ASoC: Add more natural support for no-DMA DAIs

Since we can now support multiple platforms allow machines to not specify
a platform in a DAI link. Since the rest of the code requires that we have
a struct device for all objects we do this by substituting in a dummy
device that we register automatically.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
Acked-by: Liam Girdwood <lrg@ti.com>

sound/soc/soc-core.c

@@ -1299,6 +1299,7 @@ static int soc_bind_dai_link(struct snd_soc_card *card, int num)
 	struct snd_soc_codec *codec;
 	struct snd_soc_platform *platform;
 	struct snd_soc_dai *codec_dai, *cpu_dai;
+	const char *platform_name;
 
 	if (rtd->complete)
 		return 1;
@@ -1351,13 +1352,18 @@ static int soc_bind_dai_link(struct snd_soc_card *card, int num)
 			dai_link->codec_name);
 
 find_platform:
-	/* do we already have the CODEC DAI for this link ? */
-	if (rtd->platform) {
+	/* do we need a platform? */
+	if (rtd->platform)
 		goto out;
-	}
-	/* no, then find CPU DAI from registered DAIs*/
+
+	/* if there's no platform we match on the empty platform */
+	platform_name = dai_link->platform_name;
+	if (!platform_name)
+		platform_name = "snd-soc-dummy";
+
+	/* no, then find one from the set of registered platforms */
 	list_for_each_entry(platform, &platform_list, list) {
-		if (!strcmp(platform->name, dai_link->platform_name)) {
+		if (!strcmp(platform->name, platform_name)) {
 			rtd->platform = platform;
 			goto out;
 		}

sound/soc/soc-utils.c

@@ -13,6 +13,7 @@
  *  option) any later version.
  */
 
+#include <linux/platform_device.h>
 #include <sound/core.h>
 #include <sound/pcm.h>
 #include <sound/pcm_params.h>
@@ -55,3 +56,57 @@ int snd_soc_params_to_bclk(struct snd_pcm_hw_params *params)
 		return ret;
 }
 EXPORT_SYMBOL_GPL(snd_soc_params_to_bclk);
+
+static struct snd_soc_platform_driver dummy_platform;
+
+static __devinit int snd_soc_dummy_probe(struct platform_device *pdev)
+{
+	return snd_soc_register_platform(&pdev->dev, &dummy_platform);
+}
+
+static __devexit int snd_soc_dummy_remove(struct platform_device *pdev)
+{
+	snd_soc_unregister_platform(&pdev->dev);
+
+	return 0;
+}
+
+static struct platform_driver soc_dummy_driver = {
+	.driver = {
+		.name = "snd-soc-dummy",
+		.owner = THIS_MODULE,
+	},
+	.probe = snd_soc_dummy_probe,
+	.remove = __devexit_p(snd_soc_dummy_remove),
+};
+
+static struct platform_device *soc_dummy_dev;
+
+static int __init snd_soc_util_init(void)
+{
+	int ret;
+
+	soc_dummy_dev = platform_device_alloc("snd-soc-dummy", -1);
+	if (!soc_dummy_dev)
+		return -ENOMEM;
+
+	ret = platform_device_add(soc_dummy_dev);
+	if (ret != 0) {
+		platform_device_put(soc_dummy_dev);
+		return ret;
+	}
+
+	ret = platform_driver_register(&soc_dummy_driver);
+	if (ret != 0)
+		platform_device_unregister(soc_dummy_dev);
+
+	return ret;
+}
+module_init(snd_soc_util_init);
+
+static void __exit snd_soc_util_exit(void)
+{
+	platform_device_unregister(soc_dummy_dev);
+	platform_driver_unregister(&soc_dummy_driver);
+}
+module_exit(snd_soc_util_exit);