Linux SPI总线 - SPI协议驱动层

Posted 2021-09-01 四季帆

        以ymu836这款音频编解码芯片的驱动为例：

static struct spi_driver ymu836_spi_driver = {
        .driver = {
                .name = "ymu836",
                .owner = THIS_MODULE,
                .of_match_table = ymu836_of_match,
        },
        .probe =    ymu836_spi_probe,
        .remove =   ymu836_spi_remove,
        .shutdown = ymu836_spi_shutdown,
        .id_table = ymu836_spi_id,
};
module_spi_driver(ymu836_spi_driver);

static int ymu836_spi_probe(struct spi_device *spi)
{
        int ret;
        
        ymu836 = devm_kzalloc(&spi->dev, sizeof(struct ymu836_priv), GFP_KERNEL);
        if (ymu836 == NULL)
                return -ENOMEM;
        //spi->bits_per_word=16;//Setup SPI bus properties
        spi->mode=0;
        //spi->bits_per_word=16;      
        ret = spi_setup(spi);   //调用spi通用接口层接口spi_setup()来设置spi控制器的模式和参数
        spi_set_drvdata(spi, ymu836);
        spidev=spi;
        ret = snd_soc_register_codec(&spi->dev,&soc_codec_dev_ymu836, &ymu836_dai, 1);

        return ret;
}

        譬如ymu386芯片的驱动程序提供的读方法，就是使用spi通用接口层的接口和数据结构类型来实现的。

int ymu836_spi_read(unsigned char uCom, unsigned char *puData,unsigned long uSize)
{
        int ret=0,len=0;
        struct spi_transfer t[1] = {};   /* 定义一个spi_transfer结构 */
        struct spi_message m;     /* 定义一个spi_message结构 */
        unsigned char txData[1024],rxData[1042];

        spi_message_init(&m);     /* 初始化spi_message */
        memset(txData,0,1024);
        memset(rxData,0,1024);
        txData[0]=uCom;
        /* 为数据准备缓冲区并赋值给spi_transfer相应的字段（tx_buf，rx_buf等） */
        t[0].tx_buf = txData;
        t[0].rx_buf = rxData;
        t[0].len = uSize+1;
        /* 把spi_transfer挂在spi_message结构下 */
        spi_message_add_tail(&t[0], &m);
        /* 如果使用同步方式传输数据，调用spi_sync() */
        spi_sync(spidev, &m);
        len += m.actual_length - 1;
        return ret;
}