linux-kernel - RE: [PATCH v3 3/5] drivers: regulator: Add ADI MAX77541/MAX77540 Regulator Support

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Message-ID: <BY5PR03MB5153A0972FD89DA362813F06E7D09@BY5PR03MB5153.namprd03.prod.outlook.com>
Date:   Tue, 31 Jan 2023 14:38:33 +0000
From:   "Sahin, Okan" <Okan.Sahin@...log.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC:     Lee Jones <lee@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        ChiYuan Huang <cy_huang@...htek.com>,
        "Bolboaca, Ramona" <Ramona.Bolboaca@...log.com>,
        Caleb Connolly <caleb.connolly@...aro.org>,
        William Breathitt Gray <william.gray@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>
Subject: RE: [PATCH v3 3/5] drivers: regulator: Add ADI MAX77541/MAX77540
 Regulator Support

On Tue, 31 Jan 2022 4:30 PM
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

>On Tue, Jan 31, 2023 at 01:59:45PM +0000, Sahin, Okan wrote:
>> On Tue, 31 Jan 2022 4:30 PM
>> Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
>> >On Tue, Jan 31, 2023 at 01:23:33PM +0000, Sahin, Okan wrote:
>> >> On Tue, 31 Jan 2022 3:27 PM
>> >> Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
>> >> >On Tue, Jan 31, 2023 at 09:27:48AM +0000, Sahin, Okan wrote:
>
>...
>
>> >> >> Sorry for second question. I do not want to bother you, but I
>> >> >> realized that I need to be sure about driver_data before sending
>> >> >> new patch. You said that you need to use pointers directly for
>> >> >> driver_data then I fixed that part in mfd, but I do not need or
>> >> >> use driver_data in regulator since chip_id comes from mfd device
>> >> >> so I think using like below should be enough for my implementation.
>> >> >>
>> >> >> static const struct platform_device_id
>> >> >> max77541_regulator_platform_id[] =
>> >{
>> >> >> 	{ "max77540-regulator", },
>> >> >> 	{ "max77541-regulator", },
>> >> >> 	{  /* sentinel */  }
>> >> >> };
>> >> >> MODULE_DEVICE_TABLE(platform, max77541_regulator_platform_id);
>> >> >>
>> >> >> static const struct of_device_id max77541_regulator_of_id[] = {
>> >> >> 	{ .compatible = "adi,max77540-regulator", },
>> >> >> 	{ .compatible = "adi,max77541-regulator", },
>> >> >> 	{ /* sentinel */  }
>> >> >> };
>> >> >> MODULE_DEVICE_TABLE(of, max77541_regulator_of_id);
>> >> >>
>> >> >> What do you think?
>> >> >
>> >> >If you have got all necessary data from the upper layer, why do
>> >> >you need to have an ID table here? I'm not sure I understand how
>> >> >this OF ID table works in this case.
>> >
>> >> I added it since there is regulator node in device tree. With the
>> >> help of devm_regulator_register(..), driver takes parameters of
>> >> regulator node. I also used id to select and to initialize
>> >> regulator descriptors which are chip specific. So far there is no
>> >> comment about OF ID table so I kept it. I thought I need to add
>> >> both of id table and platform id table as name matching is required to
>initialize platform device from mfd.
>> >
>> >For platform device is one mechanism how to enumerate device, and
>> >bind it to the driver. The OF ID table needs to be present in case
>> >you are using it for direct DT enumeration (there is also something
>> >related to MFD child nodes, but you need to check and explain how your
>device is enumerated by this driver).
>> >
>> >I.o.w. please clarify how the OF ID table is being used.
>>
>> I do not use "of id table" directly in max77541-regulator.c so do I need to
>exclude it?
>
>Exactly my point. How does this OF ID table affect the device enumeration?
>
Since this is sub-device, it seems OF ID table does not affect the device enumarion, but as I stated before, I thought I need to add OF ID table because regulator's parameters are initialized via DT with the help of devm_regulator_register(..). It scans all the nodes under regulators node.
>> However, devm_regulator_register(..) method initialize each regulator
>> with the nodes under "regulators node". If of_match in desc and name
>> of node matches, then regulator will be initialized with parameters in
>> the node under the regulators node in the device tree. Since I am
>> using device tree to initialize regulators, I added of id table. I
>> hope I explained the situation clearly.
>
>This is confusing. If your regulator is enumerated via DT, why do you need MFD?
MAX77541 has also adc that is why I added MAX77541 as mfd device
>
>--
>With Best Regards,
>Andy Shevchenko
>
Hi Andy,

Thank you for your support and your time.

Regards,
Okan Sahin