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Message-ID: <20100820221323.GC8535@lixom.net>
Date: Fri, 20 Aug 2010 17:13:23 -0500
From: Olof Johansson <olof@...om.net>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
Mandeep Baines <msb@...omium.org>
Subject: [PATCH v3] mmc: add config and runtime option for number of mmcblk
minors
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@...om.net>
Cc: Mandeep Baines <msb@...omium.org>
---
Andrew, sorry for the churn but Mandeep had a couple of good points that
needed addressing.
Changes since v1:
* Runtime override of config default
* Better help text
* DIV_ROUND_UP for max_devices calculation
* Clarify mmcblk device count limitations
Changes since v2 based on feedback from Mandeep Baines:
* DIV_ROUND_UP is doing the wrong thing, we'll end up using
the last fractional range of minors which we shouldn't.
* Documentation/devices.txt update
* No need to compute max_devices twice, just do it at runtime.
* Permission fix for the module_param -- it's readonly.
Documentation/devices.txt | 6 ++++++
drivers/mmc/card/Kconfig | 17 +++++++++++++++++
drivers/mmc/card/block.c | 41 ++++++++++++++++++++++++++++++-----------
3 files changed, 53 insertions(+), 11 deletions(-)
diff --git a/Documentation/devices.txt b/Documentation/devices.txt
index 1d83d12..fdf3821 100644
--- a/Documentation/devices.txt
+++ b/Documentation/devices.txt
@@ -2518,6 +2518,12 @@ 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 3f2a912..57e4416 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 cb9fbc8..ec94f56 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -43,14 +43,26 @@
#include "queue.h"
MODULE_ALIAS("mmc:block");
+#ifdef MODULE_PARAM_PREFIX
+#undef MODULE_PARAM_PREFIX
+#endif
+#define MODULE_PARAM_PREFIX "mmcblk."
+
+
+/*
+ * The defaults come from config options but can be overriden by module
+ * or bootarg options.
+ */
+static int perdev_minors = CONFIG_MMC_BLOCK_MINORS;
/*
- * max 8 partitions per card
+ * We've only got one major, so number of mmcblk devices is
+ * limited to 256 / number of minors per device.
*/
-#define MMC_SHIFT 3
-#define MMC_NUM_MINORS (256 >> MMC_SHIFT)
+static int max_devices;
-static DECLARE_BITMAP(dev_use, MMC_NUM_MINORS);
+/* 256 minors, so at most 256 separate devices */
+static DECLARE_BITMAP(dev_use, 256);
/*
* There is one mmc_blk_data per slot.
@@ -66,6 +78,9 @@ 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;
@@ -87,10 +102,10 @@ 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);
@@ -482,8 +497,8 @@ 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);
@@ -500,7 +515,7 @@ 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;
@@ -517,7 +532,7 @@ 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;
@@ -593,7 +608,6 @@ static int mmc_blk_probe(struct mmc_card *card)
{
struct mmc_blk_data *md;
int err;
-
char cap_str[10];
/*
@@ -683,6 +697,11 @@ 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;
--
1.5.6.5
--
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