alexcekay opened a new pull request, #19126:
URL: https://github.com/apache/nuttx/pull/19126
## Summary
When a board switches storage technology but wants to mount a littlefs
filesystem onto this storage it is desired to still use the same firmware.
This almost works out of the box in NuttX with the exception of setting the
correct block size, which may be different depending on the used storage. An
incorrect block size may lead to suboptimal performance or worse.
To avoid writing a firmware variant that only differs by
CONFIG_FS_LITTLEFS_BLOCK_SIZE_FACTOR this adds the option to pass the intended
block size at the mount call. To still enable the usage of the existing options
this adds a parser for comma-separated mount options, allowing multiple options
to be passed simultaneously.
Example: "autoformat,block_size_factor=4",
"autoformat,block_size_factor=1"
This is backwards compatible: single options passed without commas continue
to work as before.
## Impact
This does not have an impact on existing users. The mount options they
currently pass still work as before.
## Testing
Tested on a v6s flight-controller (STM32H743VIH6) using the following test
mount options:
```
autoformat
forceformat
block_size_factor=1
block_size_factor=4
autoformat,block_size_factor=1
autoformat,block_size_factor=4
```
Those were passed at the mount call:
```
if (nx_mount(lfs_dev, "/fs/microsd", "littlefs", 0, <mount_options>) != 0)
```
Afterwards a breakpoint was set after the parser code and the values of the
variables `autoformat`, `forceformat` and `block_size_factor` were checked for
correctness. After that it was ensured that the filesystem mounts correctly.
The obvious edge-case is:
```
block_size_factor=0
```
This causes a div by zero in the calculation of `fs->cfg.block_count`. This
however was already the case before with
`CONFIG_FS_LITTLEFS_BLOCK_SIZE_FACTOR`, so I did not add an additional
verification as this will directly be visible on the first mount try.
Another edge-case is:
```
autoformat,forceformat
```
This semantically does not make much sense but does not cause any real
problems as the two options can co-exist. In this case `forceformat` is
executed first. If for some reason the mounting would still fail even after
that format with `EFAULT` then `autoformat` would format again.
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