Bug 281390

Summary:	sound: OSS have no AFMT_FLOAT support
Product:	Base System	Reporter:	Ivan Rozhuk <rozhuk.im>
Component:	kern	Assignee:	Christos Margiolis <christos>
Status:	Open ---
Severity:	Affects Some People	CC:	agh, bsdcode, christos, emaste, markj, rozhuk.im, sascha.folie
Priority:	---
Version:	Unspecified
Hardware:	Any
OS:	Any
See Also:	https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=157050 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=264973
Bug Depends on:
Bug Blocks:	280612

Description Ivan Rozhuk 2024-09-09 12:38:33 UTC

Past issues:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=157050
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=184380

In the wild some software from ports that have OSS support just define AFMT_FLOAT inside own code.

AFMT_FLOAT used in wine: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=264973
Currently as workaround wine builds with ALSA.


I suggest to add some in kernel conversion from AFMT_FLOAT to some thing that aleady support by "PCM subsystem mixing through its feeder subsystem" or update feeder subsystem to support AFMT_FLOAT.

Comment 1 Mark Linimon freebsd_committer

2024-09-30 05:45:30 UTC

^Triage: I don't see a proposed solution yet, so "In Progress" may be premature.

Comment 2 Christos Margiolis freebsd_committer

2024-09-30 15:22:43 UTC

(In reply to Mark Linimon from comment #1)
I am working on it.

Comment 3 Christos Margiolis freebsd_committer

2024-11-16 18:15:54 UTC

https://reviews.freebsd.org/D47638

Comment 4 Ivan Rozhuk 2024-11-18 22:35:47 UTC

Thanks!

Probably you can avoid fpu_kern_**() staff.

https://stackoverflow.com/questions/10212892/how-to-avoid-fpu-when-given-float-numbers
https://www.jhauser.us/arithmetic/SoftFloat.html

https://stackoverflow.com/questions/78619/what-is-the-fastest-way-to-convert-float-to-int-on-x86

https://stackoverflow.com/questions/68258170/fastest-way-to-convert-a-float-to-int-in-c

https://medium.com/@ryan_forrester_/c-float-to-int-conversion-how-to-guide-aea5be6d3d4b

Comment 5 Ivan Rozhuk 2024-11-18 22:42:41 UTC

http://0x80.pl/articles/convert-float-to-integer.html

https://onestepcode.com/float-to-int-c/

Comment 6 Ed Maste freebsd_committer

2024-11-19 16:01:26 UTC

(In reply to Ivan Rozhuk from comment #4)
Note that we need not plain float->int but rather (float*constant)->int; this could be done with integer instructions but either way this should be something we look at after profiling if the overhead of fpu_kern_enter/_leave is excessive.

Comment 7 Ivan Rozhuk 2024-11-19 17:51:20 UTC

(In reply to Ed Maste from comment #6)

(float*constant)->int -> float->(int*constant) ? :)

As described in http://0x80.pl/articles/convert-float-to-integer.html float to int conversion should be not so expensive as fpu_kern_**() staff.

Also their code simple and under BSD2 license.