Problems with r/w on mtdblock0

Ian Relativity at
Tue Dec 5 21:28:19 EST 2000

Well, that's how this started;

 >    bash# dd if=/dev/zero of=/dev/mtdblock0 bs=512 count=1 
 >    end_request: I/O error, dev 1f:00 (mtdblock), sector 0 
 >    dd: /dev/mtdblock0: Input/output error 
 >    1+0 records in 
 >    0+0 records out 
 >    bash# /bin/dd if=/dev/mtdblock0 of=/dev/null bs=512 count=1 
 >    end_request: I/O error, dev 1f:00 (mtdblock), sector 0 
 >    /bin/dd: /dev/mtdblock0: Input/output error 
 >    0+0 records in 
 >    0+0 records out 

.. and Ollie said ...

 >        The /dev/mtdblockN device the the "block device" node for MTD devices. 
 >  In the DoC case, it can only read/write data in 8KB block (the erase size). 
 >  You can not read/write 512B on itm it will get "cached" by the driver. If 
 >  you are playing with the IPL stuff, WRITE TO /dev/mtd0. 
... which then started a series of questions about whether or not its being cached
and I'm just rebooting too soon, if that's possible.  *BUT* .. as above .. I'm getting
errors to that device (that I didn't used to).

See my next message (I'm currently writing) re access level via /dev/mtd0 ...

.. but then all of this thread is irrelevant (to me) if I can get my BIOS warez onto
the chip at the right location (which it appears the doc_loadbios has done), but
I still don't get my BIOS app touched  ... so something still isn't sitting right ...
I'm doing testing at the moment ... there *shouldn't* be a driver error ... I'm
stickin' with the Wookie defence ... ;)

> However using /dev/mtdblock0 should produce the same result as if you wrote
> to a disk partition or a file.  The latest MTD block interface always erase
> the flash region it is going to write to.  Even for large erase sectors the
> code is backing the entire sector, patching the data to write into it and
> eventually rewriting the whole sector back.
> So doing
> 	dd if=some_file of=/dev/mtdblock0 bs=512 count=1
> or even
> 	cp foobar.fs /dev/mtdblock1
> should just work.  If it doesn't then there is a bug.  It actually works
> just fine with NOR flash devices.
> Nicolas

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