NOR flash writing

NOR flash writing

[Antony Pavlov]

Hi All!

I have barebox running on a board with SPI flash chip.
I can write to the SPI flash chip using /dev/nor0 interface.
Before writing data to the /dev/nor0 device I have to erase it explicitly with 'erase /dev/nor0' command.

How I can write to /dev/nor0 in a more transparent way. E.g. if I want to update only several bytes
on /dev/nor0 then I use 'mw -d /dev/nor0 ...' command and barebox  automatically reads appropriate
flash sector into RAM, modify it, erase NOR flash device sector and write new sector content into NOR flash device.

-- 
Best regards,
  Antony Pavlov

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Re: NOR flash writing

[Sascha Hauer]

On Mon, Jul 28, 2014 at 06:28:14PM +0400, Antony Pavlov wrote:
> Hi All!
> 
> I have barebox running on a board with SPI flash chip.
> I can write to the SPI flash chip using /dev/nor0 interface.
> Before writing data to the /dev/nor0 device I have to erase it explicitly with 'erase /dev/nor0' command.
> 
> How I can write to /dev/nor0 in a more transparent way. E.g. if I want to update only several bytes
> on /dev/nor0 then I use 'mw -d /dev/nor0 ...' command and barebox  automatically reads appropriate
> flash sector into RAM, modify it, erase NOR flash device sector and write new sector content into NOR flash device.

There's no convenient way for this, you have to do it manually:

- read a block to a file using memcpy
- modify it using mw
- erase flash block
- copy back using memcpy

I can't think up a good API to combine this into a single command.
I mean for simple modifications some more intelligent read/modify/write
command would work, but normally if you have more than one modification
to do then you don't want to erase your flash with each modification.

Sascha

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