借此Machine驱动了解了ALSA on Soc的Machine驱动。这是一个简单版本的。

rk_dummy.c

/*
*  rk_dummy.c  --  SoC audio for rockchip
*
*  Driver for rockchip dummy audio
*  based: 7aca69f9fe8f04ca37a01e2540960c53b24e3223 patch
*
*  This program is free software; you can redistribute  it and/or modify it
*  under  the terms of  the GNU General  Public License as published by the
*  Free Software Foundation;  either version 2 of the  License, or (at your
*  option) any later version.
*
*/
#include <linux/module.h>
#include <linux/device.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/soc.h>
#include <sound/soc-dapm.h>
#include <asm/io.h>
#include <mach/hardware.h>

static struct snd_soc_dai_link rk_dai[] = {
	{
		.name = "RK616 I2S2",
		.stream_name = "RK616 PCM",
		.codec_name = "snd-soc-dummy.0",
		.platform_name = "snd-soc-dummy",
		.cpu_dai_name = "rk29_i2s.1",
		.codec_dai_name = "snd-soc-dummy-dai",
	},
};

static struct snd_soc_card snd_soc_card_rk = {
	.name = "RK_RK616",
	.dai_link = rk_dai,
	.num_links = ARRAY_SIZE(rk_dai),
};
static struct platform_device *rk_snd_device;

static int __init audio_card_init(void)
{
	int ret = 0;

	printk("Enter::%s----%d\n",__FUNCTION__,__LINE__);

	rk_snd_device = platform_device_alloc("soc-audio", -1);
	if (!rk_snd_device) {
		  printk("platform device allocation failed\n");
		  return -ENOMEM;
	}

	platform_set_drvdata(rk_snd_device, &snd_soc_card_rk);
	ret = platform_device_add(rk_snd_device);
	if (ret) {
		printk("platform device add failed\n");

		platform_device_put(rk_snd_device);
		return ret;
	}
	
    return ret;
}

static void __exit audio_card_exit(void)
{
	platform_device_unregister(rk_snd_device);
}

module_init(audio_card_init);
module_exit(audio_card_exit);
/* Module information */
MODULE_AUTHOR("rockchip");
MODULE_DESCRIPTION("ROCKCHIP i2s ASoC Interface");
MODULE_LICENSE("GPL");

报错如下：
<3>[ 834.123305] soc-audio soc-audio: ASoC: CPU DAI rk29_i2s.1 not registered

为什么rk29_i2s.1没有注册呢？大拿，能给个通过alsa驱动startup控制驱动demo吗？非常感谢！