mmc: make number of mmcblk minors configurable

The old limit of number of minor numbers per mmcblk device was hardcoded at 8. This isn't enough for some of the more elaborate partitioning schemes, for example those used by Chrome OS. Since there might be a bunch of systems out there with static /dev contents that relies on the old numbering scheme, let's make it a build-time option with the default set to the previous 8. Also provide a boot/modprobe-time parameter to override the config default: mmcblk.perdev_minors. Signed-off-by: Olof Johansson <olof@lixom.net> Cc: Mandeep Baines <msb@chromium.org> Cc: <linux-mmc@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Chris Ball <cjb@laptop.org>

mmc: make number of mmcblk minors configurable
The old limit of number of minor numbers per mmcblk device was hardcoded at 8. This isn't enough for some of the more elaborate partitioning schemes, for example those used by Chrome OS. Since there might be a bunch of systems out there with static /dev contents that relies on the old numbering scheme, let's make it a build-time option with the default set to the previous 8. Also provide a boot/modprobe-time parameter to override the config default: mmcblk.perdev_minors. Signed-off-by: Olof Johansson <olof@lixom.net> Cc: Mandeep Baines <msb@chromium.org> Cc: <linux-mmc@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Chris Ball <cjb@laptop.org>
Olof Johansson · Chris Ball
1 parent 061c6c847e
Showing 3 changed files with 54 additions and 12 deletions Side-by-side Diff
Documentation/devices.txt
drivers/mmc/card/Kconfig
drivers/mmc/card/block.c
@@ -2520,6 +2520,12 @@
 		  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
@@ -14,6 +14,23 @@
 	  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
@@ -43,16 +43,28 @@
 #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 @@
  
 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 @@
 	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 @@
 	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 @@
 	 */
 	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 @@
 	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 @@
 {
 	struct mmc_blk_data *md;
 	int err;
-
 	char cap_str[10];
  
 	/*
@@ -759,6 +773,11 @@
 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)
...	...	@@ -2520,6 +2520,12 @@
2520	2520	8 = /dev/mmcblk1 Second SD/MMC card
2521	2521	...
2522	2522
	2523	+ The start of next SD/MMC card can be configured with
	2524	+ CONFIG_MMC_BLOCK_MINORS, or overridden at boot/modprobe
	2525	+ time using the mmcblk.perdev_minors option. That would
	2526	+ bump the offset between each card to be the configured
	2527	+ value instead of the default 8.
	2528	+
2523	2529	179 char CCube DVXChip-based PCI products
2524	2530	0 = /dev/dvxirq0 First DVX device
2525	2531	1 = /dev/dvxirq1 Second DVX device
...	...	@@ -14,6 +14,23 @@
14	14	mount the filesystem. Almost everyone wishing MMC support
15	15	should say Y or M here.
16	16
	17	+config MMC_BLOCK_MINORS
	18	+ int "Number of minors per block device"
	19	+ range 4 256
	20	+ default 8
	21	+ help
	22	+ Number of minors per block device. One is needed for every
	23	+ partition on the disk (plus one for the whole disk).
	24	+
	25	+ Number of total MMC minors available is 256, so your number
	26	+ of supported block devices will be limited to 256 divided
	27	+ by this number.
	28	+
	29	+ Default is 8 to be backwards compatible with previous
	30	+ hardwired device numbering.
	31	+
	32	+ If unsure, say 8 here.
	33	+
17	34	config MMC_BLOCK_BOUNCE
18	35	bool "Use bounce buffer for simple hosts"
19	36	depends on MMC_BLOCK
...	...	@@ -43,16 +43,28 @@
43	43	#include "queue.h"
44	44
45	45	MODULE_ALIAS("mmc:block");
	46	+#ifdef MODULE_PARAM_PREFIX
	47	+#undef MODULE_PARAM_PREFIX
	48	+#endif
	49	+#define MODULE_PARAM_PREFIX "mmcblk."
46	50
	51	+static DEFINE_MUTEX(block_mutex);
	52	+
47	53	/*
48		- * max 8 partitions per card
	54	+ * The defaults come from config options but can be overriden by module
	55	+ * or bootarg options.
49	56	*/
50		-#define MMC_SHIFT 3
51		-#define MMC_NUM_MINORS (256 >> MMC_SHIFT)
	57	+static int perdev_minors = CONFIG_MMC_BLOCK_MINORS;
52	58
53		-static DEFINE_MUTEX(block_mutex);
54		-static DECLARE_BITMAP(dev_use, MMC_NUM_MINORS);
	59	+/*
	60	+ * We've only got one major, so number of mmcblk devices is
	61	+ * limited to 256 / number of minors per device.
	62	+ */
	63	+static int max_devices;
55	64
	65	+/* 256 minors, so at most 256 separate devices */
	66	+static DECLARE_BITMAP(dev_use, 256);
	67	+
56	68	/*
57	69	* There is one mmc_blk_data per slot.
58	70	*/
...	...	@@ -67,6 +79,9 @@
67	79
68	80	static DEFINE_MUTEX(open_lock);
69	81
	82	+module_param(perdev_minors, int, 0444);
	83	+MODULE_PARM_DESC(perdev_minors, "Minors numbers to allocate per device");
	84	+
70	85	static struct mmc_blk_data mmc_blk_get(struct gendisk disk)
71	86	{
72	87	struct mmc_blk_data *md;
73	88
...	...	@@ -88,10 +103,10 @@
88	103	md->usage--;
89	104	if (md->usage == 0) {
90	105	int devmaj = MAJOR(disk_devt(md->disk));
91		- int devidx = MINOR(disk_devt(md->disk)) >> MMC_SHIFT;
	106	+ int devidx = MINOR(disk_devt(md->disk)) / perdev_minors;
92	107
93	108	if (!devmaj)
94		- devidx = md->disk->first_minor >> MMC_SHIFT;
	109	+ devidx = md->disk->first_minor / perdev_minors;
95	110
96	111	blk_cleanup_queue(md->queue.queue);
97	112
...	...	@@ -566,8 +581,8 @@
566	581	struct mmc_blk_data *md;
567	582	int devidx, ret;
568	583
569		- devidx = find_first_zero_bit(dev_use, MMC_NUM_MINORS);
570		- if (devidx >= MMC_NUM_MINORS)
	584	+ devidx = find_first_zero_bit(dev_use, max_devices);
	585	+ if (devidx >= max_devices)
571	586	return ERR_PTR(-ENOSPC);
572	587	__set_bit(devidx, dev_use);
573	588
...	...	@@ -584,7 +599,7 @@
584	599	*/
585	600	md->read_only = mmc_blk_readonly(card);
586	601
587		- md->disk = alloc_disk(1 << MMC_SHIFT);
	602	+ md->disk = alloc_disk(perdev_minors);
588	603	if (md->disk == NULL) {
589	604	ret = -ENOMEM;
590	605	goto err_kfree;
...	...	@@ -601,7 +616,7 @@
601	616	md->queue.data = md;
602	617
603	618	md->disk->major = MMC_BLOCK_MAJOR;
604		- md->disk->first_minor = devidx << MMC_SHIFT;
	619	+ md->disk->first_minor = devidx * perdev_minors;
605	620	md->disk->fops = &mmc_bdops;
606	621	md->disk->private_data = md;
607	622	md->disk->queue = md->queue.queue;
...	...	@@ -670,7 +685,6 @@
670	685	{
671	686	struct mmc_blk_data *md;
672	687	int err;
673		-
674	688	char cap_str[10];
675	689
676	690	/*
...	...	@@ -759,6 +773,11 @@
759	773	static int __init mmc_blk_init(void)
760	774	{
761	775	int res;
	776	+
	777	+ if (perdev_minors != CONFIG_MMC_BLOCK_MINORS)
	778	+ pr_info("mmcblk: using %d minors per device\n", perdev_minors);
	779	+
	780	+ max_devices = 256 / perdev_minors;
762	781
763	782	res = register_blkdev(MMC_BLOCK_MAJOR, "mmc");
764	783	if (res)