[Development report #35] Audio Stack Improvements

Automatic audio redirection

	- sound: Access softc through si_drv1 in dsp cdev methods:
	  https://reviews.freebsd.org/D49804
	- sound: Create a dsp_close() helper function:
	  https://reviews.freebsd.org/D49805
	- sound: Implement /dev/dsp as a router device:
	  https://reviews.freebsd.org/D49216
		- Do not ignore return values in vdsp cdev methods.
		- Discussion on call-for-testing email:
		  https://lists.freebsd.org/archives/freebsd-multimedia/2025-April/002944.html
		- Remove unit argument from vdsp_open_dev() and
		  vdsp_get_dev() and figure it out inside the functions
		  instead. It's cleaner in combination with the
		  follow-up patch.
		- Depend on D49804 and D49805.
		- Addressing new recent comments.
		- Testing new changes.
	- Split the default unit into playback and recording
		- I delayed submitting the patch for review, because
		  I've been rewriting and testing it the past few days,
		  after some design issues I hadn't considered.

Laptop project

	- Updated Github issue:
	  https://github.com/FreeBSDFoundation/proj-laptop/issues/17
	- Attended LDWG call.
	- Attended Foundation's Iteration call.
	- Did some HDA debugging with adrian@ on IRC.

audio(8): Initial revision:
https://reviews.freebsd.org/D46227

Status/2025Q1/audio.adoc: Add report:
https://cgit.freebsd.org/doc/commit/?id=20a50568c34dc2f1dcc85ca4b22d33dd5f72fdbb

Bug reports:

	- https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=285962
	- https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=261693
	- https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=278806
	- Closed AFMT_FLOAT PRs after MFC to stable/14: 157050, 184380,
	  280612, 281390.
	- Triaging.

In contact with Meka <meka@tilda.center> about adding an mmap audio
example program to /usr/share/examples/sound/oss.

MFC'd recent patches to stable/14.

Purchased BSDCan DevSummit ticket.

Christos

This work is sponsored by the FreeBSD Foundation.