egd_get_numch - Get the number of channels sampled by type
int egd_get_numch(const struct eegdev* dev, int
egd_get_numch() returns the number of channels of type stype
sampled by the recording device referenced by dev. stype must be
one of the values returned by egd_sensor_type(3).
In case of success, the function returns a non negative value corresponding to
the number of channels of type stype (possibly 0 if the device does not
sample this type of data). Otherwise, -1 is returned and errno is set
egd_get_numch() will fail if:
- dev is NULL or stype is not valid value.