Re: [PATCH V3 1/3] mtd: add new fields to nand_flash_dev{}

[Huang Shijie]

ä 2013å03æ02æ 22:21, Artem Bityutskiy åé:
> On Sat, 2013-02-16 at 11:56 +0800, Huang Shijie wrote:
> > On Tue, Feb 12, 2013 at 11:47 PM, Artem Bityutskiy<dedekind1@xxxxxxxxx>  wrote:
> > > On Mon, 2013-01-28 at 12:57 +0800, Huang Shijie wrote:
> > > > +       {"SmartMedia 256MiB 3,3V",      {0, 0x71}, 512, 256, 0x4000 },
> > > > +       {"SmartMedia 256MiB 3,3V ROM",  {0, 0x5b}, 512, 256, 0x4000,
> > > > NAND_ROM},
> > > Sorry for a possibly stupid question, but what does it buy you adding
> > > another "0" to all the entries? I see you add another table, which you
> > > look up if the "traditional" table does not work. Why you need to add
> > > these zeroes?
> > The zeros are for the maf_id.
> >
> > The dev_id is the second byte of the 8-byte id data.
> It does not really make me understand why we add these zeroes, they
> still look useless to me... Would you please be a little more verbose
> about your solution?
the 8bytes id data read out by the READ ID command is in the following 
order:
   byte 0(Maker id): such as 0x98 stands for Toshiba, 0xec stands for 
Samsung.
   byte 1(device id):
   byte 2(used to store the chip number,cell type information):
   byte 3(used to store the page size, block size information)
   byte 4(used to store the Plane information).
   ........................


The current code uses the @id to store the device id(byte 1).
But if we use the 8 bytes id data as the keyword, and expand the @id 
field to 8byte array,
the device id is the second byte now. All the added zeros are for the 
Maker id.
For example,
    {"SmartMedia 256MiB 3,3V",      {0, 0x71}, 512, 256, 0x4000 },

We really do not use the zeros. All the zeros are added for avoiding the 
misunderstanding.
If we do not add the zero, it will looks like:

     {"SmartMedia 256MiB 3,3V",      {0x71}, 512, 256, 0x4000 },

The device id (0x71) becomes the first byte of 8byte id array, people will treat the 0x71 as the Maker code.


thanks
Huang Shijie


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