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SubjectRe: [PATCH] mtd: allow mtd and jffs2 when ARCH=um
On Wed, Dec 15, 2010 at 02:19, Jason Lunz <> wrote:
> On Tue, Dec 14, 2010 at 06:49:02PM -0600, Rob Landley wrote:
>> The problem is that jffs2 is a filesystem, and thus something people would
>> really like to be able to loopback mount, but it's hardwired to assume it's
>> only ever stored on a certain type of hardware, and thus requies incestuous
>> knowledge of the erase granularity of the flash layer in order to function.
> I assume you can turn your jffs2 image file into a block dev using
> losetup, then turn the corresponding loop device into an mtd device
> using block2mtd, at which point you ought to be able to mount it with
> jffs2. I've never tried it.

And block2mtd is part of mtd, so you have to get mtd compiled first.

BTW, the patch I used in the past was less intrusive than yours.
I attached it, as I can't send it inline from here.
Note that it was against 2.6.31-rc4.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 --

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
commit 57fce0f17f497583266a26328690f40f33af08c5
Author: Geert Uytterhoeven <>
Date: Mon Dec 15 15:21:15 2008 +0100

UML: Enable MTD, by moving the dependency on HAS_IOMEM

Signed-off-by: Geert Uytterhoeven <>

diff --git a/arch/um/ b/arch/um/
index 0ccad0f..e34f399 100644
--- a/arch/um/
+++ b/arch/um/
@@ -28,9 +28,7 @@ source "drivers/scsi/Kconfig"

source "drivers/md/Kconfig"

- source "drivers/mtd/Kconfig"
+source "drivers/mtd/Kconfig"

source "drivers/leds/Kconfig"

diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
index b8e35a0..052b00c 100644
--- a/drivers/mtd/Kconfig
+++ b/drivers/mtd/Kconfig
@@ -1,6 +1,5 @@
menuconfig MTD
tristate "Memory Technology Device (MTD) support"
- depends on HAS_IOMEM
Memory Technology Devices are flash, RAM and similar chips, often
used for solid state file systems on embedded devices. This option
@@ -315,15 +314,17 @@ config MTD_OOPS
To use, add console=ttyMTDx to the kernel command line,
where x is the MTD device number to use.

-source "drivers/mtd/chips/Kconfig"
-source "drivers/mtd/maps/Kconfig"
+ source "drivers/mtd/chips/Kconfig"
+ source "drivers/mtd/maps/Kconfig"

source "drivers/mtd/devices/Kconfig"

-source "drivers/mtd/nand/Kconfig"
-source "drivers/mtd/onenand/Kconfig"
+ source "drivers/mtd/nand/Kconfig"
+ source "drivers/mtd/onenand/Kconfig"

source "drivers/mtd/lpddr/Kconfig"

diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
index 82d1e4d..09fb548 100644
--- a/drivers/mtd/Makefile
+++ b/drivers/mtd/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_MTD_OOPS) += mtdoops.o
nftl-objs := nftlcore.o nftlmount.o
inftl-objs := inftlcore.o inftlmount.o

-obj-y += chips/ lpddr/ maps/ devices/ nand/ onenand/ tests/
+obj-y += devices/ tests/

+obj-$(CONFIG_HAS_IOMEM) += chips/ lpddr/ maps/ nand/ onenand/
obj-$(CONFIG_MTD_UBI) += ubi/
diff --git a/drivers/mtd/devices/Kconfig b/drivers/mtd/devices/Kconfig
index 325fab9..88937d6 100644
--- a/drivers/mtd/devices/Kconfig
+++ b/drivers/mtd/devices/Kconfig
@@ -106,6 +106,7 @@ config M25PXX_USE_FAST_READ

config MTD_SLRAM
tristate "Uncached system RAM"
+ depends on HAS_IOMEM
If your CPU cannot cache all of the physical memory in your machine,
you can still use it for storage or swap by using this driver to
@@ -113,6 +114,7 @@ config MTD_SLRAM

config MTD_PHRAM
tristate "Physical system RAM"
+ depends on HAS_IOMEM
This is a re-implementation of the slram driver above.

@@ -179,6 +181,7 @@ config MTD_BLOCK2MTD
Testing MTD users (eg JFFS2) on large media and media that might
be removed during a write (using the floppy drive).

comment "Disk-On-Chip Device Drivers"

config MTD_DOC2000
@@ -297,5 +300,6 @@ config MTD_DOCPROBE_55AA
LinuxBIOS or if you need to recover a DiskOnChip Millennium on which
you have managed to wipe the first block.

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