Re: How can I prevent MTD to access the end of a flash device ?

From: Nicolas Pitre
Date: Tue Nov 22 2005 - 10:53:16 EST

On Tue, 22 Nov 2005, Franck wrote:

> Hi,
> I have two questions that I can't answer by my own. I tried to look at
> FAQ and documentation on MTD website but found no answer.

Please consider using the MTD mailing list next time (you certainly read
about it on the MTD web site).

> First question is about size of flash. I have a Intel strataflash
> whose size is 32MB but because of a buggy platform hardware I can't
> access to the last 64KB of the flash. How can I make MTD module aware
> of this new size. The restricted map size is initialized by my driver
> but it doesn't seem to be used by MTD.

The easiest thing to do is to define MTD partitions, the last one being
the excluded flash area.

> The second question is about the "cacheable" mapping field in map_info
> structure. I looked at others drivers and this field seems to be
> optional.

It is.

> Does this field, if set, improve flash access a lot ?

Yes. It was tested on ARM only though. Some architectures like i386
for example might need special tricks to implement this.

> Should I set up a cacheable mapping ?

Consider the comment for the inval_cache method in
include/linux/mtd/map.h and look at lubbock-flash.c for example.

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