mtd: Replace static array of devices with an idr structure

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

3 files changed, 81 insertions, 83 deletions

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 402d41723c3f..b3b98d1fffc3 100644
--- a/drivers/mtd/mtdcore.c
+++ b/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) {
@@ -260,70 +266,73 @@ 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;
-
-                        mtd_table[i] = mtd;
-                        mtd->index = i;
-                        mtd->usecount = 0;
-
-                        if (is_power_of_2(mtd->erasesize))
-                                mtd->erasesize_shift = ffs(mtd->erasesize) - 1;
-                        else
-                                mtd->erasesize_shift = 0;
-
-                        if (is_power_of_2(mtd->writesize))
-                                mtd->writesize_shift = ffs(mtd->writesize) - 1;
-                        else
-                                mtd->writesize_shift = 0;
-
-                        mtd->erasesize_mask = (1 << mtd->erasesize_shift) - 1;
-                        mtd->writesize_mask = (1 << mtd->writesize_shift) - 1;
-
-                        /* Some chips always power up locked. Unlock them now */
-                        if ((mtd->flags & MTD_WRITEABLE)
-                            && (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",
-                                               mtd->name);
-                        }
+        do {
+                if (!idr_pre_get(&mtd_idr, GFP_KERNEL))
+                        goto fail_locked;
+                error = idr_get_new(&mtd_idr, mtd, &i);
+        } while (error == -EAGAIN);
 
-                        /* Caller should have set dev.parent to match the
-                         * physical device.
-                         */
-                        mtd->dev.type = &mtd_devtype;
-                        mtd->dev.class = &mtd_class;
-                        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 (error)
+                goto fail_locked;
 
-                        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);
-                        /* 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)
-                                not->add(mtd);
-
-                        mutex_unlock(&mtd_table_mutex);
-                        /* We _know_ we aren't being removed, because
-                           our caller is still holding us here. So none
-                           of this try_ nonsense, and no bitching about it
-                           either. :) */
-                        __module_get(THIS_MODULE);
-                        return 0;
-                }
+        mtd->index = i;
+        mtd->usecount = 0;
+
+        if (is_power_of_2(mtd->erasesize))
+                mtd->erasesize_shift = ffs(mtd->erasesize) - 1;
+        else
+                mtd->erasesize_shift = 0;
+
+        if (is_power_of_2(mtd->writesize))
+                mtd->writesize_shift = ffs(mtd->writesize) - 1;
+        else
+                mtd->writesize_shift = 0;
+
+        mtd->erasesize_mask = (1 << mtd->erasesize_shift) - 1;
+        mtd->writesize_mask = (1 << mtd->writesize_shift) - 1;
+
+        /* Some chips always power up locked. Unlock them now */
+        if ((mtd->flags & MTD_WRITEABLE)
+            && (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",
+                               mtd->name);
+        }
+
+        /* Caller should have set dev.parent to match the
+         * physical device.
+         */
+        mtd->dev.type = &mtd_devtype;
+        mtd->dev.class = &mtd_class;
+        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)
+                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);
+        /* 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)
+                not->add(mtd);
+
+        mutex_unlock(&mtd_table_mutex);
+        /* We _know_ we aren't being removed, because
+           our caller is still holding us here. So none
+           of this try_ nonsense, and no bitching about it
+           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;
         }
diff --git a/drivers/mtd/mtdcore.h b/drivers/mtd/mtdcore.h
index e2f93a300738..6a64fdebc898 100644
--- a/drivers/mtd/mtdcore.h
+++ b/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);              \
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 0f32a9b6ff55..ba53ecca107c 100644
--- a/include/linux/mtd/mtd.h
+++ b/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