > > place u-boot there, it would then be necessary to update the default
> > > u-boot environment to use partition 2 on the mmc instead of partition
> > > 1.
> >
> > I'm wondering if reusing parition here is the right choice. How about
> > making this a separate command, since the operation of putting some
> > binary data at a particular location within the image sounds like
> > something very specific to wic.
> >
> > Could name it 'raw-copy', with options --source and --offset. The
> > command would be applied after image assembly is complete. Offset could
> > be expressed in bytes by default (plus k/M/G suffix). Source could
> > either be a 'bootloader', that implies a default bootloader for this
> > target, or a name of a file from $DEPLOY_DIR_IMAGE.
> >
> > Assuming IMAGE_BOOTLOADER='u-boot.img' is set somewhere, the kickstart
> > could look like:
> >
> > part / --source rootfs --ondisk mmcblk --fstype=ext4 --label root --align 4 --start 1M
> > raw-copy --source bootloader --offset 1kB
> >
> >
> > If at some point we extend the bootloader command to include the name of
> > bootloader file:
> >
> > part / --source rootfs --ondisk mmcblk --fstype=ext4 --label root --align 4 --start 1M
> > bootloader --name u-boot.img
> > raw-copy --source bootloader --offset 1kB
> >
> > What do you think?
> >
>
> I though about that, I actually created a rawcopy plugin to dump file
> into partitions.
>
> The main issue with what you suggest is that you lose the whole
> automatic offset calculations. What if the bootloader is larger than 1M
> in your example? It will overwrite / You also lose the alignment
> calculations unless you add them back in the new class.
>
> Another issue is that you may want to copy multiple files at different
> offsets. For example for am335x:
> SPL at 128k, backup SPL at 256k, u-boot at 384k in a partition, u-boot
> environment in a partition, rootfs.

Booting from eMMC?

>
> This would give something like:
> part SPL --source rawcopy --sourceparams="file=MLO" --ondisk mmcblk --no-table --align 128
> part SPL.backup --source rawcopy --sourceparams="file=MLO" --ondisk mmcblk --no-table --align 128
> part uboot --source rawcopy --sourceparams="file=u-boot.img" --ondisk mmcblk --align 128
> part uboot.env --source rawcopy --sourceparams="file=u-boot.env" --ondisk mmcblk --align 128
> part / --source rootfs --ondisk mmcblk --fstype=ext4 --label root --align 4
>

It makes sense now, rawcopy plugin is what I have been missing. I'd be
careful with --align though. It would be much more readable to have an
explicit --start or --offset option, but that has been sitting in my
TODO list for quite some time now.

Other than that the patch looks good to me.

--
Maciej Borzęcki
Senior Software Developer at Open-RnD Sp. z o.o., Poland
www.open-rnd.pl
mobile: +48 889 117 365, fax: +48 42 657 9079


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