Re: [uml-devel] Loopback mounting jffs2 under UML?

[Rob Landley <rob@landley.net>]

On Tuesday 18 December 2007 13:29:11 Jeff Dike wrote:
> On Tue, Dec 18, 2007 at 12:45:23PM -0600, Rob Landley wrote:
> > There's a way to make a loopback device look like a flash device, letting
> > you loopback mount jffs2, but it involves recompiling the kerenel to add
> > support for it, and of course I went "User Mode Linux"...  Except
> > that UML disables  the flash menu entirely.
> >
> > Suggestions?
>
> I see this in menuconfig:
>
> Symbol: MTD [=n]
>    Prompt: Memory Technology Device (MTD) support
>      Defined at drivers/mtd/Kconfig:3
>      Depends on: BROKEN && HAS_IOMEM
>
> You could try removing the dependencies on BROKEN and HAS_IOMEM and
> see what happens...


Actually, in -rc4 (what I have lying around), the depends is just on HAS_IOMEM, and the include in arch/um/Kconfig is guarded by "if BROKEN".

Building it, I hit the same darn error I've been patching my way around for months:

>   CC      arch/um/kernel/smp.o
> In file included from include/asm/arch/tlb.h:9,
>                  from include/asm/tlb.h:4,
>                  from arch/um/kernel/smp.c:8:
> include/asm-generic/tlb.h: In function ‘tlb_flush_mmu’:
> include/asm-generic/tlb.h:76: error: implicit declaration of function
> ‘release_pages’ include/asm-generic/tlb.h: In function ‘tlb_remove_page’:
> include/asm-generic/tlb.h:105: error: implicit declaration of function
> ‘page_cache_release’ make[1]: *** [arch/um/kernel/smp.o] Error 1
> make: *** [arch/um/kernel] Error 2

Patch that, and then it breaks with:

>   CC      drivers/mtd/chips/chipreg.o
> In file included from drivers/mtd/chips/chipreg.c:13:
> include/linux/mtd/map.h: In function ‘inline_map_read’:
> include/linux/mtd/map.h:378: error: implicit declaration of function
> ‘__raw_readb’ include/linux/mtd/map.h:380: error: implicit declaration of
> function ‘__raw_readw’ include/linux/mtd/map.h:382: error: implicit
> declaration of function ‘__raw_readl’ include/linux/mtd/map.h:385: error:
> implicit declaration of function ‘__raw_readq’ include/linux/mtd/map.h:388:
> error: implicit declaration of function ‘memcpy_fromio’
> include/linux/mtd/map.h: In function ‘inline_map_write’:
> include/linux/mtd/map.h:406: error: implicit declaration of function
> ‘memcpy_toio’ make[3]: *** [drivers/mtd/chips/chipreg.o] Error 1
> make[2]: *** [drivers/mtd/chips] Error 2
> make[1]: *** [drivers/mtd] Error 2

All I enabled was CONFIG_MTD_BLOCK.

To reproduce what I did, yank these lines:

diff -ru linux-2.6.24-rc4/arch/um/Kconfig linux-temp/arch/um/Kconfig
--- linux-2.6.24-rc4/arch/um/Kconfig	2007-12-03 22:26:10.000000000 -0600
+++ linux-temp/arch/um/Kconfig	2007-12-18 15:28:49.000000000 -0600
@@ -280,9 +280,7 @@
 
 source "drivers/md/Kconfig"
 
-if BROKEN
 	source "drivers/mtd/Kconfig"
-endif
 
 #This is just to shut up some Kconfig warnings, so no prompt.
 config INPUT
diff -ru linux-2.6.24-rc4/arch/um/kernel/smp.c linux-temp/arch/um/kernel/smp.c
--- linux-2.6.24-rc4/arch/um/kernel/smp.c	2007-12-03 22:26:10.000000000 -0600
+++ linux-temp/arch/um/kernel/smp.c	2007-12-18 15:30:49.000000000 -0600
@@ -5,6 +5,7 @@
 
 #include "linux/percpu.h"
 #include "asm/pgalloc.h"
+#include "linux/pagemap.h"
 #include "asm/tlb.h"
 
 /* For some reason, mmu_gathers are referenced when CONFIG_SMP is off. */
diff -ru linux-2.6.24-rc4/drivers/mtd/Kconfig linux-temp/drivers/mtd/Kconfig
--- linux-2.6.24-rc4/drivers/mtd/Kconfig	2007-12-03 22:26:10.000000000 -0600
+++ linux-temp/drivers/mtd/Kconfig	2007-12-18 15:24:41.000000000 -0600
@@ -2,7 +2,6 @@
 
 menuconfig MTD
 	tristate "Memory Technology Device (MTD) support"
-	depends on HAS_IOMEM
 	help
 	  Memory Technology Devices are flash, RAM and similar chips, often
 	  used for solid state file systems on embedded devices. This option


And then configure and build like so:

cat > mini.conf << EOF
CONFIG_BINFMT_ELF=y
CONFIG_HOSTFS=y
CONFIG_BLK_DEV=y
CONFIG_BLK_DEV_LOOP=y
CONFIG_STDERR_CONSOLE=y
CONFIG_UNIX98_PTYS=y
CONFIG_EXT2_FS=y
CONFIG_MTD=y
CONFIG_MTD_BLOCK=y
EOF
make ARCH=um allnoconfig KCONFIG_ALLCONFIG=mini.conf
make ARCH=um

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.

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