[U-Boot] [PATCH v2 2/2] cmd: Add 'bcb' command to read/modify/write BCB fields

[Simon Glass]

Hi Eugeniu,

On Fri, 17 May 2019 at 08:46, Eugeniu Rosca <erosca at de.adit-jv.com> wrote:
>
> 'Bootloader Control Block' (BCB) is a well established term/acronym in
> the Android namespace which refers to a location in a dedicated raw
> (i.e. FS-unaware) flash (e.g. eMMC) partition, usually called "misc",
> which is used as media for exchanging messages between Android userspace
> (particularly recovery [1]) and an Android-capable bootloader.
>
> On higher level, this allows implementing a subset of Android Bootloader
> Requirements [2], amongst which is the Android-specific bootloader
> flow [3]. Regardless how the latter is implemented in U-Boot ([3] being
> the most memorable example), reading/writing/dumping the BCB fields in
> the development process from inside the U-Boot is a convenient feature.
> Hence, make it available to the users.
>
> Some usage examples of the new command recorded on R-Car H3ULCB-KF
> ('>>>' is an overlay on top of the original console output):
>
> => bcb
> bcb - Load/set/clear/test/dump/store Android BCB fields
>
> Usage:
> bcb load  <dev> <part>       - load  BCB from mmc <dev>:<part>
> bcb set   <field> <val>      - set   BCB <field> to <val>
> bcb clear [<field>]          - clear BCB <field> or all fields
> bcb test  <field> <op> <val> - test  BCB <field> against <val>
> bcb dump  <field>            - dump  BCB <field>
> bcb store                    - store BCB back to mmc
>
> Legend:
> <dev>   - MMC device index containing the BCB partition
> <part>  - MMC partition index or name containing the BCB
> <field> - one of {command,status,recovery,stage,reserved}
> <op>    - the binary operator used in 'bcb test':
>           '=' returns true if <val> matches the string stored in <field>
>           '~' returns true if <val> matches a subset of <field>'s string
> <val>   - string/text provided as input to bcb {set,test}
>           NOTE: any ':' character in <val> will be replaced by line feed
>           during 'bcb set' and used as separator by upper layers
>
> => bcb dump command
> Error: BCB not loaded!
>  >>> Users must specify mmc device and partition before any other call
>
> => bcb load 1 misc
> => bcb load 1 1
>  >>> The two calls are equivalent (assuming "misc" has index 1)
>
> => bcb dump command
> 00000000: 62 6f 6f 74 6f 6e 63 65 2d 73 68 65 6c 6c 00 72    bootonce-shell.r
> 00000010: 79 00 72 00 00 00 00 00 00 00 00 00 00 00 00 00    y.r.............
>  >>> The output is in binary/string format for convenience
>  >>> The output size matches the size of inspected BCB field
>  >>> (32 bytes in case of 'command')
>
> => bcb test command = bootonce-shell && echo true
> true
> => bcb test command = bootonce-shell- && echo true
> => bcb test command = bootonce-shel && echo true
>  >>> The '=' operator returns 'true' on perfect match
>
> => bcb test command ~ bootonce-shel && echo true
> true
> => bcb test command ~ bootonce-shell && echo true
> true
>  >>> The '~' operator returns 'true' on substring match
>
> => bcb set command recovery
> => bcb dump command
> 00000000: 72 65 63 6f 76 65 72 79 00 73 68 65 6c 6c 00 72    recovery.shell.r
> 00000010: 79 00 72 00 00 00 00 00 00 00 00 00 00 00 00 00    y.r.............
>  >>> The new value is NULL-terminated and stored in the BCB field
>
> => bcb set recovery "msg1:msg2:msg3"
> => bcb dump recovery
> 00000040: 6d 73 67 31 0a 6d 73 67 32 0a 6d 73 67 33 00 00    msg1.msg2.msg3..
> 00000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
> 00000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
>  >>> --- snip ---
>  >>> Every ':' is replaced by line-feed '\n' (0xA). The latter is used
>  >>> as separator between individual commands by Android userspace
>
> => bcb store
>  >>> Flush/store the BCB structure to MMC
>
> [1] https://android.googlesource.com/platform/bootable/recovery
> [2] https://source.android.com/devices/bootloader
> [3] https://patchwork.ozlabs.org/patch/746835/
>     ("[U-Boot,5/6] Initial support for the Android Bootloader flow")
>
> Signed-off-by: Eugeniu Rosca <erosca at de.adit-jv.com>
> ---
> v2:
>  - [Heinrich Schuchardt] Implement sub-commands via U_BOOT_CMD_MKENT.
>  - Polished the code. Ensured no warnings returned by sparse, smatch,
>    `cppcheck --force --enable=all --inconclusive`, make W=1.
>  - Tested on R-Car-H3-ES20 ULCB-KF.
>
> v1:
>  - https://patchwork.ozlabs.org/patch/1080395/
> ---
>  cmd/Kconfig  |  17 +++
>  cmd/Makefile |   1 +
>  cmd/bcb.c    | 330 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 348 insertions(+)
>  create mode 100644 cmd/bcb.c

Where is this documented? Perhaps it should go in README.avb2?

Should it default to enabled if avb is used?

Regards,
Simon