Preferred way to configure MTD physical mapping and partitioning

Preferred way to configure MTD physical mapping and partitioning

[Laurent Pinchart]

Hi everybody,

while browsing the kernel sources to find out how other boards configure MTD 
physical mapping and partitioning, I noticed that a couple of different 
approaches were possible:

- adding a board specific "driver" in drivers/mtd/maps and handle all mapping 
manually
- adding board specific MTD configuration in arch/ppc/platforms with calls to 
physmap_set_partitions() and physmap_configure()
- adding board specific MTD configuration in arch/ppc/platforms with a call to 
physmap_set_partitions(), and using the CONFIG_MTD_PHYSMAP option with 
physical mapping values provided in the kernel configuration.

Could anyone comment on the preferred approach ?

Best regards,

Laurent Pinchart

Preferred way to configure MTD physical mapping and partitioning

[Thiago Galesi]

What about configuring it in kernel configuration (using make
menuconfig for example). Most of the configurations can be done
through there (position, size, width, etc)?

Only if you have something out of the ordinary it would be advisable
to use a driver.

If you give us more detail we'll be able to help you better

BTW, you can partition your flash via cmdline

Cheers :)



-- 
-
Thiago Galesi

Preferred way to configure MTD physical mapping and partitioning

[Thiago Galesi]

> >
> > BTW, you can partition your flash via cmdline
>
> So would that be the preferred way to configure MTD partitions ?
>
> Laurent Pinchart
>
Using the mtdparts option in the boot cmdline. example

mtdparts=256k(partition1)ro,333k(partition2),444k(partition3),-(partition 4)

This will create /dev/mtd1, /dev/mtd2, etc, etc (and the corresponding
mtdblock devices) - you still have to create the inodes manually
(AFAIK) with the corresponding size, etc Using the '-' in the last
option uses all the remaining space. (as the ro option that makes the
partition read only. Useful for not overwriting your bootloader)

-- 
-
Thiago Galesi

RE: Preferred way to configure MTD physical mapping and partitioning

[Guillaume Autran]

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Hi Laurent,

There is also the "RedBoot" approach that let you create and store your partition table in a reserved sector of your flash.
You can enable your kernel to parse and create your MTD partitions according. After that, all you need to do is make your boot loader write the table in flash. Have a look at the file "linux/drivers/mtd/redboot.c". 

Guillaume.



-----Original Message-----
From: linuxppc-embedded-bounces+gautran=mrv.com@ozlabs.org on behalf of Laurent Pinchart
Sent: Mon 5/22/2006 6:32 AM
To: linuxppc-embedded@ozlabs.org
Subject: Preferred way to configure MTD physical mapping and partitioning
 
Hi everybody,

while browsing the kernel sources to find out how other boards configure MTD 
physical mapping and partitioning, I noticed that a couple of different 
approaches were possible:

- adding a board specific "driver" in drivers/mtd/maps and handle all mapping 
manually
- adding board specific MTD configuration in arch/ppc/platforms with calls to 
physmap_set_partitions() and physmap_configure()
- adding board specific MTD configuration in arch/ppc/platforms with a call to 
physmap_set_partitions(), and using the CONFIG_MTD_PHYSMAP option with 
physical mapping values provided in the kernel configuration.

Could anyone comment on the preferred approach ?

Best regards,

Laurent Pinchart
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Re: Preferred way to configure MTD physical mapping and partitioning

[David Woodhouse]

On Mon, 2006-05-22 at 12:32 +0200, Laurent Pinchart wrote:
> - adding a board specific "driver" in drivers/mtd/maps and handle all mapping 
> manually
> - adding board specific MTD configuration in arch/ppc/platforms with calls to 
> physmap_set_partitions() and physmap_configure()
> - adding board specific MTD configuration in arch/ppc/platforms with a call to 
> physmap_set_partitions(), and using the CONFIG_MTD_PHYSMAP option with 
> physical mapping values provided in the kernel configuration.
> 
> Could anyone comment on the preferred approach ?

None of the above. The physmap driver in the MTD git tree already works
with a platform_device, instead of needing a call to physmap_configure()
or manual configuration at build time. Either register a
platform_device, or preferably extend it to use an of_device too.

-- 
dwmw2