[Buildroot] [PATCH 2/4] support/testing/infra: add img_round_power2() function

[Yann E. MORIN]

Thomas, All,

On 2021-06-21 22:25 +0200, Thomas Petazzoni spake thusly:
> Since Qemu 5.1, SD card images must have a size that are a power of
> two. While some filesystem (such as ext2/3/4) allow to specify the
> expected size of the filesystem, others such as SquashFS do not have
> this capability.
> 
> We were already extending the size of such images to the next 1 MB
> boundary using "truncate -s %1M", but that is no longer sufficient. So
> instead, we introduce a helper function that extends the size of an
> image to the next power of two.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
> ---
>  support/testing/infra/__init__.py | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/support/testing/infra/__init__.py b/support/testing/infra/__init__.py
> index 6522a265f3..c540fd1940 100644
> --- a/support/testing/infra/__init__.py
> +++ b/support/testing/infra/__init__.py
> @@ -112,3 +112,14 @@ def get_elf_prog_interpreter(builddir, prefix, fpath):
>              continue
>          return m.group(1)
>      return None
> +
> +
> +def img_round_power2(img):
> +    """
> +    Rounds up the size of an image file to the next power of 2
> +    """
> +    sz = os.stat(img).st_size
> +    pow2 = 1
> +    while pow2 < sz:
> +        pow2 = pow2 << 1
> +    subprocess.call(["truncate", "-s", str(pow2), img])

This subprocess call is not very pythonic, so I've changed that to:

    with open(img, 'ab') as f:
        f.truncate(pow2)

Applied to master, thanks.

Regards,
Yann E. MORIN.

> -- 
> 2.31.1
> 
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