Re: [PATCH V3 3/6] MTD : add the database for the NANDs

[Huang Shijie <b32955@freescale.com>]

Hi Brian:
> Hi,
>
> I see nothing has happened with this thread recently. It doesn't
> deserve to die though.
>
> On Thu, Mar 31, 2011 at 10:17 AM, Huang Shijie<shijie8@gmail.com>  wrote:
>> 2011/3/31 Artem Bityutskiy<dedekind1@gmail.com>:
>>>>> If you have new chips to support in the future, you should add them in
>>>>> drivers/mtd/nand/nand_ids.c and not keep this file.
>>>>>
>>>> The data structure  nand_flash_dev{} does not contain enough information.
>>>> So I want to the nand_device_info{} to replace it in future.
>>> Just add this information, if it is of generic nature (like SLC/MLC
>>> flag, required ECC strength, etc).
> Are SLC/MLC and ECC strength necessary to track? I don't see a good
We do not necessary  to track it.  For normal nand, I can compute it 
myself ,
just as the current driver does; for ONFI nand ,we should parse it out 
from the Parameter Page.
It need an extra patch to do this.
> benefit to cost ratio of trying to detect ECC strength especially,
> since the levels specified in data sheets vary without much pattern
> and nobody provides a way for decoding this from ID; do you really
> want to have to make separate chip entries for every single chip that
> comes around?
>
>>>>> I still do not understand why this would be needed, is it because the generic
>>>>> code does not provide enough informations for your driver?
>>>>>
>>>> yes.
>>>>
>>>> IMHO, the generic code is somehow trapped in a wrong way. :(
> I may agree, but can you be more specific on the trap?
>
>>>> Paring the id bytes is not sufficient to get all the information you
>>>> need which is faced by me.
> What's an alternative to "paring the id bytes"?
>
>>>> What's more, I think the paring code is ugly, see the nand_get_flash_type().
>>> You are welcome to fix this. There is _a lot_ of ugly code in MTD
>>> because no one loves it. Give it some love :-)
> While I agree that a lot of this is ugly, it is mostly a matter of
> necessity. NAND manufacturers do not have a standard (ONFI doesn't
> really count, since there's basically 1 manufacturer using it), and so
> the most "generic" code is to have different code paths for different
> manufacturers (often with exceptions to each rule, since even a single
> manufacturer changes its standards arbitrarily). Then you find
> manufacturers like Toshiba that recently don't have any (published)
> pattern at all for detecting OOB size generically.
bad news.  I do not have such chip yet, If i have , i will test it, and 
change the current MTD code.
> Thus, it seems to me like we will need some form of the approach
> provided by Huang. As I've found, there are some things that just
> can't be decoded from the ID these days, so our ID table will need to
> be able to track:
> * full ID string (not just the 2nd byte "Device ID")
> * relevant bad block scanning options
>
> FWIW, we already implement an exception table in our own driver that
> includes the above 2 items, for chips that can't be handled with the
> table/detection structure as-is. We don't particularly need SLC/MLC
> but I don't object to recording it if we can determine it reliably,
> and while ECC level could be useful, it is difficult to discover
> generically, as I mentioned above.
>
I do not use the SLC/MLC info now.
>>>> Why not create a new database which contains all the necessary
>>>> information for a nand, and can be easy
>>>> find by the id bytes as the keyword?
>>> You can create this database by extending/improving/cleaning up the
>>> existing code base with a nice series of patches.
>>>
>> ok. I will try to fix the generic code before my driver is submitted.
> What happened to this statement? I see that your driver was submitted,
> but no efforts were made for chip detection cleanup. Were you
> satisfied with the current detection?
When i am free, I will change the current code. But i am a little busy 
now :(



Best Regards
Huang Shijie
> While we're on the subject, I'll direct your attention to this NAND
> data table that I've worked on. It should provide a decent summary of
> most of the data sheets I have sorted through. It should also show you
> that certain things are going to be very hard to detect (e.g., ECC
> level). It should also show that while some chips are not supported by
> standard code (e.g., weird bad block scanning features that haven't
> been supported, non-standard OOB sizes with no given pattern in the
> datasheets), the vast majority of the chips I've come across should be
> detected properly:
>
> http://linux-mtd.infradead.org/nand-data/nanddata.html
>
> And of course, please contribute to
> git://git.infradead.org/mtd-www.git if you have additions or edits for
> the table. It's not perfect, but it can help for sorting through
> different chips.
>
> Brian
>