Re: [microblaze-uclinux] How To Read/Write To Flash Device

[Torin Ford <torin@xxxxxxxxxxxx>]

On Mon, 2009-09-07 at 09:21 +1000, John Williams wrote:
> Hi,
> 
> On Mon, Sep 7, 2009 at 8:20 AM, Torin Ford<torin@xxxxxxxxxxxx> wrote:
> > Hopefully a quick question here.  I'm assuming that /dev/mtdblock[0-n]
> > are the partitions that are defined under "Flash Partition Table" and
> > are setup as READ ONLY devices.  Does that then mean that /dev/mtd[0-n]
> > are the READ/WRITE devices for that same flash device?
> 
> Not quite - /dev/mtdN are character device iunterfaces to the flash
> partitions, while mtdblockN are block device interfaces.  So, if you
> want to mount a filesystem (other than JFFS2) on MTD, you use the
> block interface.
> 
> 
> > If this is true,
> > does anything special need to be done to correctly write to them?  I did
> > a read, then a write, and then another read.  What I wrote was not what
> > I read back on the second read, but it also wasn't what I read on the
> > first read.  So it apparently changed the bits on the device, but not to
> > what I was looking for.  btw, I believe the device I'm using is a
> > Spansion NOR chip.
> 
> The simplest sequence to test is something like:
> 
> $ eraseall /dev/mtdN
> $ cat /path/to/somefile > /dev/mtdD
> $ cat /dev/mtdN
> 
> You can then confirm that the data were corectly written.  Don't
> forget the eraseall command - you must clear the flash before you
> rewrite it.
> 
> Regards,
> 
> John

John,
   Thanks for the response.  I tried it out and it worked as expected.
I checked out the eraseall code and incorporated the ioctl call(s) into
my code to do the erase.  That's what he problem was.

Thanks,

Torin Ford
Software Engineer
nextScan, Inc.
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