linux-kernel - Re: [PATCH V4 1/3] mtd: add new fields to nand_flash

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Message-ID: <CAMiH66HyH7tQG96UMKed6prpqBa=sgyntdO1pf0yG+=qyigY0Q@mail.gmail.com>
Date:	Wed, 13 Mar 2013 21:04:16 +0800
From:	Huang Shijie <shijie8@...il.com>
To:	artem.bityutskiy@...ux.intel.com
Cc:	Huang Shijie <b32955@...escale.com>, dwmw2@...radead.org,
	computersforpeace@...il.com, linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 1/3] mtd: add new fields to nand_flash_dev{}

On Wed, Mar 13, 2013 at 6:54 PM, Artem Bityutskiy
<artem.bityutskiy@...ux.intel.com> wrote:
> On Thu, 2013-03-07 at 18:49 +0800, Huang Shijie wrote:
>> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
>> index 591eeeb..f0a9d93 100644
>> --- a/include/linux/mtd/nand.h
>> +++ b/include/linux/mtd/nand.h
>> @@ -578,6 +578,8 @@ struct nand_chip {
>>   * @erasesize: eraseblock size in bytes (determined from the extended ID if 0)
>>   * @chipsize: total chip size in MiB
>>   * @options: stores various chip bit options
>> + * @id_len: The valid length of the @id.
>> + * @oobsize: OOB size
>>   */
>>  struct nand_flash_dev {
>>       char *name;
>> @@ -592,6 +594,8 @@ struct nand_flash_dev {
>>       unsigned long chipsize;
>>       unsigned long erasesize;
>>       unsigned long options;
>> +     unsigned long id_len;
>> +     unsigned long oobsize;
>>  };
>
> Why are these of type 'long', which is 64 bits in 64-bit architectures,
> which seems to be unnecessarily big. Wouldn't 'unsigned int' be enough?
>
Frankly speaking, "uint16_t" is enough.
"unsigned int" is too long for both the fields.

> Also, can we avoid having the 'id_len' field? Can the end of the

For these 4 toshiba nand, we do not need the id_len field.

> sequence of ID's be marked with a '0' or '0xFF' marker instead?

Are you sure that 0 or 0xff are not the valid data during the 8byte id data?
I am not sure.

Maybe in future, we may meet a nand which use the 0xff as a valid id-data.

But we can remove this id_len field now. It's ok to me.

thanks
Huang Shijie

>
> --
> Best Regards,
> Artem Bityutskiy
>
> --
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