Subject: Re: [PATCH] powerpc: Create "rom" (MTD) device prpmc2800

From: Sergei Shtylyov <[email-masked]>
Date: Sun, 03 Jun 2007 20:10:18 +0400

Hello.

Benjamin Herrenschmidt wrote:
> On Fri, 2007-06-01 at 23:30 -0500, Milton Miller wrote:
> 
>>Actually, looking back at your device tree {1], your list several
>>properties for flash, including bank-width and partition names.
>>Perhaps first compatible should be direct-mapped-partitioned-flash,
>>direct-mapped-partitioned-rom, direct-mapped-rom  (to me a
>>direct-mapped-rom driver would expose one section of address space
>>read-only). I'm assuming that your driver for this "direct-mapped"
>>device will look at these properties from the of device node and
>>call the mtd layer somewhat directly with their contents. 

> If it's a flash, compatible should be the chip type, and maybe as a
> second entry, what type of flash protocol (amd, intel, cfi, ...) it's
> compatible.

    As I've already (and repatedly) stated before, this gets you *nothing* WRT 
selecting the proper driver in the current Linux MTD subsystem. What it 
actually *needs* to know is flash mapping information, the CFI/JEDEC interface 
then can be deduced by probing -- so, this property ("ptobe-type"), although 
specified in Documentation/powerpc/booting-without-of.txt, is optional.

> Ben.

WBR, Sergei