Message-ID: <CAP1dx+xZ=FXtmTZ5YhJ4V6OLzFK5dwmLC2+jrfTK00QRKgCbEw@mail.gmail.com>
Date:	Wed, 20 Feb 2013 14:01:58 +0800
From:	Dong Aisheng <dong.aisheng@...aro.org>
To:	Alexander Shiyan <shc_work@...l.ru>
Cc:	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re: Re[8]: [PATCH v3] mfd: syscon: Add non-DT support

On 20 February 2013 13:41, Alexander Shiyan <shc_work@...l.ru> wrote:
>> > ...
>> >> >> >> >>  struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
>> >> >> >> >>  {
>> >> >> >> >>       struct device_node *syscon_np;
>> >> >> >> >>       struct regmap *regmap;
>> >> >> >> >> +     struct syscon *syscon;
>> >> >> >> >> +     struct device *dev;
>> >> >> >> >>
>> >> >> >> >>       syscon_np = of_find_compatible_node(NULL, NULL, s);
>> >> >> >> >> -     if (!syscon_np)
>> >> >> >> >> +     if (syscon_np) {
>> >> >> >> >> +             regmap = syscon_node_to_regmap(syscon_np);
>> >> >> >> >> +             of_node_put(syscon_np);
>> >> >> >> >> +
>> >> >> >> >> +             return regmap;
>> >> >> >> >> +     }
>> >> >> >> >> +
>> >> >> >> >> +     /* Fallback to search by id_entry.name string */
>> >> >> >> >> +     dev = driver_find_device(&syscon_driver.driver, NULL, (void *)s,
>> >> >> >> >> +                              syscon_match_id);
>> >> >> >> >> +     if (!dev)
>> >> >> >> >>               return ERR_PTR(-ENODEV);
>> >> >> >> >>
>> >> >> >> >> -     regmap = syscon_node_to_regmap(syscon_np);
>> >> >> >> >> -     of_node_put(syscon_np);
>> >> >> >> >> +     syscon = dev_get_drvdata(dev);
>> >> >> >> >>
>> >> >> >> >> -     return regmap;
>> >> >> >> >> +     return syscon->regmap;
>> >> >> >> >>  }
>> >> >> >> >>  EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);
>> >> >> >> >
>> >> >> >> > Since you are not actually comparing the "compatible" property here,
>> >> >> >> > I would suggest adding another function here,
>> >> >> >>
>> >> >> >> Yes, i also think like that.
>> >> >> >
>> >> >> > In this case we should provide two paths for drivers which can work as with DT
>> >> >> > and without DT.
>> >> >>
>> >> >> Yes.
>> >> >
>> >> > I still think the universal procedure is better for the driver.
>> >> >
>> >>
>> >> Why?
>> >> I did not see your reply on my other comments on the problems of using universal
>> >> procedure?
>> >> Please let me know if you think they're not issues.
>> >
>> > Yes, I do not see a problem here.
>> > I will try to show the code.
>> >
>> > In the driver:
>> > struct regmap *r;
>> > r = syscon_regmap_lookup_by_compatible("my_super_syscon");
>> >
>> > For DT case:
>> > syscon@...456 {
>> >   compatible = "my_super_syscon", "syscon";
>> >   ...
>> > };
>> >
>> > For non-DT case:
>> > struct platform_device_id id = { .name = "my_super_syscon", };
>> > struct platform_device syscon_pdev = {
>> >   .name = "syscon",
>> >   .id_entry = &id,
>>
>> This is really strange to me and i've never seen such using.
>> Usually the id_table is provided by the driver and the match process then will
>> set the correct id_entry for the platform device once it matches.
>> Please see the platform_bus match process: drivers/base/platform.c
>
> Yes, this is non-standard usage. Currently we do not have platform_device_id
> entries for a "syscon" driver, so this field is untouched for a platform device
> and we can use it. At least this works, but, of course, more experts should
> fix me on this question if I think incorrect.
>

Hmm, i'm afraid most people may not accept this.
The platform_device_id are not desgined for such using, i guess.

>>
>> >   ...
>> > };
>> > platform_device_register(&syscon_pdev);
>> >
>> > Do I understand what you mean?
>> >
>>
>> My understanding for non-dt case is something like:
>> In client driver:
>> struct regmap *r;
>> r = syscon_regmap_lookup_by_pdevname("my_super_syscon");
>>
>> In board code:
>> struct platform_device syscon_pdev = {
>> .name = "my_super_syscon",
>> ...
>> };
>>  platform_device_register(&syscon_pdev);
>>
>> In syscon driver:
>> static struct platform_device_id syscon_device_ids[] = {
>>         {
>>                 .name = "my_super_syscon",
>>         }, {
>>                 /* sentinel */
>>         }
>> };
>> MODULE_DEVICE_TABLE(platform, syscon_device_ids);
>>
>> static struct platform_driver syscon_driver = {
>>         .driver = {
>>                 .name = "syscon",
>>                 .owner = THIS_MODULE,
>>                 .of_match_table = of_syscon_match,
>>         },
>>         .id_table       = syscon_device_ids,
>>         .probe          = syscon_probe,
>>         .remove         = syscon_remove,
>> };
>>
>> One problem is that every user needs to add their syscon compatible device
>> support(platform_device_id) in syscon driver first before they can use it.
>> But it looks to me just like how other driver generally does.
>
> I agree, this is a more proper way, but in this case we should create a big table
> here with records for each device...
>

Only non-dt needs add it which may not be so many and you're the first one.

Regards
Dong Aisheng
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