Re: Two questions on mtds on x86 platform - multiple mtdram

[MikeW <mw_phil@yahoo.co.uk>]

David Woodhouse <dwmw2 <at> infradead.org> writes:

> 
> On Thu, 2003-02-06 at 14:43, Somashekara DM wrote:
> > Hi,
> > 
> > We want to mount jffs2 on two mtd partitions as a part of our project.
> > Our platform is x86 - kernel version 2.4.13.
> > 
> > 1. We are using mtdram ("Test driver using RAM") and blkmtd ("MTD
> > emulation using block device")
> >     to create two mtd's. Our aim is to mount jffs2 on two different
> > mtds.
> 
> OK. So you have two MTD devices listed in /proc/mtd?
> 
> > Here are the steps we have followed.
> > 
> > Step1 :
> >     mknod /dev/mtd0 c 90 0
> >     mknod /dev/mtd2 c 90 2
> 
> This is incorrect. The MAKEDEV script in CVS is correct. The device
> numbers for the character devices alternate between 'normal' and
> read-only devices, as follows:
> 
> 	/dev/mtd0	c 90 0
> 	/dev/mtdr0	c 90 1
> 	/dev/mtd1	c 90 2
> 	/dev/mtdr1	c 90 3
> 	/dev/mtd2	c 90 4
> 	/dev/mtdr2	c 90 5
> 
> So what you've called '/dev/mtd2' is in fact what _should_ be called
> '/dev/mtd1', and is hence the second of the two MTD devices (In fact, 
> /dev/mtd2 would be a _third_ device, which does not exist in your
> system).
> 
> >     and
> >     mknod /dev/mtdblock0 b 31 0
> >     mknod /dev/mtdblock2 b 31 2
> 
> These are correct device numbers and names but as before, /dev/mtdblock2
> refers to a third MTD device which does not exist in your system. Make
> /dev/mtdblock1 (b 31 1) and use that.
> 
> >    mount -t jffs2 /dev/mtdblock2 /mnt/jffs2drive2    //this mount fails
> >    error - "mount: fs type jffs2 not supported by kernel"
> 
> What it actually means is 'block device /dev/mtdblock2 does not exist'.
> But mount(2) doesn't return sensible errors.
> 
> > 2. Can we create multiple partitions on the 'mtdram'?
> >        Can you give us the procedure for that?
> 
> No partitions, but you can load the mtdram module twice (with different
> names) so that you get two devices.
> 

Does this mean that in order to create several mtd devices on mtdram,
I can just create several device nodes with different minor device numbers ?

If so, I presume this means that all devices must share the same
size and erasesize ?


Regards,
Mike

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