I think headphones is the left-side phono jack, line-out is the middle phono jack, and microphone input is the right-side phono jack.

# linux 3.8.0-26-generic
//never been plugged:
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//plug in speaker phono
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = Yes
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//unplugged:
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//plug in line-out phono
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = Yes
Pin 0x21 (Black SPDIF Out): present = No
//unplugged:
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//plug in mic-in phono
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = Yes
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//unplugged
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No

# linux 3.10.0-2-generic
//never been plugged:
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//plug in speaker phono
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = Yes
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//unplugged:
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//plug in line-out phono
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = Yes
Pin 0x21 (Black SPDIF Out): present = No
//unplugged:
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//plug in mic-in phono
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = Yes
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No
//unplugged
Sigmatel specific "Analog Loopback: 0x00" verb ignored for the moment
Pin 0x0a (Black HP Out): present = No
Pin 0x0e (Black Line In): present = No
Pin 0x0f (Black Line Out): present = No
Pin 0x21 (Black SPDIF Out): present = No