Re: Questions about Unicode Normalization Form

[Matthew Wilcox <willy@infradead.org>]

On Sun, Apr 07, 2024 at 09:39:28PM -0400, Theodore Ts'o wrote:
> On Sat, Apr 06, 2024 at 11:15:36PM +0800, HAN Yuwei wrote:
> > 
> > Sorry, I am not very familiar with Unicode nor kernel. Correct me if wrong.
> > 
> > As to what I have read, kernel seems like using NFD when processing all
> > UTF-8 related string.
> > If fs is using these helper function, then I can be sure kernel is applying
> > NFD to every UTF-8 filenames.
> > But I can't find any references to these helper function on Github mirror,
> > how are they used by fs code?
> 
> For the most part, the kernel's file stysem code doesn't do anything
> special for Unicode.  The exception is that the ext4 and f2fs file
> systems can have an optional feature which is mostly only used by
> Android systems to support case insensitive lookups.  This is called
> the "casefold" feature, which is not enabled by default by most
> desktop or server systems.

As I understand it, an important usecase for the casefold feature is
running Windows games under WINE.  I don't do this myself (sgt-puzzles
is more my speed), but there's a pretty important market for this.
Wasn't this why Gabriel was funded to work on it (eg commit b886ee3e778e)?
Or was that the Android usecase?