how to adress flash memory in Linux

[Ming Liu]

Dear Peter,
Thank you so much and what you said is really what I want! It's really 
helpful. But I still have some questions:

>Next you need a mapping driver. You may either use the generic physmap
>driver and supply your partitions too it or write your own mapping driver.
>This is not very complicated. For examples look under drivers/mtd/maps.

I have enabled the "CFI Flash device in physical memory map" and provided 
the start address and length. Now my system could recognize the flash 
chip.(My chip is CFI Intel/Strata compatible) Could you please say 
something in detail on how to supply my partitions to the physmap driver? 
Shall I do that during kernel configuration or just in Linux?

>Once you got a chip driver and a mapping driver you need to create the
>appropriate device nodes. E.g.:
>
>mknod -m 644 $XROOT/dev/mtd0    c 90 0
>mknod -m 644 $XROOT/dev/mtdr0   c 90 1
>mknod -m 644 $XROOT/dev/mtd1    c 90 2
>mknod -m 644 $XROOT/dev/mtdr1   c 90 3
>mknod -m 644 $XROOT/dev/mtd2    c 90 4
>mknod -m 644 $XROOT/dev/mtdr2   c 90 5
>
>mkdir -p $XROOT/dev/mtdblock
>mknod -m 644 $XROOT/dev/mtdblock/0 b 31 0
>mknod -m 644 $XROOT/dev/mtdblock/1 b 31 1
>mknod -m 644 $XROOT/dev/mtdblock/2 b 31 2
>

I am some confused that what's the difference between the mtd character 
device and the block device. Under which circumstance shall I use mtd char 
or block. In my mind, I think the flash memory device is more like a block 
device and most operations, such as block write and block read, are block 
device operations. Then what's the use for the mtd character device? Sorry 
that I have read the FAQ in MTD website but I cannot understand this very 
well.

Thank you so so so much for your kindly help.

Regards
Ming

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