mixer: remove volume backwards compat, add % interpretation

[kevans]

Summary

The current situation is fairly confusing, where an integer is interpreted
as a percent until you slap a decimal on it and magically it becomes an
absolute value.

Let's have a flag day in 14.0 and remove this shim entirely. Setting with
percent can still be useful, so allow a trailing '%' to indicate as such.
As a side effect, we tighten down the format allowed in the volume a little
bit by ensuring there's no trailing garbage after the value once it's
separated into left and right components.

Relnotes: yes

[pauamma_gundo.com]

usr.sbin/mixer/mixer.8

133

Percent of what? Is "70%" the same as absolute 0.7, 0.7 times whatever the current value is, or something else?

[kevans]

usr.sbin/mixer/mixer.8

133

Right, the intended interpretation is "70% of 1.0"

usr.sbin/mixer/mixer.c

358–359

It occurred to me that this is likely wrong, or that rrel needs to be reset later if n > 1. I suspect the right answer is that this should just set lrel = 1; and we should handle rrel = lrel down where we handle v.right = v.left (inside the switch)

[• hselasky]

I have no objections for this patch, specifying percentage with "%" else it is relative to 1.0.

Let me know when the patch is ready to land.

Christos?

--HPS

[pauamma_gundo.com]

usr.sbin/mixer/mixer.8

131–136

More readily understandable. (Insert line break where appropriate.)

133–134

Clarify.

140–145

Are +23% or -42% also possible? I would add examples here if so, along the lines of (if I understand the intent correctly):

If the volume is currently 0.707, then`mixer volume '+23%' followed by 'mixer volume '-42%'` will set it first to 0.869, then to 0.486.

[• hselasky]

There are some rc.d / devd scripts in base which needs fixing. Just
grep -ri mixer /usr/src

Can you include those deltas too, Kyle?

[christos]

Getting rid of the backwards compatibility which allows for both normalized
floats and the 0-100 OSS values is a good idea.

I think it's important to document that with relatives volume changes, the
percentage still uses 1.0 as a reference. For example, mixer vol=-5% doesn't
mean that the volume is decreased 5% relative to what the volume already was,
but 5% relative to 1.0 (or at least that's what the code does). This could create
some confusion.

[christos]

usr.sbin/mixer/mixer.8

131–136

Why 6 decimal digits? Since OSS' internal values range from 0 to 100, it makes
sense to use only 2 decimal digits, as we already do. Or am I missing
something?

140–145

I pointed this out on my comment as well. Although it does make sense, I think
-23% being relative to the current volume can be a bit confusing.

[kevans]

Highlights:

• Fix devd scripts
• Fix other examples found in the tree
• Fix rrel inheriting lrel prematurely
• Don't allow garbage after %, either

usbhidaction has an example using awk that I simplified to just
setting the absolute value rather a percentage.

[christos]

LGTM!

[pauamma_gundo.com]

Will re-review the manual page as needed once there's consensus on the proper behavior.

usr.sbin/mixer/mixer.8

131–136

That was me trying to clarify "32-bit float", which does give you 6-7 decimal digits IIRC. But maybe I was overly literal here.

140–145

Relative to the current volume feels more natural to me, but then I don't think I've ever used that volume-setting interface, so POLA overall probably dictates "document clearly what the code actually does, not change the code to fit one person's preconceptions".

[pauamma_gundo.com]

In D35101#795642, @pauamma_gundo.com wrote:

Will re-review the manual page as needed once there's consensus on the proper behavior.

Which it looks like there is now, upon closer reading.

[christos]

Bump.

[• hselasky]

kevans@ Who are we waiting for?

[christos]

One more bump for good measure. :-)

[• hselasky]

Ping - are we good to go?

[kevans]

Sorry, I'll take care of this soon.