Messages in this thread | | | Subject | Re: [PATCH] mtd: allow mtd and jffs2 when ARCH=um | From | Artem Bityutskiy <> | Date | Tue, 14 Dec 2010 18:24:38 +0200 |
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On Tue, 2010-12-07 at 10:20 -0800, Jason Lunz wrote: > On Tue, Dec 07, 2010 at 10:39:41AM +0100, richard -rw- weinberger wrote: > > On Tue, Dec 7, 2010 at 8:29 AM, Jason Lunz <lunz@acm.org> wrote: > > > > > > Allow parts of drivers/mtd to compile on uml by pushing the HAS_IOMEM > > > dependencies down closer to the parts of mtd that actually need it. > > > This allows enough of mtd to build to let jffs2 be used on uml. > > > > > > Signed-off-by: Jason Lunz <lunz@acm.org> > > > --- > > > arch/um/Kconfig.rest | 4 +--- > > > drivers/mtd/Kconfig | 1 - > > > drivers/mtd/Makefile | 3 ++- > > > drivers/mtd/chips/Kconfig | 4 ++++ > > > drivers/mtd/devices/Kconfig | 8 ++++++++ > > > drivers/mtd/maps/Kconfig | 4 ++++ > > > drivers/mtd/mtdchar.c | 4 ++++ > > > drivers/mtd/nand/Kconfig | 3 +++ > > > drivers/mtd/onenand/Kconfig | 3 +++ > > > include/linux/mtd/map.h | 2 ++ > > > 10 files changed, 31 insertions(+), 5 deletions(-) > > > > > > diff --git a/arch/um/Kconfig.rest b/arch/um/Kconfig.rest > > > index 0ccad0f..e34f399 100644 > > > --- a/arch/um/Kconfig.rest > > > +++ b/arch/um/Kconfig.rest > > > @@ -28,9 +28,7 @@ source "drivers/scsi/Kconfig" > > > > > > source "drivers/md/Kconfig" > > > > > > -if BROKEN > > > - source "drivers/mtd/Kconfig" > > > -endif > > > +source "drivers/mtd/Kconfig" > > > > drivers/mtd was already marked as broken when we moved over to git (2.6.12-rc2). > > > > Do you exactly know why it was marked and fixes this patch all issues? > > I don't know exactly why it was originally marked BROKEN. I imagine it > was because most of the low-level mtd drivers need readb/writeb and > friends, which don't exist on uml. But now that mtd has virtual ram- and > blockdev-backed drivers, that's no longer sufficient reason to omit the > whole subsystem. > > I can't claim that this fixes all possible issues of course, but I've > privately been using this patch to run block2mtd under uml for years. My > original motivation was to allow the use of jffs2 in a uml-based test > environment and for that it's worked very well.
But I think your solution is a bit dirty, because it adds a great deal of little 'if HAS_IOMEM' and '#ifdef CONFIG_HAS_IOMEM' to many places. This is error-prone.
Instead, you should solve this problem in UML code. I do not know how, but may be you can add readb/writeb there which actually do nothing or print a scary warning, or do BUG(), and let things which use them just fail run-time.
Anyway, please, think about a solution which needs few changes in UML code instead of myriads of small little changes in many places.
Thanks!
-- Best Regards, Artem Bityutskiy (Артём Битюцкий)
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