[MMC] Add MMC class devices

Create a mmc_host class to allow enumeration of MMC host controllers
even though they have no card(s) inserted.

Patch based on work by Pierre Ossman.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/mmc/mmc.c

@@ -796,17 +796,13 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 {
 	struct mmc_host *host;
 
-	host = kmalloc(sizeof(struct mmc_host) + extra, GFP_KERNEL);
+	host = mmc_alloc_host_sysfs(extra, dev);
 	if (host) {
-		memset(host, 0, sizeof(struct mmc_host) + extra);
-
 		spin_lock_init(&host->lock);
 		init_waitqueue_head(&host->wq);
 		INIT_LIST_HEAD(&host->cards);
 		INIT_WORK(&host->detect, mmc_rescan, host);
 
-		host->dev = dev;
-
 		/*
 		 * By default, hosts do not support SGIO or large requests.
 		 * They have to set these according to their abilities.
@@ -828,15 +824,15 @@ EXPORT_SYMBOL(mmc_alloc_host);
  */
 int mmc_add_host(struct mmc_host *host)
 {
-	static unsigned int host_num;
+	int ret;
 
-	snprintf(host->host_name, sizeof(host->host_name),
-		 "mmc%d", host_num++);
-
-	mmc_power_off(host);
-	mmc_detect_change(host);
+	ret = mmc_add_host_sysfs(host);
+	if (ret == 0) {
+		mmc_power_off(host);
+		mmc_detect_change(host);
+	}
 
-	return 0;
+	return ret;
 }
 
 EXPORT_SYMBOL(mmc_add_host);
@@ -859,6 +855,7 @@ void mmc_remove_host(struct mmc_host *host)
 	}
 
 	mmc_power_off(host);
+	mmc_remove_host_sysfs(host);
 }
 
 EXPORT_SYMBOL(mmc_remove_host);
@@ -872,7 +869,7 @@ EXPORT_SYMBOL(mmc_remove_host);
 void mmc_free_host(struct mmc_host *host)
 {
 	flush_scheduled_work();
-	kfree(host);
+	mmc_free_host_sysfs(host);
 }
 
 EXPORT_SYMBOL(mmc_free_host);

drivers/mmc/mmc.h

@@ -13,4 +13,9 @@
 void mmc_init_card(struct mmc_card *card, struct mmc_host *host);
 int mmc_register_card(struct mmc_card *card);
 void mmc_remove_card(struct mmc_card *card);
+
+struct mmc_host *mmc_alloc_host_sysfs(int extra, struct device *dev);
+int mmc_add_host_sysfs(struct mmc_host *host);
+void mmc_remove_host_sysfs(struct mmc_host *host);
+void mmc_free_host_sysfs(struct mmc_host *host);
 #endif

drivers/mmc/mmc_sysfs.c

@@ -20,6 +20,7 @@
 
 #define dev_to_mmc_card(d)	container_of(d, struct mmc_card, dev)
 #define to_mmc_driver(d)	container_of(d, struct mmc_driver, drv)
+#define cls_dev_to_mmc_host(d)	container_of(d, struct mmc_host, class_dev)
 
 #define MMC_ATTR(name, fmt, args...)					\
 static ssize_t mmc_##name##_show (struct device *dev, struct device_attribute *attr, char *buf)	\
@@ -224,13 +225,82 @@ void mmc_remove_card(struct mmc_card *card)
 }
 
 
+static void mmc_host_classdev_release(struct class_device *dev)
+{
+	struct mmc_host *host = cls_dev_to_mmc_host(dev);
+	kfree(host);
+}
+
+static struct class mmc_host_class = {
+	.name		= "mmc_host",
+	.release	= mmc_host_classdev_release,
+};
+
+/*
+ * Internal function. Allocate a new MMC host.
+ */
+struct mmc_host *mmc_alloc_host_sysfs(int extra, struct device *dev)
+{
+	struct mmc_host *host;
+
+	host = kmalloc(sizeof(struct mmc_host) + extra, GFP_KERNEL);
+	if (host) {
+		memset(host, 0, sizeof(struct mmc_host) + extra);
+
+		host->dev = dev;
+		host->class_dev.dev = host->dev;
+		host->class_dev.class = &mmc_host_class;
+		class_device_initialize(&host->class_dev);
+	}
+
+	return host;
+}
+
+/*
+ * Internal function. Register a new MMC host with the MMC class.
+ */
+int mmc_add_host_sysfs(struct mmc_host *host)
+{
+	static unsigned int host_num;
+
+	snprintf(host->host_name, sizeof(host->host_name),
+		 "mmc%d", host_num++);
+
+	strlcpy(host->class_dev.class_id, host->host_name, BUS_ID_SIZE);
+	return class_device_add(&host->class_dev);
+}
+
+/*
+ * Internal function. Unregister a MMC host with the MMC class.
+ */
+void mmc_remove_host_sysfs(struct mmc_host *host)
+{
+	class_device_del(&host->class_dev);
+}
+
+/*
+ * Internal function. Free a MMC host.
+ */
+void mmc_free_host_sysfs(struct mmc_host *host)
+{
+	class_device_put(&host->class_dev);
+}
+
+
 static int __init mmc_init(void)
 {
-	return bus_register(&mmc_bus_type);
+	int ret = bus_register(&mmc_bus_type);
+	if (ret == 0) {
+		ret = class_register(&mmc_host_class);
+		if (ret)
+			bus_unregister(&mmc_bus_type);
+	}
+	return ret;
 }
 
 static void __exit mmc_exit(void)
 {
+	class_unregister(&mmc_host_class);
 	bus_unregister(&mmc_bus_type);
 }
 

include/linux/mmc/host.h

@@ -63,6 +63,7 @@ struct device;
 
 struct mmc_host {
 	struct device		*dev;
+	struct class_device	class_dev;
 	struct mmc_host_ops	*ops;
 	unsigned int		f_min;
 	unsigned int		f_max;