extmod/vfs_fat: Fallback to FAT32 during fat_vfs_mkfs if the standard FAT16/SFD format fails.

[andrewleech]

This allows formatting SD cards, larger flash etc which do not support the default FAT16/SFD format.

eg. import pyb, uos;uos.VfsFat.mkfs(pyb.SDCard())

I presume the default format was chosen for lower overheads when smaller flash spaces are used?

[dpgeorge]

I presume the default format was chosen for lower overheads when smaller flash spaces are used?

Yes.

Please see #3717 for an existing attempt at this, and comments there.

[andrewleech]

Ah yes, your comment there is exactly as I assumed for this patch.

I first attempt to format with the exact settings currently used, only if that fails with the error returned when fat16 isn't supported do I retry with fat32.

As such there should be zero change for anywhere the existing mkfs works.

[dpgeorge]

As such there should be zero change for anywhere the existing mkfs works.

Yes, it looks good, the patch here.

Also, probably makes sense to just update mkfs (as is done here) and not the "mkfs=True" option of mount, since that was there to support old behaviour of user-mountable block devices.

[dpgeorge]

Merged in 74d0746

[doc-hex]

This fix is incomplete. There is another call to f_mkfs() inside vfs_fat_mount() if mkfs=True. I hit this case recently.