3 files changed, 54 insertions, 12 deletions

diff --git a/Documentation/devices.txt b/Documentation/devices.txt
index c58abf1ccc71..170cc1e7e135 100644
--- a/Documentation/devices.txt
+++ b/Documentation/devices.txt
@@ -2520,6 +2520,12 @@ Your cooperation is appreciated.
                   8 = /dev/mmcblk1      Second SD/MMC card
                     ...
 
+                The start of next SD/MMC card can be configured with
+                CONFIG_MMC_BLOCK_MINORS, or overridden at boot/modprobe
+                time using the mmcblk.perdev_minors option. That would
+                bump the offset between each card to be the configured
+                value instead of the default 8.
+
 179 char        CCube DVXChip-based PCI products
                   0 = /dev/dvxirq0      First DVX device
                   1 = /dev/dvxirq1      Second DVX device
diff --git a/drivers/mmc/card/Kconfig b/drivers/mmc/card/Kconfig
index 3f2a912659af..57e4416b9ef0 100644
--- a/drivers/mmc/card/Kconfig
+++ b/drivers/mmc/card/Kconfig
@@ -14,6 +14,23 @@ config MMC_BLOCK
           mount the filesystem. Almost everyone wishing MMC support
           should say Y or M here.
 
+config MMC_BLOCK_MINORS
+        int "Number of minors per block device"
+        range 4 256
+        default 8
+        help
+          Number of minors per block device. One is needed for every
+          partition on the disk (plus one for the whole disk).
+
+          Number of total MMC minors available is 256, so your number
+          of supported block devices will be limited to 256 divided
+          by this number.
+
+          Default is 8 to be backwards compatible with previous
+          hardwired device numbering.
+
+          If unsure, say 8 here.
+
 config MMC_BLOCK_BOUNCE
         bool "Use bounce buffer for simple hosts"
         depends on MMC_BLOCK
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index a9970504cabb..217f82037fc1 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -43,15 +43,27 @@
 #include "queue.h"
 
 MODULE_ALIAS("mmc:block");
+#ifdef MODULE_PARAM_PREFIX
+#undef MODULE_PARAM_PREFIX
+#endif
+#define MODULE_PARAM_PREFIX "mmcblk."
+
+static DEFINE_MUTEX(block_mutex);
 
 /*
- * max 8 partitions per card
+ * The defaults come from config options but can be overriden by module
+ * or bootarg options.
  */
-#define MMC_SHIFT       3
-#define MMC_NUM_MINORS  (256 >> MMC_SHIFT)
+static int perdev_minors = CONFIG_MMC_BLOCK_MINORS;
 
-static DEFINE_MUTEX(block_mutex);
-static DECLARE_BITMAP(dev_use, MMC_NUM_MINORS);
+/*
+ * We've only got one major, so number of mmcblk devices is
+ * limited to 256 / number of minors per device.
+ */
+static int max_devices;
+
+/* 256 minors, so at most 256 separate devices */
+static DECLARE_BITMAP(dev_use, 256);
 
 /*
  * There is one mmc_blk_data per slot.
@@ -67,6 +79,9 @@ struct mmc_blk_data {
 
 static DEFINE_MUTEX(open_lock);
 
+module_param(perdev_minors, int, 0444);
+MODULE_PARM_DESC(perdev_minors, "Minors numbers to allocate per device");
+
 static struct mmc_blk_data *mmc_blk_get(struct gendisk *disk)
 {
         struct mmc_blk_data *md;
@@ -88,10 +103,10 @@ static void mmc_blk_put(struct mmc_blk_data *md)
         md->usage--;
         if (md->usage == 0) {
                 int devmaj = MAJOR(disk_devt(md->disk));
-                int devidx = MINOR(disk_devt(md->disk)) >> MMC_SHIFT;
+                int devidx = MINOR(disk_devt(md->disk)) / perdev_minors;
 
                 if (!devmaj)
-                        devidx = md->disk->first_minor >> MMC_SHIFT;
+                        devidx = md->disk->first_minor / perdev_minors;
 
                 blk_cleanup_queue(md->queue.queue);
 
@@ -566,8 +581,8 @@ static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card)
         struct mmc_blk_data *md;
         int devidx, ret;
 
-        devidx = find_first_zero_bit(dev_use, MMC_NUM_MINORS);
-        if (devidx >= MMC_NUM_MINORS)
+        devidx = find_first_zero_bit(dev_use, max_devices);
+        if (devidx >= max_devices)
                 return ERR_PTR(-ENOSPC);
         __set_bit(devidx, dev_use);
 
@@ -584,7 +599,7 @@ static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card)
          */
         md->read_only = mmc_blk_readonly(card);
 
-        md->disk = alloc_disk(1 << MMC_SHIFT);
+        md->disk = alloc_disk(perdev_minors);
         if (md->disk == NULL) {
                 ret = -ENOMEM;
                 goto err_kfree;
@@ -601,7 +616,7 @@ static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card)
         md->queue.data = md;
 
         md->disk->major = MMC_BLOCK_MAJOR;
-        md->disk->first_minor = devidx << MMC_SHIFT;
+        md->disk->first_minor = devidx * perdev_minors;
         md->disk->fops = &mmc_bdops;
         md->disk->private_data = md;
         md->disk->queue = md->queue.queue;
@@ -670,7 +685,6 @@ static int mmc_blk_probe(struct mmc_card *card)
 {
         struct mmc_blk_data *md;
         int err;
-
         char cap_str[10];
 
         /*
@@ -760,6 +774,11 @@ static int __init mmc_blk_init(void)
 {
         int res;
 
+        if (perdev_minors != CONFIG_MMC_BLOCK_MINORS)
+                pr_info("mmcblk: using %d minors per device\n", perdev_minors);
+
+        max_devices = 256 / perdev_minors;
+
         res = register_blkdev(MMC_BLOCK_MAJOR, "mmc");
         if (res)
                 goto out;