usbaudioctl.h

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

enum{
	Undef = 0x80000000,
	Play = 0,
	Record = 1,
};

typedef struct Audiocontrol Audiocontrol;

struct Audiocontrol {
	char	*name;
	uchar	readable;
	uchar	settable;
	uchar	chans;		/* 0 is master, non-zero is bitmap */
	long	value[8];	/* 0 is master; value[0] == Undef -> all values Undef */
	long	min, max, step;
};

extern Audiocontrol controls[2][Ncontrol];
extern int endpt[2];
extern int interface[2];
extern int featureid[2];
extern int selectorid[2];
extern int mixerid[2];
extern int buttonendpt;

int	ctlparse(char *s, Audiocontrol *c, long *v);
void	ctlevent(void);

#pragma	varargck	type	"A"	Audiocontrol*