OF compatible MTD platform RAM driver ?

[Laurent Pinchart <laurentp@cse-semaphore.com>]

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Hi everybody,

as part of a ARCH=ppc to ARCH=powerpc migration process, I'm looking for an 
OpenFirmware compatible way to handle a RAM-based MTD device.

On the platform_device based ppc architecture, the drivers/mtd/maps/plat-ram.c 
driver handled "mtd-ram" platform devices. There is no such driver for the 
OF-based powerpc architecture.

As a temporary workaround I hacked the physmap_of driver to 
handle "direct-mapped" OF devices oh type "ram" by adding a corresponding 
entry in the of_flash_match[] array. This seems to work fine.

What would be the preferred way to handle OF-compatible RAM-based MTD 
devices ? The 3 ways I can think of are

1. porting the plat-ram driver to OF (the driver isn't used in the kernel tree 
but I suspect it is used by out-of-tree boards)

2. creating a new plat-ram-of driver, much like the physmap_of driver comes 
from the physmap driver

3. extending the physmap_of driver to handle RAM devices (in which case 
references to "flash" in the function names should probably be replaced 
by "mtd")

I live option 3 better so far.

Has anyone already worked on this ? Is there any defined device tree mapping 
for MTD RAM devices ?

Best regards,

-- 
Laurent Pinchart
CSE Semaphore Belgium

Chaussée de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
F +32 (2) 387 42 75

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