[PATCH] Makefile: remove block from conv=block,sync in SPL alignment dd

[Tom Rini]

On Fri, May 01, 2026 at 09:38:50AM -0500, Brad Klingerman wrote:

> The line that produces $(SPL_BIN)-align.bin invokes dd with
> conv=block,sync but no cbs= operand. The result of dd conv=block
> without cbs= is unspecified. GNU coreutils outputs anyway, but
> uutils (default in Ubuntu 26.04 LTS) errors out for files with
> newlines, including SPL binaries, producing:
> 
>     dd: conv=block or conv=ubnblock specified without cbs=N
> 
> Either the block operand must be removed, or cbs=N must be added.
> conv=block is for converting newline-terminated variable-length
> records to fixed-length space-padded ones, which is meaningless
> for a binary SPL image. The intent of the rule is 4-byte
> alignment, which conv=sync alone provides by padding the final
> block to bs= bytes with NULs.
> 
> During build, u-boot-spl-align.bin errors silently due to '@'.
> 
> Reproduced with uutils dd 0.8.0:
> 
>     $ dd if=/dev/urandom of=/tmp/in bs=1 count=10000
>     $ dd if=/tmp/in of=/tmp/out conv=block,sync bs=4
>     dd: conv=block or conv=unblock specified without cbs=N
>     $ dd if=/tmp/in of=/tmp/out conv=sync bs=4
>     [succeeds]
> 
> Output is byte-identical to GNU dd's output for binary input.
> 
> Signed-off-by: Brad Klingerman <bdklingerman at gmail.com>

Reviewed-by: Tom Rini <trini at konsulko.com>

-- 
Tom
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