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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>
This commit is contained in:
Olof Johansson 2010-09-17 21:19:57 -04:00 committed by Chris Ball
parent 061c6c847e
commit 5e71b7a64c
3 changed files with 56 additions and 14 deletions
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6
Documentation/devices.txt
View File

@ -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

17
drivers/mmc/card/Kconfig
View File

@ -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

47
drivers/mmc/card/block.c
View File

@ -43,15 +43,27 @@
#include "queue.h"
MODULE_ALIAS("mmc:block");
/*
* max 8 partitions per card
*/
#define MMC_SHIFT 3
#define MMC_NUM_MINORS (256 >> MMC_SHIFT)
#ifdef MODULE_PARAM_PREFIX
#undef MODULE_PARAM_PREFIX
#endif
#define MODULE_PARAM_PREFIX "mmcblk."
static DEFINE_MUTEX(block_mutex);
static DECLARE_BITMAP(dev_use, MMC_NUM_MINORS);
/*
* The defaults come from config options but can be overriden by module
* or bootarg options.
*/
static int perdev_minors = CONFIG_MMC_BLOCK_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;