mtd: Replace static array of devices with an idr structure

Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdcore.c

@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/mtd/compatmac.h>
 #include <linux/proc_fs.h>
+#include <linux/idr.h>
 
 #include <linux/mtd/mtd.h>
 #include "internal.h"
@@ -33,13 +34,18 @@ static struct class mtd_class = {
 	.resume = mtd_cls_resume,
 };
 
+static DEFINE_IDR(mtd_idr);
+
 /* These are exported solely for the purpose of mtd_blkdevs.c. You
    should not use them for _anything_ else */
 DEFINE_MUTEX(mtd_table_mutex);
-struct mtd_info *mtd_table[MAX_MTD_DEVICES];
-
 EXPORT_SYMBOL_GPL(mtd_table_mutex);
-EXPORT_SYMBOL_GPL(mtd_table);
+
+struct mtd_info *__mtd_next_device(int i)
+{
+	return idr_get_next(&mtd_idr, &i);
+}
+EXPORT_SYMBOL_GPL(__mtd_next_device);
 
 static LIST_HEAD(mtd_notifiers);
 
@@ -235,13 +241,13 @@ static struct device_type mtd_devtype = {
  *	Add a device to the list of MTD devices present in the system, and
  *	notify each currently active MTD 'user' of its arrival. Returns
  *	zero on success or 1 on failure, which currently will only happen
- *	if the number of present devices exceeds MAX_MTD_DEVICES (i.e. 16)
- *	or there's a sysfs error.
+ *	if there is insufficient memory or a sysfs error.
  */
 
 int add_mtd_device(struct mtd_info *mtd)
 {
-	int i;
+	struct mtd_notifier *not;
+	int i, error;
 
 	if (!mtd->backing_dev_info) {
 		switch (mtd->type) {
@@ -260,11 +266,15 @@ int add_mtd_device(struct mtd_info *mtd)
 	BUG_ON(mtd->writesize == 0);
 	mutex_lock(&mtd_table_mutex);
 
-	for (i=0; i < MAX_MTD_DEVICES; i++)
-		if (!mtd_table[i]) {
-			struct mtd_notifier *not;
+	do {
+		if (!idr_pre_get(&mtd_idr, GFP_KERNEL))
+			goto fail_locked;
+		error = idr_get_new(&mtd_idr, mtd, &i);
+	} while (error == -EAGAIN);
+
+	if (error)
+		goto fail_locked;
 
-			mtd_table[i] = mtd;
 	mtd->index = i;
 	mtd->usecount = 0;
 
@@ -286,8 +296,7 @@ int add_mtd_device(struct mtd_info *mtd)
 	    && (mtd->flags & MTD_POWERUP_LOCK) && mtd->unlock) {
 		if (mtd->unlock(mtd, 0, mtd->size))
 			printk(KERN_WARNING
-					       "%s: unlock failed, "
-					       "writes may not work\n",
+			       "%s: unlock failed, writes may not work\n",
 			       mtd->name);
 	}
 
@@ -299,17 +308,15 @@ int add_mtd_device(struct mtd_info *mtd)
 	mtd->dev.devt = MTD_DEVT(i);
 	dev_set_name(&mtd->dev, "mtd%d", i);
 	dev_set_drvdata(&mtd->dev, mtd);
-			if (device_register(&mtd->dev) != 0) {
-				mtd_table[i] = NULL;
-				break;
-			}
+	if (device_register(&mtd->dev) != 0)
+		goto fail_added;
 
 	if (MTD_DEVT(i))
 		device_create(&mtd_class, mtd->dev.parent,
 			      MTD_DEVT(i) + 1,
 			      NULL, "mtd%dro", i);
 
-			DEBUG(0, "mtd: Giving out device %d to %s\n",i, mtd->name);
+	DEBUG(0, "mtd: Giving out device %d to %s\n", i, mtd->name);
 	/* No need to get a refcount on the module containing
 	   the notifier, since we hold the mtd_table_mutex */
 	list_for_each_entry(not, &mtd_notifiers, list)
@@ -322,8 +329,10 @@ int add_mtd_device(struct mtd_info *mtd)
 	   either. :) */
 	__module_get(THIS_MODULE);
 	return 0;
-		}
 
+fail_added:
+	idr_remove(&mtd_idr, i);
+fail_locked:
 	mutex_unlock(&mtd_table_mutex);
 	return 1;
 }
@@ -344,7 +353,7 @@ int del_mtd_device (struct mtd_info *mtd)
 
 	mutex_lock(&mtd_table_mutex);
 
-	if (mtd_table[mtd->index] != mtd) {
+	if (idr_find(&mtd_idr, mtd->index) != mtd) {
 		ret = -ENODEV;
 	} else if (mtd->usecount) {
 		printk(KERN_NOTICE "Removing MTD device #%d (%s) with use count %d\n",
@@ -360,7 +369,7 @@ int del_mtd_device (struct mtd_info *mtd)
 		list_for_each_entry(not, &mtd_notifiers, list)
 			not->remove(mtd);
 
-		mtd_table[mtd->index] = NULL;
+		idr_remove(&mtd_idr, mtd->index);
 
 		module_put(THIS_MODULE);
 		ret = 0;
@@ -448,8 +457,8 @@ struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num)
 				break;
 			}
 		}
-	} else if (num >= 0 && num < MAX_MTD_DEVICES) {
-		ret = mtd_table[num];
+	} else if (num >= 0) {
+		ret = idr_find(&mtd_idr, num);
 		if (mtd && mtd != ret)
 			ret = NULL;
 	}

drivers/mtd/mtdcore.h

@@ -8,17 +8,7 @@
    should not use them for _anything_ else */
 
 extern struct mutex mtd_table_mutex;
-extern struct mtd_info *mtd_table[MAX_MTD_DEVICES];
-
-static inline struct mtd_info *__mtd_next_device(int i)
-{
-	while (i < MAX_MTD_DEVICES) {
-		if (mtd_table[i])
-			return mtd_table[i];
-		i++;
-	}
-	return NULL;
-}
+extern struct mtd_info *__mtd_next_device(int i);
 
 #define mtd_for_each_device(mtd)			\
 	for ((mtd) = __mtd_next_device(0);		\

include/linux/mtd/mtd.h

@@ -20,7 +20,6 @@
 
 #define MTD_CHAR_MAJOR 90
 #define MTD_BLOCK_MAJOR 31
-#define MAX_MTD_DEVICES 32
 
 #define MTD_ERASE_PENDING      	0x01
 #define MTD_ERASING		0x02