[ALSA] Add pcm_class attribute to PCM sysfs entry

This patch adds a new attribute, pcm_class, to each PCM sysfs entry.
It's useful to detect what kind of PCM stream is, for example, HAL
can check whether it's a modem or not.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

include/sound/core.h

@@ -26,6 +26,7 @@
 #include <linux/mutex.h>		/* struct mutex */
 #include <linux/rwsem.h>		/* struct rw_semaphore */
 #include <linux/pm.h>			/* pm_message_t */
+#include <linux/device.h>
 
 /* forward declarations */
 #ifdef CONFIG_PCI
@@ -186,6 +187,7 @@ struct snd_minor {
 	int device;			/* device number */
 	const struct file_operations *f_ops;	/* file operations */
 	void *private_data;		/* private data for f_ops->open */
+	struct class_device *class_dev;	/* class device for sysfs */
 };
 
 /* sound.c */
@@ -200,6 +202,8 @@ int snd_register_device(int type, struct snd_card *card, int dev,
 			const char *name);
 int snd_unregister_device(int type, struct snd_card *card, int dev);
 void *snd_lookup_minor_data(unsigned int minor, int type);
+int snd_add_device_sysfs_file(int type, struct snd_card *card, int dev,
+			      const struct class_device_attribute *attr);
 
 #ifdef CONFIG_SND_OSSEMUL
 int snd_register_oss_device(int type, struct snd_card *card, int dev,

sound/core/pcm.c

@@ -907,6 +907,28 @@ void snd_pcm_detach_substream(struct snd_pcm_substream *substream)
 	substream->pstr->substream_opened--;
 }
 
+static ssize_t show_pcm_class(struct class_device *class_device, char *buf)
+{
+	struct snd_pcm *pcm;
+	const char *str;
+	static const char *strs[SNDRV_PCM_CLASS_LAST + 1] = {
+		[SNDRV_PCM_CLASS_GENERIC] = "generic",
+		[SNDRV_PCM_CLASS_MULTI] = "multi",
+		[SNDRV_PCM_CLASS_MODEM] = "modem",
+		[SNDRV_PCM_CLASS_DIGITIZER] = "digitizer",
+	};
+
+	if (! (pcm = class_get_devdata(class_device)) ||
+	    pcm->dev_class > SNDRV_PCM_CLASS_LAST)
+		str = "none";
+	else
+		str = strs[pcm->dev_class];
+        return snprintf(buf, PAGE_SIZE, "%s\n", str);
+}
+
+static struct class_device_attribute pcm_attrs =
+	__ATTR(pcm_class, S_IRUGO, show_pcm_class, NULL);
+
 static int snd_pcm_dev_register(struct snd_device *device)
 {
 	int cidx, err;
@@ -945,6 +967,8 @@ static int snd_pcm_dev_register(struct snd_device *device)
 			mutex_unlock(&register_mutex);
 			return err;
 		}
+		snd_add_device_sysfs_file(devtype, pcm->card, pcm->device,
+					  &pcm_attrs);
 		for (substream = pcm->streams[cidx].substream; substream; substream = substream->next)
 			snd_pcm_timer_init(substream);
 	}

sound/core/sound.c

@@ -268,7 +268,11 @@ int snd_register_device(int type, struct snd_card *card, int dev,
 	snd_minors[minor] = preg;
 	if (card)
 		device = card->dev;
-	class_device_create(sound_class, NULL, MKDEV(major, minor), device, "%s", name);
+	preg->class_dev = class_device_create(sound_class, NULL,
+					      MKDEV(major, minor),
+					      device, "%s", name);
+	if (preg->class_dev)
+		class_set_devdata(preg->class_dev, private_data);
 
 	mutex_unlock(&sound_mutex);
 	return 0;
@@ -276,6 +280,24 @@ int snd_register_device(int type, struct snd_card *card, int dev,
 
 EXPORT_SYMBOL(snd_register_device);
 
+/* find the matching minor record
+ * return the index of snd_minor, or -1 if not found
+ */
+static int find_snd_minor(int type, struct snd_card *card, int dev)
+{
+	int cardnum, minor;
+	struct snd_minor *mptr;
+
+	cardnum = card ? card->number : -1;
+	for (minor = 0; minor < ARRAY_SIZE(snd_minors); ++minor)
+		if ((mptr = snd_minors[minor]) != NULL &&
+		    mptr->type == type &&
+		    mptr->card == cardnum &&
+		    mptr->device == dev)
+			return minor;
+	return -1;
+}
+
 /**
  * snd_unregister_device - unregister the device on the given card
  * @type: the device type, SNDRV_DEVICE_TYPE_XXX
@@ -289,32 +311,42 @@ EXPORT_SYMBOL(snd_register_device);
  */
 int snd_unregister_device(int type, struct snd_card *card, int dev)
 {
-	int cardnum, minor;
-	struct snd_minor *mptr;
+	int minor;
 
-	cardnum = card ? card->number : -1;
 	mutex_lock(&sound_mutex);
-	for (minor = 0; minor < ARRAY_SIZE(snd_minors); ++minor)
-		if ((mptr = snd_minors[minor]) != NULL &&
-		    mptr->type == type &&
-		    mptr->card == cardnum &&
-		    mptr->device == dev)
-			break;
-	if (minor == ARRAY_SIZE(snd_minors)) {
+	minor = find_snd_minor(type, card, dev);
+	if (minor < 0) {
 		mutex_unlock(&sound_mutex);
 		return -EINVAL;
 	}
 
 	class_device_destroy(sound_class, MKDEV(major, minor));
 
+	kfree(snd_minors[minor]);
 	snd_minors[minor] = NULL;
 	mutex_unlock(&sound_mutex);
-	kfree(mptr);
 	return 0;
 }
 
 EXPORT_SYMBOL(snd_unregister_device);
 
+int snd_add_device_sysfs_file(int type, struct snd_card *card, int dev,
+			      const struct class_device_attribute *attr)
+{
+	int minor, ret = -EINVAL;
+	struct class_device *cdev;
+
+	mutex_lock(&sound_mutex);
+	minor = find_snd_minor(type, card, dev);
+	if (minor >= 0 && (cdev = snd_minors[minor]->class_dev) != NULL)
+		ret = class_device_create_file(cdev, attr);
+	mutex_unlock(&sound_mutex);
+	return ret;
+
+}
+
+EXPORT_SYMBOL(snd_add_device_sysfs_file);
+
 #ifdef CONFIG_PROC_FS
 /*
  *  INFO PART