On Monday 06 July 2009 10:37:10 Mike Frysinger wrote:
On Monday 06 July 2009 03:25:43 Stefan Roese wrote:
On Monday 06 July 2009 09:04:44 Mike Frysinger wrote:
I kind of like the idea to create a new set of commands for accessing such board specific NOR FLASH (can be used on "normal" NOR FLASH as well). Perhaps we could make it "generic" in a way that it can be used for all kind of "MTD devices". How about this "mtd" commandset:
Select MTD NOR device #1 (2nd NOR device): => mtd device nor 1
Or via mtdparts/mtdids: => mtd device nor0
so both syntaxes would be available when mtdparts support is enabled, or would it be one or the other ?
I didn't make my mind up until now. I was just throwing out an idea.
we would want to avoid ambiguity -- is "nor" referring to the nor flashes or is it referring to a partition named "nor".
The first version would refer "nor" as flash type and the 2nd one "nor0" as a device name from mtdparts/mtdids.
so people wouldnt be able to name a mtdpart "nor"
Yes, this doesn't make much sense. It's probably better to only use the 2nd approach via the mtdparts/mtdids name.
what flash devices does mtdparts support now ? i'm not really familiar with it and the README and doc/ files doesnt seem to cover it.
Right now it supports NAND, OneNAND and NOR (if CONFIG_FLASH_CFI_MTD is enabled). Others can be easily added (see drivers/mtd/cfi_mtd.c for NOR).
so FLASH_CFI_MTD is merely glue between the existing CFI flash driver and the MTD layers ?
Correct. And such glue layers could be added for other FLASH technologies like SF as well.
i guess each flash type would parse the additional commands however it liked and so the mtd command would just act as a multiplexer at this point. the current spi flash "sf" command is pretty flexible -- you specify the spi chip select to select the device and you can specify other parameters dynamically (like frequency). so when folding it in, we'd have: => mtd device sf <cs> [speed] [mode]
common/cmd_mtd.c common/cmd_mtd_sf.c common/cmd_mtd_nor.c
I was more thinking about adding the MTD layer to all FLASH types supported by this new commandset. Then accessing the device is done via the MTD functions pointers (mtd->erase, mtd->read, etc). Special FLASH type specific stuff still needs to be handled in some additional drivers (like OOB handling for NAND/OneNAND, or SF specific stuff) though.
ok, this seems like it should be doable in a gradual progression. i.e. today i am only concerned with nor flash, so getting a base framework with that as the only supported flash should be fine. once we know it can replace the existing cmd_flash.c functions, we can look at folding in other flash types. -mike
I think this is a doable approach. But we first need a general consent on this. Other opinions on this are welcome...
Best regards, Stefan
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