Re: how little do i have to do to define flash layout on my system?

[Cliff Brake <cliff.brake@gmail.com>]

On Apr 10, 2005 4:41 PM, Robert P. J. Day <rpjday@mindspring.com> wrote:
> 
>   currently, my 8xx 2.4 kernel-based system defines its flash layout
> with a proprietary driver file we installed into the "maps" directory,
> but i'd like to simplify that approach.
> 
>   certainly, i can use command-line partitioning to define all of the
> partitions, making the driver file *way* simpler.  can i somehow avoid
> even the creation of that driver file (so i don't have to mess with
> the kernel source tree at all)?
> 
>   i just read that there is a generic driver for accessing CFI flash
> chips on systems that have no specific mapping driver.  does this mean
> what i think it means?  that i can somehow take advantage of that
> generic driver to avoid having to write my own?

I am using the MTD mechanism for defining the physical area where the
flash lives on several PXA systems:

CONFIG_MTD_PHYSMAP=y
CONFIG_MTD_PHYSMAP_START=0x0
CONFIG_MTD_PHYSMAP_LEN=0x4000000
CONFIG_MTD_PHYSMAP_BANKWIDTH=4

You can then use the kernel command line to define the partitions:

mtdparts=phys_mapped_flash:256k(boot)ro,0x1C0000(kernel),-(root)

The only tricky part was figuring out the above name
(phys_mapped_flash).  From reading the documentation, I thought I
could leave the name blank, but did not work for me.
 
>   i need to be able to concatenate 2 16M chips into a single 32M
> address space, then partition into 5 or 6 partitions.  am i being too
> optimistic about not needing my own driver map program if i can use
> the "generic" one?

I have not used the above with multiple chips.  MTD layer does have a 
CONFIG_MTD_CONCAT config parameter ...

Cliff

-- 
=======================
Cliff Brake
http://bec-systems.com