[ltp] Re: [PATCH] Set osi=Linux for the ThinkPad X200s

[Henrique de Moraes Holschuh]

On Thu, 26 Nov 2009, Pedro Ribeiro wrote:
> I beg to differ.
> 
> All laptops I've seen to do that use the mute key to unmute (Lenovo,
> Sony, HP, Asus, Acer,...).  In fact, I can't think of a single one

You are correct.

But be advised that many of us looks at it this way : The inferior machines
(read: most non-thinkpads, and the thinkpads-only-in-name like the i-Series
and the SL-series) all implement muting in the cheap.

Which of the laptops you mention have the volume and mute/unmute keys work
while on the BIOS, or when the OS is still loading, or during a OS crash?

ThinkPads have _always_ been on a class of their own.  The EC-based audio
mixer recently lost the volume control to reduce power comsumption, but it
got a MIC mute function later on (which is a damn good idea).

> manufactured since 2004 which has the behaviour you describe.

All ThinkPads up to the Z60 have mute-always-mutes behaviour.  Those
certainly have been manufactured after 2004.

> I also think that is expected behaviour - why should I have to press
> volume up to unmute sound? I don't want the sound a notch up, I want
> it exactly at the same volume as it was before being muted.

Because that means if you press mute, it *always* mutes.  Even if you are
blind and cannot see the "is it mute?" led.  Even if you have no
recollection whether the sound is mute or not right now, and there is
nothing playing.  Even if the operating system has not finished loading yet,
or crashed, or is just too damn slow to process the keys in software right
now.

Also, when in a panic because you KNOW it is going to play something you
REALLY don't want out in the open in the next second, you can just hit mute,
before it manages to embarass you during a business meeting or presentation.

It is also done on the embedded controller, which is powered up and running
even if the main CPU crashes (on a Lenovo ThinkPad, it is powered for as
long as there is a battery phisically connected, even.  That thing draws a
few microwatts when on sleep mode, if not less...).

So the mute/unmute control (and the volume control, on the IBM thinkpads) is
available from the instant you touch the power button.

> With my T400 and without OSI(Linux) I can't use mute or volume down to
> unmute, I have to notch up the volume with the volume up key. Very
> annoying.

The first press of volume up/down when the thinkpad is mute does NOT change
volume level, unless either you our your Linux distro took steps to break
it.  It just unmutes.

You want it MUTE, press mute.
You want it UNMUTE?  press mute and a volume key.

No need to know the previous state.  No side-effects.

> Oh and even with acpi_osi=Linux I can't get the headphone output mute.
> Anyone has the same behaviour on the T400?

The line-out is for production work on IBM laptops (never mind the D/A and
analog circuitry are nowhere good enough for professional use), the laptop
volume and mute doesn't affect it, and firmware beeps do NOT go through it.
So, if it starts beeping or you change volume in the "monitor" channel
(headphone, speakers), the output over line-out (which you might be
recording or broadcasting or whatever) is not affected.

I don't think that's strictly true on Lenovo ThinkPads, and they might even
have decided that the keys should only relate to the speakers (which I would
consider a design bug).

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh