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  • struct snd_soc_dai_ops接口介绍

    CPU DAI和codec DAI 驱动用结构体 struct snd_soc_dai_driver描述,其字段ops的类型是 struct snd_soc_dai_ops,定义了DAI驱动的操作接口。
    代码如下:

    struct snd_soc_dai_ops {
    	/*
    	 * DAI clocking configuration, all optional.
    	 * Called by soc_card drivers, normally in their hw_params.
    	 */
    	int (*set_sysclk)(struct snd_soc_dai *dai,
    		int clk_id, unsigned int freq, int dir);
    	int (*set_pll)(struct snd_soc_dai *dai, int pll_id, int source,
    		unsigned int freq_in, unsigned int freq_out);
    	int (*set_clkdiv)(struct snd_soc_dai *dai, int div_id, int div);
    	int (*set_bclk_ratio)(struct snd_soc_dai *dai, unsigned int ratio);
    
    	/*
    	 * DAI format configuration
    	 * Called by soc_card drivers, normally in their hw_params.
    	 */
    	int (*set_fmt)(struct snd_soc_dai *dai, unsigned int fmt);
    	int (*xlate_tdm_slot_mask)(unsigned int slots,
    		unsigned int *tx_mask, unsigned int *rx_mask);
    	int (*set_tdm_slot)(struct snd_soc_dai *dai,
    		unsigned int tx_mask, unsigned int rx_mask,
    		int slots, int slot_width);
    	int (*set_channel_map)(struct snd_soc_dai *dai,
    		unsigned int tx_num, unsigned int *tx_slot,
    		unsigned int rx_num, unsigned int *rx_slot);
    	int (*set_tristate)(struct snd_soc_dai *dai, int tristate);
    
    	/*
    	 * DAI digital mute - optional.
    	 * Called by soc-core to minimise any pops.
    	 */
    	int (*digital_mute)(struct snd_soc_dai *dai, int mute);
    	int (*mute_stream)(struct snd_soc_dai *dai, int mute, int stream);
    
    	/*
    	 * ALSA PCM audio operations - all optional.
    	 * Called by soc-core during audio PCM operations.
    	 */
    	int (*startup)(struct snd_pcm_substream *,
    		struct snd_soc_dai *);
    	void (*shutdown)(struct snd_pcm_substream *,
    		struct snd_soc_dai *);
    	int (*hw_params)(struct snd_pcm_substream *,
    		struct snd_pcm_hw_params *, struct snd_soc_dai *);
    	int (*hw_free)(struct snd_pcm_substream *,
    		struct snd_soc_dai *);
    	int (*prepare)(struct snd_pcm_substream *,
    		struct snd_soc_dai *);
    	/*
    	 * NOTE: Commands passed to the trigger function are not necessarily
    	 * compatible with the current state of the dai. For example this
    	 * sequence of commands is possible: START STOP STOP.
    	 * So do not unconditionally use refcounting functions in the trigger
    	 * function, e.g. clk_enable/disable.
    	 */
    	int (*trigger)(struct snd_pcm_substream *, int,
    		struct snd_soc_dai *);
    	int (*bespoke_trigger)(struct snd_pcm_substream *, int,
    		struct snd_soc_dai *);
    	/*
    	 * For hardware based FIFO caused delay reporting.
    	 * Optional.
    	 */
    	snd_pcm_sframes_t (*delay)(struct snd_pcm_substream *,
    		struct snd_soc_dai *);
    };
    
    1. DAI 时钟配置函数,通常由snd_card驱动即machine驱动的 hw_params函数调用
      set_sysclk 设置dai的主时钟
      set_pll 设置codec内PLL参数
      set_clkdiv 设置分频系数

    2. DAI 格式配置函数,通常由snd_card驱动即machine驱动的 hw_params函数调用
      set_fmt 设置dai的格式,例如主从模式、i2s或dsp模式等
      set_tdm_slot 设置DAI支持tdm时分复用,用来设置时分复用的slot,codec设备在第几个slot上读取数据。
      set_channel_map 声道的时分复用映射设置
      set_tristate 设置dai引脚的状态,当与其他dai并联使用同一引脚时需要使用该回调

    3. 标准的snd_soc_ops回调 通常由asoc core在进行PCM操作时调用
      startup
      shutdown
      hw_params
      hw_free
      prepare
      trigger

    4. 降低pop音,由asoc-core调用
      digital_mute

    soc-dai.h文件里定义的下面函数,通常在machine驱动 struct snd_soc_ops接口的hw_params()函数里 被调用,接收struct snd_soc_dai 实例参数。

    参考文档:
    https://blog.csdn.net/DroidPhone/article/details/7316061

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  • 原文地址:https://www.cnblogs.com/bobfly1984/p/14343034.html
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