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SubjectRe: [PATCH v4 07/15] mtd: nand: move Samsung specific init/detection logic in nand_samsung.c
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On 01/11/2017 08:57 AM, Boris Brezillon wrote:
> On Tue, 10 Jan 2017 20:00:28 +0100
> Marek Vasut <marek.vasut@gmail.com> wrote:
>
>> On 01/07/2017 08:49 AM, Boris Brezillon wrote:
>>> On Sat, 7 Jan 2017 00:53:24 +0100
>>> Marek Vasut <marek.vasut@gmail.com> wrote:
>>>
>>>> On 01/04/2017 06:08 PM, Boris Brezillon wrote:
>>>>> On Wed, 4 Jan 2017 16:14:07 +0100
>>>>> Marek Vasut <marek.vasut@gmail.com> wrote:
>>>>>
>>>>>> On 01/03/2017 02:01 PM, Boris Brezillon wrote:
>>>>>>> Move Samsung specific initialization and detection logic into
>>>>>>> nand_samsung.c. This is part of the "separate vendor specific code from
>>>>>>> core" cleanup process.
>>>>>>>
>>>>>>> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
>>>>>>
>>>>>> [...]
>>>>>>
>>>>>>> diff --git a/drivers/mtd/nand/nand_ids.c b/drivers/mtd/nand/nand_ids.c
>>>>>>> index b3a332f37e14..05e9366696c9 100644
>>>>>>> --- a/drivers/mtd/nand/nand_ids.c
>>>>>>> +++ b/drivers/mtd/nand/nand_ids.c
>>>>>>> @@ -10,7 +10,7 @@
>>>>>>> #include <linux/mtd/nand.h>
>>>>>>> #include <linux/sizes.h>
>>>>>>>
>>>>>>> -#define LP_OPTIONS NAND_SAMSUNG_LP_OPTIONS
>>>>>>> +#define LP_OPTIONS 0
>>>>>>> #define LP_OPTIONS16 (LP_OPTIONS | NAND_BUSWIDTH_16)
>>>>>>>
>>>>>>> #define SP_OPTIONS NAND_NEED_READRDY
>>>>>>> @@ -169,10 +169,12 @@ struct nand_flash_dev nand_flash_ids[] = {
>>>>>>> };
>>>>>>>
>>>>>>> /* Manufacturer IDs */
>>>>>>> +extern const struct nand_manufacturer_ops samsung_nand_manuf_ops;
>>>>>>
>>>>>> Is the extern needed ?
>>>>>
>>>>> Yes, unless you have another solution. If you remove the extern keyword
>>>>> you just redeclare samsung_nand_manuf_ops here, which is not what we
>>>>> want.
>>>>
>>>> Maybe some accessor function can help ?
>>>>
>>>
>>> You mean, in nand_ids.c
>>>
>>> const struct nand_manufacturer_ops *get_samsung_nand_mafuf_ops();
>>>
>>> struct nand_manufacturers nand_manuf_ids[] = {
>>> ...
>>> {NAND_MFR_SAMSUNG, "Samsung", get_samsung_nand_mafuf_ops},
>>> ...
>>> };
>>>
>>> and then, in nand_samsung.c
>>>
>>> const struct nand_manufacturer_ops *get_samsung_nand_mafuf_ops()
>>> {
>>> return &samsung_nand_mafuf_ops;
>>> }
>>
>> Yeah, something like that.
>>
>>> What's the point of this extra indirection? I mean, in both cases you
>>> use a symbol that is not part of the same source file, so you'll have
>>> to define this symbol (using a function prototype or an extern object
>>> definition).
>>> Is this all about fixing checkpatch warnings, or do you have a problem
>>> with objects shared between different source files?
>>
>> The later, separating this with an accessor function feels a bit cleaner
>> to me than using extern foo.
>>
>>> Now, I agree that the current approach is not ideal. A real improvement
>>> would be to let the NAND manufacturer drivers (nand_<vendor>.c) register
>>> themselves to the core. Something similar to CLK_OF_DECLARE() or
>>> IRQCHIP_DECLARE() for example. But that means creating a dedicated
>>> section for the nand_manufs_id table, and it's a lot more invasive than
>>> the current approach.
>>
>> Well this would be awesome, but this can also be done later. I presume
>> you'll get to it eventually anyway, as soon as you'll be annoyed enough
>> with the current ugly-ish implementation.
>>
>
> If we plan to rework it this way, I'd like to keep the existing
> approach (with the extern) to avoid changing the prototype of
> nand_manufacturer once again when we rework the nand_manufacturer
> registration logic.
>
> Also note that in v6 I'm keeping a pointer to the nand_manfucturer
> object in nand_chip, so that if we ever need to print the manufacturer
> name we don't have to search again in the NAND manufacturer table.
> After this rework, I no longer store the manufacturer_ops directly in
> nand_chip, and have to access them by doing
> chip->manufacturer.desc->ops->xxx.
>
> Which means, with your solution, I'll have to do
>
> ops = nand_get_manufacturer_ops(chip->manufacturer.desc);
> ops->xxx();
>
> instead of
>
> chip->manufacturer.desc->ops->xxx();
>

All right, I think we can live with this either way.

--
Best regards,
Marek Vasut

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