ALSA: emu10k1: more documentation updates

- Clarify the data flows. For SB Live! I fixed only the most obvious
point ("from" vs. "for").
- Mention 7.1 side channels on Audigy.
- Be unspecific about the output DACs on Audigy, as lots of variants
actually exist (see emu_chip_details table).

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230825222157.170978-2-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: emu10k1: de-duplicate audigy-mixer.rst vs. sb-live-mixer.rst

Let the MANUALS/PATENTS section of the former simply refer to the latter
- there is no point in duplicating this information with little value to
end users.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230825222157.170978-1-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: emu10k1: straighten out FX send init

The mixer structures were filled in two places: on driver init, and when
the devices are opened. The latter made the former pointless, so we
remove the former. This implies that mixer dumps may now return all
zeroes, which is OK, as restoring them is meaningless as well.

Things were even weirder for the (generally unused) secondary sends:

Some of the initialization loops were forgotten when support for Audigy
was added, thus creating the technically illegal state of multiple sends
being routed to the same FX accumulator (though it apparently doesn't
matter when the amount is zero).

The global multi-channel init used some rather bizarre values for the
secondary sends, and the init on open actually forgot to re-initialize
them. We now use a not really more useful, but simpler formula.

The direct register init was also bogus. This doesn't really matter, as
the value is overwritten when a voice comes into use, but still.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230516093612.3536451-2-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: emu10k1: enable bit-exact playback, part 2: voice attenuation

The voice volume is a raw fractional multiplier that can't actually
represent 1.0. To still enable real pass-through, we now set the volume
to 0.5 (which results in no loss of precision, as the FX bus provides
fractional values) and scale up the samples in DSP code.

To maintain backwards compatibility with existing configuration files,
we rescale the values in the mixer controls. The range is extended
upwards from 0xffff to 0x1fffd, which actually introduces the
possibility of specifying an amplification.

There is still a minor incompatibility with user space, namely if
someone loaded custom DSP code. They'll just get half the volume, so
this doesn't seem like a big deal.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230514170323.3408834-8-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: emu10k1: documentation updates

- Less misinformation
- Language and whitespace fixups

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230405201220.2197893-1-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Documentation: sound: correct spelling

Correct spelling problems for Documentation/sound/ as reported
by codespell.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: alsa-devel@alsa-project.org
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Link: https://lore.kernel.org/r/20230127064005.1558-27-rdunlap@infradead.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Documentation: sound/cards: fix heading underline lengths for https: changes

Fix documentation build warnings for underline length too short,
caused by s/http/https/ and not changing the accompanying underlines.

Documentation/sound/cards/audigy-mixer.rst:335: WARNING: Title underline too short.
US Patents (https://www.uspto.gov/)
----------------------------------

Documentation/sound/cards/sb-live-mixer.rst:340: WARNING: Title underline too short.
US Patents (https://www.uspto.gov/)
----------------------------------

Fixes: 7ed33ea6b4fa ("ALSA: Replace HTTP links with HTTPS ones")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Alexander A. Klimov <grandmaster@al2klimov.de>
Link: https://lore.kernel.org/r/357ee576-32a2-6e2b-1db6-78be39253846@infradead.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: Replace HTTP links with HTTPS ones

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
If not .svg:
For each line:
If doesn't contain `\bxmlns\b`:
For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`:
If both the HTTP and HTTPS versions
return 200 OK and serve the same content:
Replace HTTP with HTTPS.

Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Link: https://lore.kernel.org/r/20200719151705.59624-1-grandmaster@al2klimov.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: doc: ReSTize Audigy-mixer.txt

Another simple conversion from a plain text file.
Put to cards subdirectory.

Signed-off-by: Takashi Iwai <tiwai@suse.de>