Commits on Nov 12, 2024

1. hd-image: add support for specifying byte value used for filling …

   Today I was fooled by the combination of (1) util.c being quite
   clever/aggressive with respect to creating sparse images and avoiding
   writing zeroes explicitly and (2) using bmaptool to populate an SD
   card, thus being aware of unwritten regions of the image.
   
   Specifically, I had a U-Boot environment partition where I now set
   "fill = true", so that any trace of the previous environment should be
   gone, and U-Boot on first boot should just use its default/static
   environment.
   
   But that was not what I observed: After writing the sd card, the
   U-Boot partition still has its old content, meaning that the new
   U-Boot ended up using a completely wrong environment.
   
   In order to be sure that such a partition is definitely overwritten,
   allow specifiyng the byte value used for filling. Any non-zero value
   should work fine.
   
   Alternatively/additionally, we could consider relaxing the sparseness,
   so that, say, the first 4096 bytes of the padding are always
   explicitly written. But I don't know if bmaptool is so "smart" that it
   checks whether it has a full 4096 bytes of zeroes and then turning
   that into a sparse write anyway.
   
   Signed-off-by: Rasmus Villemoes <[email protected]>

   

   ravi-prevas committed Nov 12, 2024
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