alsa音频架构1 - c++编程基础

no_llseek,
.poll = snd_ctl_poll, //轮询方法
.unlocked_ioctl = snd_ctl_ioctl, //命令控制
.compat_ioctl = snd_ctl_ioctl_compat, //32位兼容的命令控制
.fasync = snd_ctl_fasync, //同步方法
};

static const struct file_operations snd_ctl_f_ops =
{
.owner = THIS_MODULE,
.read = snd_ctl_read, //读方法
.open = snd_ctl_open, //打开方法
.release = snd_ctl_release, //释放方法
.llseek = no_llseek,
.poll = snd_ctl_poll, //轮询方法
.unlocked_ioctl = snd_ctl_ioctl, //命令控制
.compat_ioctl = snd_ctl_ioctl_compat, //32位兼容的命令控制
.fasync = snd_ctl_fasync, //同步方法
};这样就提供了应用层的接口方法了,比较重要的是命令控制方法,主要有以下控制命令

[cpp]

#define SNDRV_CTL_IOCTL_PVERSION _IOR('U', 0x00, int)//打印alsa版本
#define SNDRV_CTL_IOCTL_CARD_INFO _IOR('U', 0x01, struct snd_ctl_card_info)//获取声卡信息
#define SNDRV_CTL_IOCTL_ELEM_LIST _IOWR('U', 0x10, struct snd_ctl_elem_list)
#define SNDRV_CTL_IOCTL_ELEM_INFO _IOWR('U', 0x11, struct snd_ctl_elem_info)
#define SNDRV_CTL_IOCTL_ELEM_READ _IOWR('U', 0x12, struct snd_ctl_elem_value)
#define SNDRV_CTL_IOCTL_ELEM_WRITE _IOWR('U', 0x13, struct snd_ctl_elem_value)
#define SNDRV_CTL_IOCTL_ELEM_LOCK _IOW('U', 0x14, struct snd_ctl_elem_id)
#define SNDRV_CTL_IOCTL_ELEM_UNLOCK _IOW('U', 0x15, struct snd_ctl_elem_id)
#define SNDRV_CTL_IOCTL_SUBSCRIBE_EVENTS _IOWR('U', 0x16, int)
#define SNDRV_CTL_IOCTL_ELEM_ADD _IOWR('U', 0x17, struct snd_ctl_elem_info)
#define SNDRV_CTL_IOCTL_ELEM_REPLACE _IOWR('U', 0x18, struct snd_ctl_elem_info)
#define SNDRV_CTL_IOCTL_ELEM_REMOVE _IOWR('U', 0x19, struct snd_ctl_elem_id)
#define SNDRV_CTL_IOCTL_TLV_READ _IOWR('U', 0x1a, struct snd_ctl_tlv)
#define SNDRV_CTL_IOCTL_TLV_WRITE _IOWR('U', 0x1b, struct snd_ctl_tlv)
#define SNDRV_CTL_IOCTL_TLV_COMMAND _IOWR('U', 0x1c, struct snd_ctl_tlv)
#define SNDRV_CTL_IOCTL_POWER _IOWR('U', 0xd0, int)//还没支持
#define SNDRV_CTL_IOCTL_POWER_STATE _IOR('U', 0xd1, int)//电源状态

[cpp]
aconnect is a ut

alsa音频架构1 (十)