Man page 9 : snd_jack_set_key

snd_jack_set_key - Set a key mapping on a jack

int snd_jack_set_key(struct snd_jack *  jack , enum snd_jack_types  type , int  keytype );

jack
    The jack to configure

type
    Jack report type for this key

keytype
    Input layer key type to be reported

Map a SND_JACK_BTN_ button type to an input layer key, allowing reporting of keys on accessories via the jack abstraction. If no mapping is provided but keys are enabled in the jack type then BTN_n numeric buttons will be reported.

If jacks are not reporting via the input API this call will have no effect.

Note that this is intended to be use by simple devices with small numbers of keys that can be reported. It is also possible to access the input device directly - devices with complex input capabilities on accessories should consider doing this rather than using this abstraction.

This function may only be called prior to registration of the jack.

Zero if successful, or a negative error code on failure.