sound connector detection

[Johannes Berg]

Hi,

One Apple machines I have with snd-aoa the situation that the alsa
driver can detect changes in in/output connector state ("is headphone
plugged in" etc.) and currently surfaces it through a read-only alsa
mixer element. That isn't really ideal since nothing is prepared to
handle such events, hence I provide an additional control that allows an
in-kernel toggle from speakers to headphone on headphone plug (and vice
versa).

I'd really like to see this handled in userspace (additionally or
possibly event instead), since there are complications especially with
input (line-in) detection and user preferences of what should happen
then. The number of cases can become large, especially when throwing in
digital and combo connectors that aren't handled yet.

Now, is it appropriate to create an input device for the state of these
things and add new constants like SW_LINEIN_INSERTED,
SW_LINEOUT_INSERTED, SW_OPTICALOUT_INSERTED, SW_OPTICALIN_INSERTED and
if so, how do I reflect the fact that on some machines optical and
analog input/output is mutually exclusive, while on others it isn't?
That would probably require another SW_COMBO_IN/OUT set...

Or should I simply stick with (a) read-only mixer control(s), and for
the mutually exclusive case create a tristate (none, optical, analog)
one? But SW_HEADPHONE_INSERT already exists, so we may want to do this
identically on different machines.

Comments appreciated.

johannes
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