Question

我正在尝试使用ALSA开发声卡驱动程序。我的目标最终是使用：

PCM通过I2S。
通过SPI控制音量。

为简单起见，我开始只进行音量控制，没有PCM。我写了驱动程序并编译但我有两个问题：

我无法在模块出口中成功调用snd_card_free。我尝试存储snd_card指针，该指针在我的自定义＆＃34; snd_adsp21479_chip＆＃34;中的模块init中成功分配。结构并使用container_of来获取snd_card，但是module_exit中的卡总是为null（在module_init中它不是null并且已成功分配，我有检查，我也可以在模块init函数中成功调用snd_card_free（card），但没有其他地方）。因此，每次我将模块重新加载到内核时，我最终会在/ dev / snd /和proc / asound / devices中再添加一个声卡和一个新控件
我现在最大的问题是在加载模块后我确实在/ dev / snd /中看到一个新控件（control1）和一张新卡，但是使用amixer我看不到卡的音量控制。我运行amixer conctrols，我没有看到我的新控件。

以下是代码：

#include <linux/wait.h>
#include <sound/control.h>
#include <sound/core.h>
#include <sound/initval.h>
#include <linux/spi/spi.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/platform_device.h>

#define LOW_SPEED_SPIDEV_SPI_BUS 0
#define LOW_SPEED_SPIDEV_SPI_CS 0
#define LOW_SPEED_SPIDEV_MAX_CLK_HZ 100000
#define SOUND_CARD_NAME "adsp21479"

static struct spi_board_info cal_spi_board_info  = {
        .modalias       = "spidev",
        .bus_num        = LOW_SPEED_SPIDEV_SPI_BUS,
        .chip_select    = LOW_SPEED_SPIDEV_SPI_CS,
        .max_speed_hz   = LOW_SPEED_SPIDEV_MAX_CLK_HZ,
};


static struct spi_device *spi = NULL;
struct snd_adsp21479_chip {
    struct spi_device   *spi;
    struct snd_card     *card;   
};



/*******************************CONTROL METHODS *******************************/
static int snd_adsp21479_stereo_info(struct snd_kcontrol *kcontrol,
        struct snd_ctl_elem_info * uinfo)
{
    uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
    uinfo->count = 2; 
    uinfo->value.integer.min = 0;
    uinfo->value.integer.max = 100;
    return 0;

}

static int snd_adsp21479_stereo_get(struct snd_kcontrol *kcontrol,
        struct snd_ctl_elem_value *ucontrol)
{

    return 0;
}

static int snd_adsp21479_stereo_put(struct snd_kcontrol *kcontrol,
        struct snd_ctl_elem_value *ucontrol)
{
    return 0;


}

static struct snd_kcontrol_new volume_control = {
    .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
    .name = "PCM Playback Volume",
    .index = 0,
    .access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
    .info = snd_adsp21479_stereo_info,
    .get = snd_adsp21479_stereo_get,
    .put = snd_adsp21479_stereo_put

};




static int snd_adsp21479_init(struct spi_device *spi)
{
    struct snd_card * card = NULL;
    int return_value;

    char id[10] = SOUND_CARD_NAME;
    struct snd_adsp21479_chip *chip;
    pr_info("snd_adsp21479_init start\n");

    return_value = snd_card_new(&spi->dev,-1,id,THIS_MODULE,sizeof(struct snd_adsp21479_chip),&card);
    if(return_value<0)
    {
        pr_err("snd_card_new failed\n");
        return return_value;
    }


    if(!card)
    {
        pr_err("snd_card_new did not allocate card");
        return -ENODEV;
    }


    pr_info("sound card=%p created successfully",card);


    chip = card->private_data;

    chip->card = card;    
    chip->spi = spi;

    strcpy(card->mixername,"adsp21479 Mixer");

    return_value = snd_ctl_add(card,snd_ctl_new1(&volume_control,chip));
    if(return_value<0)
    {
        pr_err("snd_ctl_add faile adding control\n");
        return return_value;    
    }   

    pr_info("created a mixer control");

    static struct snd_device_ops ops = { NULL};


    strcpy(card->driver,SOUND_CARD_NAME);
    strcpy(card->shortname,SOUND_CARD_NAME);
    strcpy(card->longname,"DAQRI ADSP21479 Sound Driver");

    //create an ALSA device component
    return_value = snd_device_new(card, SNDRV_DEV_LOWLEVEL,chip,&ops);

    if(return_value<0)
    {
        printk(KERN_ALERT"creating an ALSA device component failed");
        return return_value;

    }

    pr_info("created an ASLA device SNDRV_DEV_LOWLEVEL");   

    return_value = snd_card_register(card);

    if(return_value<0)
    {
        pr_err("snd_card_register failed\n");
        return return_value;  
    }

    if(!card)
    {
        pr_err("card turned into null\n");
    }

    pr_info("registered sound card\n");

    pr_info("adsp21479_snd_driver loaded successfully\n");
    return 0;
  // card here is always ok, and if I call snd_card_free(card) here it works.
}

static int __init adsp21479_spi_module_init(void)
{
    struct spi_master *master=NULL;
    int err;

    pr_info("module init\n");

    err = -ENODEV;

    master = spi_busnum_to_master(LOW_SPEED_SPIDEV_SPI_BUS);
    pr_info("master=%p\n", master);
    if (!master)
    {
        pr_err("spi_busnum_to_master failed");
        return err;           
    }        

    spi = spi_new_device(master, &cal_spi_board_info);
    pr_info("spi device =%p\n", spi);
    if (!spi)
    {
        pr_err("spi_new_device failed");
        return err;
    }

    pr_info("spi device registered\n");
    err = 0;

    return snd_adsp21479_init(spi);

}

static void __exit adsp21479_spi_module_exit(void)
{

    struct snd_adsp21479_chip *chip;
    pr_info("module exit");
    if (spi)
    {
        chip = container_of(&spi,struct snd_adsp21479_chip,spi);

        if(chip)
        {
            pr_info("chip is not null\n");

            if(chip->spi == spi)
            {
                pr_info("spi match\n");
            }
            pr_info("card = %p",chip->card);
            if(chip->card != NULL) 
            {
                pr_info("freeing sound card=%p\n",chip->card); // I never get here, it's always null, or if I store card in a global variable, I get an exception. And if I store it with drv_set_drvdata(&spi->dev,card) in the init function and try to obtain it here with a dev_get_drvdata(&spi->dev); and try to free the card with snd_card_free I get an exception as well.
                snd_card_free(chip->card);
            }
        }


        pr_info("unregistering spi device\n");
        spi_unregister_device(spi);
    }
}


module_init(adsp21479_spi_module_init);
module_exit(adsp21479_spi_module_exit);




/***************************SPI DRIVER METHODS  ****************************/


MODULE_LICENSE("GPL"); ///WE NEED TO CHANGE IT LATER MAYBE
MODULE_DESCRIPTION(" Sound driver for the ADSP-21479");

重申一点：这里没有PCM，我只是试图通过SPI来控制音量，而我的控制器并没有显示在amixer中，我也无法释放我的卡。我使用spidev作为SPI BUS主站，此驱动程序用于声卡SPI从站。

ALSA声卡驱动程序无法调用snd_card_free（..）并且amixer无法看到控件

0 个答案: