[alsa-devel] What's the deal with elements?

Borg Onion borg.onion at gmail.com
Wed Nov 23 05:44:03 CET 2011


Still writing some basic ALSA software, trying to get to know the API.  I
wrote some software to list cards and their properties, with output like

$ ./list
Card #0: id=ICH6, driver=ICH4, name=Intel ICH6, longname=Intel ICH6 with
AD1981B at irq 17, mixername=Analog Devices AD1981B,
Element used = 0, count = 28
Power state = D0
CTL type = Kernel level CTL
Card #1: id=Device, driver=USB-Audio, name=C-Media USB Audio Device,
longname=C-Media USB Audio Device at usb-0000:00:1d.0-1, full speed,
mixername=USB Mixer, components=USB0d8c:0008
Element used = 0, count = 7
Power state = D0
CTL type = Kernel level CTL
No more cards!

Whenever I try to access the elements by their index though, I get errors.
 What's the meaning of "used" vs. "count"?  What are these elements used
for?  I would assume to discover what devices are on a card, but I could be
wrong.  How does one do device discovery?



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