Re: [PATCH 0/8] blk: blkmap: Composable virtual block devices

[Simon Glass <sjg@chromium.org>]

Hi Tobias,

On Wed, 1 Feb 2023 at 11:10, Tobias Waldekranz <tobias@waldekranz.com> wrote:
>
> Block maps are a way of looking at various sources of data through the
> lens of a regular block device. It lets you treat devices that are not
> block devices, like RAM, as if they were. It also lets you export a
> slice of an existing block device, which does not have to correspond to
> a partition boundary, as a new block device.
>
> This is primarily useful because U-Boot's filesystem drivers only
> operate on block devices, so a block map lets you access filesystems
> wherever they might be located.
>
> The implementation is loosely modeled on Linux's "Device Mapper"
> subsystem, see the kernel documentation [1] for more information.
>
> The primary use-cases are to access filesystem images stored in RAM, and
> within FIT images stored on disk. See doc/usage/blkmap.rst for more
> details.
>
> The architecture is pluggable, so adding other types of mappings should
> be quite easy.
>
> [1]: https://docs.kernel.org/admin-guide/device-mapper/index.html
>
> Tobias Waldekranz (8):
>   image: Fix script execution from FIT images with external data
>   cmd: blk: Allow generic read/write operations to work in sandbox
>   blk: blkmap: Add basic infrastructure
>   blk: blkmap: Add memory mapping support
>   blk: blkmap: Add linear device mapping support
>   cmd: blkmap: Add blkmap command
>   test: blkmap: Add test suite
>   doc: blkmap: Add introduction and examples
>
>  MAINTAINERS                      |   9 +
>  boot/image-board.c               |   3 +-
>  cmd/Kconfig                      |  19 ++
>  cmd/Makefile                     |   1 +
>  cmd/blk_common.c                 |  15 +-
>  cmd/blkmap.c                     | 181 +++++++++++++
>  configs/sandbox_defconfig        |   1 +
>  disk/part.c                      |   1 +
>  doc/usage/blkmap.rst             | 109 ++++++++
>  doc/usage/index.rst              |   1 +
>  drivers/block/Kconfig            |  18 ++
>  drivers/block/Makefile           |   1 +
>  drivers/block/blk-uclass.c       |   1 +
>  drivers/block/blkmap.c           | 452 +++++++++++++++++++++++++++++++
>  include/blkmap.h                 |  21 ++
>  include/dm/uclass-id.h           |   1 +
>  include/efi_loader.h             |   4 +
>  lib/efi_loader/efi_device_path.c |  30 ++
>  test/py/tests/test_blkmap.py     | 164 +++++++++++
>  19 files changed, 1027 insertions(+), 5 deletions(-)
>  create mode 100644 cmd/blkmap.c
>  create mode 100644 doc/usage/blkmap.rst
>  create mode 100644 drivers/block/blkmap.c
>  create mode 100644 include/blkmap.h
>  create mode 100644 test/py/tests/test_blkmap.py
>
> --
> 2.34.1
>

Overall this looks good to me. I'll make suggestions on the individual patches.

The main thing to note is that device numbers are an internal thing
that I'd like to move away from, so labels are better.

Regards,
Simon