[Bug 157050] OSS implementation lacks AFMT_FLOAT

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

--- Comment #7 from commit-hook@FreeBSD.org ---
A commit in branch main references this bug:

URL:
https://cgit.FreeBSD.org/src/commit/?id=e1bbaa71d62c8681a576f9f5bedf475c7541bd35

commit e1bbaa71d62c8681a576f9f5bedf475c7541bd35
Author:     Christos Margiolis <christos@FreeBSD.org>
AuthorDate: 2025-03-30 17:45:38 +0000
Commit:     Christos Margiolis <christos@FreeBSD.org>
CommitDate: 2025-03-30 17:45:38 +0000

    sound: Implement AFMT_FLOAT support

    Even though the OSS manual [1] advises against using AFMT_FLOAT, there
    are applications that expect the sound driver to support it, and might
    not work properly without it.

    This patch adds AFMT_F32_LE|BE (as well as AFMT_FLOAT for OSS
    compatibility) in sys/soundcard.h and implements AFMT_F32_LE|BE <->
    AFMT_S32_LE|BE conversion functions. As a result, applications can
    write/read floats to/from sound(4), but internally, because sound(4)
    works with integers, we convert floating point samples to integer ones,
    before doing any processing.

    The reason for encoding/decoding IEEE754s manually, instead of using
    fpu_kern(9), is that fpu_kern(9) is not supported by all architectures,
    and also introduces significant overhead.

    The IEEE754 encoding/decoding implementation has been written by Ariff
    Abdullah [2].

    [1] http://manuals.opensound.com/developer/AFMT_FLOAT.html
    [2] https://people.freebsd.org/~ariff/utils/ieee754.c

    PR:             157050, 184380, 264973, 280612, 281390
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Reviewed by:    emaste
    Differential Revision:  https://reviews.freebsd.org/D47638

 sys/dev/sound/pcm/channel.c       |  4 +++
 sys/dev/sound/pcm/feeder_chain.c  |  2 ++
 sys/dev/sound/pcm/feeder_rate.c   |  4 +++
 sys/dev/sound/pcm/feeder_volume.c |  2 ++
 sys/dev/sound/pcm/pcm.h           | 67 +++++++++++++++++++++++++++++++++++++--
 sys/dev/sound/pcm/sound.h         | 13 +++++---
 sys/sys/soundcard.h               |  8 +++++
 tests/sys/sound/pcm_read_write.c  |  6 ++++
 8 files changed, 98 insertions(+), 8 deletions(-)

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